Description:DESCRIPTION:
Field of the invention:
[0001] The present disclosure generally relates to the technical field of nanotechnology and, in particular, relates to a novel and efficient method for azlactones synthesis through microwave irradiation using zirconium (Zr) and phosphorus (P) co-doped titanium dioxide (TiO2) nano photocatalyst, thereby achieving efficient yields in significantly shorter time intervals.
Background of the invention:
[0002] Nanoscience and nanotechnology have made significant progress over the past decade. Many studies have demonstrated that nano catalysts offer impressive performance in terms of selectivity, reactivity, and increased product yields. The nanoparticles provide more active sites per unit area compared to their larger counterparts due to their high surface-to-volume ratio. Traditional homogeneous catalysis has limitations such as instability, non-recyclability of the catalyst, and the use of expensive and hazardous reagents, which often result in lower yields of the desired products.

[0003] Recently, nanoparticles have gained attention as potential heterogeneous nano photocatalysts due to their superior properties compared to bulk materials. Nano metal oxides, in particular, have intrigued researchers because of their outstanding physical and chemical catalytic capabilities. Nano titanium dioxide (nano-TiO2) is especially popular in various industrial applications related to catalysis. The nano-TiO2 is used for the selective reduction of nitrite or nitrate ions, photocatalysis in organic synthesis, pollutant removal, as well as in photovoltaic devices, sensors, and paints. Studies have highlighted the exceptional properties of nano-TiO2, such as high activity, non-toxicity, availability, reusability, strong oxidizing power, and long-term stability.

[0004] The synthesis of nano titania co-doped with zirconium and study its effectiveness as a photocatalyst in organic synthesis. The compound 5(4H)-oxazolones holds great importance in synthetic and medicinal chemistry, leading to increased interest in their synthesis and study. Specifically, 4-arylidene-2-phenyl-5(4H)-oxazolones are key intermediates in the production of various bioactive compounds, including antibiotics, analgesics, anti-inflammatory drugs, cancer treatments, diabetes medications, and antidepressants.

[0005] The synthesis of 4-arylidene-2-phenyl-5(4H)-oxazolones has long fascinated organic chemists due to their wide range of pharmacological and other applications. Recent advancements have explored the use of bismuth acetate and zinc chloride as promising methods for synthesizing 5(4H)-oxazolones. Additionally, current research has shifted towards multicomponent processes that create nitrogen-containing heterocyclic systems like pyridine and pyrimidine. The 4-Arylidene-2-phenyl-5(4H)-oxazolones, which are also known as azlactones. The azlactones are important intermediates in the synthesis of several small molecules.

[0006] Erlenmeyer-Plöchl azlactone synthesis is a classic method for the synthesis of azlactones, which are five-membered heterocyclic compounds containing a nitrogen atom and a carbonyl group. The reaction involves the condensation of an N-acyl glycine with an aldehyde in the presence of acetic anhydride. The reaction is typically carried out at high temperatures (100–150 °C) for several hours. The yield of the reaction can be moderate to good, depending on the specific reactants used.

[0007] The Erlenmeyer-Plöchl azlactone synthesis is a versatile method that can be used to synthesize a wide variety of azlactones. However, the reaction also has some drawbacks. One drawback of the Erlenmeyer-Plöchl azlactone synthesis is that it can be a messy reaction. The acetic anhydride used in the reaction is a powerful dehydrating agent, and it can cause side reactions such as the formation of ketenes. Another drawback of the Erlenmeyer-Plöchl azlactone synthesis is that it is not always selective. The reaction can sometimes produce multiple products, and it can be difficult to control the Regio chemistry of the reaction.

[0008] In existing technology, a novel and efficient method for synthesizing azlactones using zirconium (Zr) and phosphorus (P) co-doped titanium dioxide (TiO2) nano photocatalyst in the presence of visible light irradiation. The proposed method employs the zirconium (Zr) and phosphorus (P) co-doped TiO2 nano photocatalyst to enhance selectivity, thereby producing azlactones with minimal impurities and unwanted by products. However, the method requires at least 30-60 min for the azlactones synthesis.

[0009] By addressing all the above-mentioned problems, there is a need for a method for synthesizing azlactones through microwave irradiation using zirconium (Zr) and phosphorus (P) co-doped titanium dioxide (TiO2) nano photocatalyst, thereby achieving efficient yields in significantly shorter time intervals. There is also a need for method that reduces reaction times from at least 1-2 hr to just 3-5 min, thereby offering a substantial improvement over conventional method. There is also a need for method that utilizes a novel zirconium (Zr) and phosphorus (P) co-doped titanium dioxide (TiO2) nano photocatalyst, which achieves efficient yields at least 96 %, thereby ensuring high product purity and reducing the need for additional purification process.

[0010] There is also a need for method that utilizes a novel zirconium (Zr) and phosphorus (P) co-doped titanium dioxide (TiO2) nano photocatalyst, which offers increased catalytic activity due to its larger surface area and reduced band gap energy, thereby providing more efficient reactions with higher specificity and fewer side products. There is also a need for method that utilizes the novel zirconium (Zr) and phosphorus (P) co-doped titanium dioxide (TiO2) nano photocatalyst, which can be reused multiple times without losing activity, thereby making the process more sustainable and cost-effective. There is also a need for method that adheres to green chemistry principles by minimizing the use of toxic reagents and reducing waste, thereby making the process safer and more sustainable.

[0011] There is also a need for the method that lowers the overall cost of production, thereby making the process more economically viable for large-scale industrial applications. There is also a need for method that consumes significantly less energy than traditional heating methods, thereby resulting substantial energy savings and reduced operational costs. There is also a need for method that scales easily from laboratory to industrial production, thereby ensuring consistent quality and efficiency, and improving resource utilization and reducing manufacturing costs. There is also a need for an environmentally friendly method that generates less waste, thereby reducing waste management and disposal costs.
Objectives of the invention:
[0012] The primary objective of the present invention is to provide a method for synthesizing azlactones through microwave irradiation using zirconium (Zr) and phosphorus (P) co-doped titanium dioxide (TiO2) nano photocatalyst, thereby achieving efficient yields in significantly shorter time intervals.

[0013] Another objective of the present invention is to provide a method that reduces reaction times from at least 1-2 hr to just 3-5 min, thereby offering a substantial improvement over conventional method.

[0014] The other objective of the present invention is to provide a method that utilizes a novel zirconium (Zr) and phosphorus (P) co-doped titanium dioxide (TiO2) nano photocatalyst, which achieves efficient yields at least 96 %, thereby ensuring high product purity and reducing the need for additional purification process.

[0015] The other objective of the present invention is to provide a method that utilizes a novel zirconium (Zr) and phosphorus (P) co-doped titanium dioxide (TiO2) nano photocatalyst, which offers increased catalytic activity due to its larger surface area and reduced band gap energy, thereby providing more efficient reactions with higher specificity and fewer side products.

[0016] The other objective of the present invention is to provide a method that utilizes the novel zirconium (Zr) and phosphorus (P) co-doped titanium dioxide (TiO2) nano photocatalyst, which can be reused multiple times without losing activity, thereby making the process more sustainable and cost-effective.

[0017] The other objective of the present invention is to provide a method that adheres to green chemistry principles by minimizing the use of toxic reagents and reducing waste, thereby making the process safer and more sustainable.

[0018] The other objective of the present invention is to provide a method that lowers the overall cost of production, thereby making the process more economically viable for large-scale industrial applications.

[0019] The other objective of the present invention is to provide a method that consumes significantly less energy than traditional heating methods, thereby resulting substantial energy savings and reduced operational costs.

[0020] Yet another objective of the present invention is to provide a method that scales easily from laboratory to industrial production, thereby ensuring consistent quality and efficiency, and improving resource utilization and reducing manufacturing costs.

[0021] Further objective of the present invention is to provide an environmentally friendly method that generates less waste, thereby reducing waste management and disposal costs.
Summary of the invention:
[0022] The present disclosure proposes synthesis of azlactones through microwave irradiation using zirconium-phosphorus co-doped titanium oxide nano photocatalyst. The following presents a simplified summary in order to provide a basic understanding of some aspects of the claimed subject matter. This summary is not an extensive overview. It is not intended to identify key/critical elements or to delineate the scope of the claimed subject matter. Its sole purpose is to present some concepts in a simplified form as a prelude to the more detailed description that is presented later.

[0023] In order to overcome the above deficiencies of the prior art, the present disclosure is to solve the technical problem to provide a novel and efficient method for azlactones synthesis through microwave irradiation using zirconium (Zr) and phosphorus (P) co-doped titanium dioxide (TiO2) nano photocatalyst, thereby achieving efficient yields in significantly shorter time intervals.

[0024] According to one aspect, the invention provides a method for synthesizing azlactones. At one step, a p-substituted benzoic acid (1) is reacted with thionyl chloride (SOCl2) in the presence of dichloromethane (DCM) to obtain a viscous acid chloride (RCOCl) (2). The substituted benzoic acid is selected from at least one of p-substituted benzoic acid, m-substituted benzoic acid, and o-substituted benzoic acid. At one step, the viscous acid chloride (2) reacts with glycine (NH2CH2COOH) in the presence of sodium hydroxide (NaOH) to obtain a p-substituted benzoyl glycine compound or hippuric acid (3) in good yield. The substituted benzoyl glycine compound is washed with cold water, dried, and recrystallized from boiling water, results in a 90 % yield of hippuric acid (3). At one step, the hippuric acid (3) condenses with various substituted aromatic aldehydes (4a–e) in the presence of zirconium (Zr) and phosphorus (P) co-doped titanium dioxide (TiO2) nano photocatalyst and acetic anhydride to obtain one or more reaction mixtures, thereby taking the each reaction mixture in at least one conical flask. The aromatic aldehydes (4a–e) are selected from at least one of benzaldehydes, p-nitro benzaldehydes, m-nitro benzaldehydes, o-nitro benzaldehydes, and p-methoxy benzaldehydes. The zirconium (Zr) and phosphorus (P) co-doped titanium dioxide (TiO2) nano photocatalyst is prepared by a sol-gel method.

[0025] At one step, the each reaction mixture irradiates in a microwave oven at a power of at least 300 W and sonicating for a time period of at least 3 to 4 min. The reaction mixture is monitored by thin-layer chromatography (TLC). The reaction mixture is thoroughly mixed using a rotatory evaporator to prevent the evaporation of the acetic anhydride from the reaction mixture. At one step, the titanium dioxide (TiO2) nano photocatalyst filters and the each reaction mixture evaporates to obtain crude products, thereby recrystallizing the obtained crude products from hot benzene to obtain pure azlactones (5). The obtained crude products exhibit yellow or reddish-tinged crystals. The obtained azlactones are 2-Phenyl-4-(4-N,N-dimethylamino arylidene)-1,3- oxazol-5-one (5a), 2-Phenyl-4-(4-methoxy arylidene)-1,3-oxazol-5-one (5b), 2-Phenyl-4-(3-methoxy, 4-hydroxy arylidene)-1,3- oxazol-5-one (5c), 2-Phenyl-4-(3-nitro arylidene)-1,3-oxazol-5-one (5d), 2-Phenyl-4-(4-chloro arylidene)-1,3-oxazol-5-one (5e) are obtained in less time intervals with excellent yields.

[0026] Further, objects and advantages of the present invention will be apparent from a study of the following portion of the specification, the claims, and the attached drawings.
Detailed description of drawings:
[0027] The accompanying drawings, which are incorporated in and constitute a part of the specification, illustrate an embodiment of the invention, and, together with the description, explain the principles of the invention.

[0028] FIG. 1 illustrates a synthetic scheme depicting azlactones synthesis, in accordance to an exemplary embodiment of the invention.

[0029] FIGs. 2A-2E illustrate skeletal structures of all synthesized azlactone compounds (5a-e) by microwave-assisted synthesis, in accordance to an exemplary embodiment of the invention.

[0030] FIG. 3 illustrates a 13CNMR Spectrum of 4-(4- N, N- dimethyl amino benzylidene)-2- phenyl Oxazol-5(4H)-one (5a), in accordance to an exemplary embodiment of the invention.

[0031] FIG. 4 illustrates a 1HNMR spectrum of 4-(41- N, N- dimethyl amino benzylidene)-2- phenyl Oxazol-5(4H)-one (5a), in accordance to an exemplary embodiment of the invention.

[0032] FIG. 5 illustrates a FTIR Spectrum of 4-(4- N, N- dimethyl amino benzylidene)-2- phenyl Oxazol-5(4H)-one (5a), in accordance to an exemplary embodiment of the invention.

[0033] FIG. 6 illustrates a 1HNMR spectrum of 4-(41- methoxybenzylidene)-2- phenyl oxazol-5(4H)-one (5b), in accordance to an exemplary embodiment of the invention.

[0034] FIG. 7 illustrates a FTIR spectrum of 4-(41- methoxybenzylidene)-2- phenyl oxazol-5(4H)-one (5b), in accordance to an exemplary embodiment of the invention.

[0035] FIG. 8 illustrates a 13CNMR spectrum of 4-(41- methoxybenzylidene)-2- phenyl oxazol-5(4H)-one (5b), in accordance to an exemplary embodiment of the invention.

[0036] FIG. 9 illustrates a 1HNMR spectrum of 4-(41-chloro benzylidene)-2-phenyl oxazol-5(4H)-one(5e), in accordance to an exemplary embodiment of the invention.

[0037] FIG. 10 illustrates a flowchart of a method for synthesizing azlactones, in accordance to an exemplary embodiment of the invention.
Detailed invention disclosure:
[0038] Various embodiments of the present invention will be described in reference to the accompanying drawings. Wherever possible, same or similar reference numerals are used in the drawings and the description to refer to the same or like parts or steps.

[0039] The present disclosure has been made with a view towards solving the problem with the prior art described above, and it is an object of the present invention to provide a novel and efficient method for azlactones synthesis through microwave irradiation using zirconium (Zr) and phosphorus (P) co-doped titanium dioxide (TiO2) nano photocatalyst, thereby achieving efficient yields in significantly shorter time intervals.

[0040] Conventional synthesis of azlactones typically involves prolonged reaction times, elevated temperatures, and the use of hazardous reagents or solvents, resulting in increased energy consumption and potential environmental harm. Moreover, conventional catalysts may exhibit limited efficiency, leading to lower yields and undesired side reactions. These methods often lack selectivity, and the purification of the final product can be challenging, resulting in increased costs and reduced overall process efficiency. Additionally, the compatibility of these methods with various functional groups can be limited. The absence of green chemistry principles in existing approaches further hampers their sustainability and contribution to environmental preservation. Therefore, there is a pressing need for an improved method that addresses these drawbacks and offers a more efficient, selective, and environmentally friendly approach to azlactones synthesis.

[0041] According to one exemplary embodiment of the invention, FIG. 1 refers to a synthetic scheme depicting azlactones synthesis. The method that reduces reaction times from at least 1-2 hr to just 3-5 min, thereby offering a substantial improvement over conventional method. The method that utilizes a novel zirconium (Zr) and phosphorus (P) co-doped titanium dioxide (TiO2) nano photocatalyst, which achieves efficient yields at least 96 %, thereby ensuring high product purity and reducing the need for additional purification process. The method that adheres to green chemistry principles by minimizing the use of toxic reagents and reducing waste, thereby making the process safer and more sustainable.

[0042] In one embodiment herein, the azlactones synthesis is carried out in steps. At first, a mixture of at least 0.1 mole of substituted benzoic acid (1) in the presence of at least 30 mL of dichloromethane (DCM) is slowly added to at least 0.3 mole of thionyl chloride (SOCl2). In one embodiment herein, the substituted benzoic acid (1) may be selected from at least one of p-substituted benzoic acid, m-substituted benzoic acid, and o-substituted benzoic acid. Later, the reaction mixture is heated to reflux for a time period of at least 2 hr to obtain viscous acid chlorides (RCOCl) (2). The resulting viscous acid chlorides (2) are used without further purification.

[0043] Later, the acid chlorides (RCOCl) (2) are added to a well-stirred mixture of at least 0.1 mole of glycine (NH2CH2COOH) in at least 30 mL of 2N sodium hydroxide (NaOH) solution. Later, the reaction mixture is stirred vigorously for a time period of at least 1 hr. Later, the reaction mixture is poured into crushed ice and neutralized with concentrated hydrochloric acid (HCl) with stirring. Later, the obtained solid, i.e., p-substituted benzoyl glycine from various reactions, is washed with cold water, dried, and recrystallized from boiling water with at least 90 % yield to obtain hippuric acid (3).

[0044] Later, the obtained hippuric acid (3) is treated with various substituted aromatic aldehydes (4a–e) in the presence of zirconium (Zr) and phosphorus (P) co-doped TiO2 nano photocatalyst and acetic anhydride to obtain one or more reaction mixtures. In one embodiment therein, the aromatic aldehydes (4a-e) may be selected from at least one of benzaldehyde, p-nitrobenzaldehyde, m-nitrobenzaldehyde, o-nitrobenzaldehyde, and p-methoxybenzaldehyde. It is made sure that the photocatalyst is exposed to ultraviolet (UV) light for a time period of 30 min for activation before starting the reaction. Later, the each reaction mixture is taken into a glass with a cap and placed in a microwave oven for a time period of at least 3 to 4 min. The reaction progress is monitored by thin layer chromatography (TLC). The reaction mixture is thoroughly mixed using a rotatory evaporator to prevent the evaporation of the acetic anhydride from the reaction mixture.

[0045] In one embodiment herein, the novel photocatalyst employed in the reaction is a zirconium (Zr) and phosphorus (P) co-doped TiO2 nanoparticulate catalyst, which is synthesized through a sol-gel method. In the case of zirconium (Zr) and phosphorus (P) co-doped TiO2, the solution is typically prepared by mixing titanium isopropoxide (TIP), zirconium chloride (ZrCl4), and phosphoric acid (H3PO4) in an appropriate solvent, such as ethanol. The solution is then allowed to gel under controlled conditions, typically at room temperature and atmospheric pressure. The gel is then dried and calcined at a high temperature, typically around 500 °C, to obtain the desired zirconium (Zr) and phosphorus (P) co-doped TiO2 nano photocatalyst material. By incorporating both doped metal and non-metal into TiO2, the photocatalytic activity is enhanced through a reduction in the band gap and an increase in surface area.

[0046] Later, the each reaction mixture is irradiated in the microwave oven at a power of at least 300 W and sonicating for a time period of at least 3 to 4 min. The reaction mixture is extracted with at least 20 mL of cold methanol, and the TiO2 nano photocatalyst is filtered off. Later, the solvent is evaporated to obtain crude products. Further, the obtained crude products are crystallized from hot benzene to obtain pure azlactones. In one embodiment herein, the obtained azlactones are 2-(4-substituted phenyl)-4-(substituted arylidene)-1,3-oxazol-5-ones (5a–e). The obtained crude products exhibit yellow or reddish-tinged crystals. the obtained azlactones (5a-e) are 2-Phenyl-4-(4-N,N-dimethylamino arylidene)-1,3- oxazol-5-one (5a), 2-Phenyl-4-(4-methoxy arylidene)-1,3-oxazol-5-one (5b), 2-Phenyl-4-(3-methoxy, 4-hydroxy arylidene)-1,3- oxazol-5-one (5c), 2-Phenyl-4-(3-nitro arylidene)-1,3-oxazol-5-one (5d), 2-Phenyl-4-(4-chloro arylidene)-1,3-oxazol-5-one (5e) are obtained in less time intervals with excellent yields.

[0047] According to another exemplary embodiment of the invention, FIGs. 2A-2E refer to skeletal structures of all synthesized azlactone compounds (5a-e) by microwave-assisted synthesis. the obtained azlactones (5a-e) are 2-Phenyl-4-(4-N,N-dimethylamino arylidene)-1,3- oxazol-5-one (5a), 2-Phenyl-4-(4-methoxy arylidene)-1,3-oxazol-5-one (5b), 2-Phenyl-4-(3-methoxy, 4-hydroxy arylidene)-1,3- oxazol-5-one (5c), 2-Phenyl-4-(3-nitro arylidene)-1,3-oxazol-5-one (5d), 2-Phenyl-4-(4-chloro arylidene)-1,3-oxazol-5-one (5e) are obtained in less time intervals with excellent yields.

[0048] In one embodiment herein, the general procedure for the synthesis of 2-(4-substituted phenyl)-4-(substituted arylidene)-1,3-oxazol-5-ones (5a–e) by conventional synthesis. The mixture of at least 0.1 mole of substituted benzoic acid (1) in the presence of the at least 30 mL of dichloromethane (DCM) is slowly added to the at least 0.3 mol of thionyl chloride (SOCl2). and heated to reflux for at least 2 hr to obtain the viscous acid chlorides (2). The resulting viscous acid chlorides (2) are added to a well-stirred mixture of at least 0.1 mol least glycine in the at least 30 mL of 2N sodium hydroxide (NaOH) solution and stirred vigorously for at least 1 hr. The reaction mixture obtained is poured into crushed ice and neutralized with concentrated hydrochloric acid with stirring. The obtained solid, i.e., p-substituted benzoyl glycine of various reactions (3), is washed with cold water, dried, and recrystallized from boiling water with at least 90 % yield. The compound 3(Benzoyl glycine) thus obtained is treated with the different substituted aromatic aldehydes (0.01 mol) (4a–e) containing various electron-donating and electron-withdrawing groups.
[0049] The at least 0.01 mol of Zr/P co-doped TiO2 is used as a nano photocatalyst in the presence of at least 0.03 mol of high-grade acetic anhydride, thereby enhancing the rate of reaction. The entire reaction mixture is initially heated on a hot plate at the temperature of at least 110 °C for at least 20 min and then in the water bath for at least 60 – 80 min, with occasional stirring and monitored by the Thin Layer Chromatography (TLC). The TiO2 nano photocatalyst was filtered off from the warm reaction mixture. On cooling, the at least 10 mL of ethanol is added slowly to the reaction mixture and left for at least 4–5 hr. The crystalline product obtained is filtered under suction, washed with ice-cold ethanol and boiling water, and then dried. The crude oxazolones obtained (5a–e) are recrystallized from either chloroform or hot benzene in good yields. The compounds and their yields of 5a,5b,5c,5d,5e are 93 %, 91 %, 92 %, 90 %, 85 % respectively, in different time intervals 60 min, 65 min, 70 min, 75 min, 80 min as shown in the Table 1.

[0050] In one embodiment herein, the general procedure for the synthesis of 2-(4-substituted phenyl)-4-(substituted arylidene)-1, 3-oxazol-5-ones (5a–e) by microwave irradiation. A mixture of substituted benzoic acid (1) (0.1 mol) in DCM (30 mL) is added slowly to thionyl chloride (0.3 mol) and heated to reflux for 2 hr. The resulting viscous acid chlorides (2) are added to a well-stirred mixture of glycine (0.1 mol) in NaOH (30 mL, 2N) and stirred vigorously for 1 hr. The reaction mixture obtained is poured into crushed ice and neutralized with concentrated hydrochloric acid with stirring. The obtained solid, i.e., p-substituted benzoyl glycine of various reactions (3), i.e.; the Hippuric acid is prepared by a conventional method.

[0051] The hippuric acid (compound 3) is treated with various aromatic aldehydes (4a–e) in the presence of nano photo catalyst Zr/P co-doped TiO2 and acetic anhydride. The Substances are taken into the conical flask and it is placed in the microwave oven, the microwave irradiation on the substances for at least 3 to 4 min the results are shown in table-(1) and frequently monitored by TLC. The compounds are extracted with cold methanol (20 mL) The TiO2 nano photo catalyst was filtered off and the solvent was evaporated to yield the crude products, which were re-crystallized from hot benzene. Many of the title compounds showed yellow/ reddish-tinged crystals. The yields obtained for the target molecules 5a, 5b, 5c, 5d, 5e are 96 %, 94 %, 95 %, 94 %, 89 % respectively, in different time intervals 3 min, 3.2 min, 3.5 min, 3.7 min, 4.0 min as shown in the Table 1.

[0052] Table 1:
Compound Conventional Synthesis Microwave synthesis
Yield (%) Time(min) Yield (%) Time(min)
5a 93 60 96 3.0
5b 91 65 94 3.2
5c 92 70 95 3.5
5d 90 75 94 3.7
5e 85 80 89 3.9

[0053] In one embodiment herein, the characterization data of all synthesized compounds of the obtained azlactones (5a-e) by the microwave-assisted synthesis as shown in the FIGs 2A-2E. The obtained azlactones (5a-e) are 2-Phenyl-4-(4-N,N-dimethylamino arylidene)-1,3- oxazol-5-one (5a), 2-Phenyl-4-(4-methoxy arylidene)-1,3-oxazol-5-one (5b), 2-Phenyl-4-(3-methoxy, 4-hydroxy arylidene)-1,3- oxazol-5-one (5c), 2-Phenyl-4-(3-nitro arylidene)-1,3-oxazol-5-one (5d), 2-Phenyl-4-(4-chloro arylidene)-1,3-oxazol-5-one (5e) are obtained in less time intervals with excellent yields.

[0054] In one embodiment herein, the compound 5a is 2-Phenyl-4-(4-N, N-dimethylamino arylidene)-1,3-oxazol-5-one (5a). The skeletal structure of the 2-Phenyl-4-(4-N, N-dimethylamino arylidene)-1,3-oxazol-5-one (5a) is shown the FIG 2A. The appearances of the 2-Phenyl-4-(4-N, N-dimethylamino arylidene)-1,3-oxazol-5-one (5a) is in reddish crystals. The melting point (m.p) of the compound 5a at a temperature varies between 209°C and 211°C. The IR spectrum of the compound 5a peaks at 1446, 1646, and 1762 cm?¹. The 1 H NMR (90 MHz, CDCl3, d, ppm): 3.10 (s, NMe2, 6H), 6.69-6.71 (m, Ar-H, 2H), 7.39 (s, Ar-CH, 1H), 7.49–7.68 (m, Ar-H, 2H), 8.10–8.15 (m, Ar-H, 5H).13C NMR (22.5 MHz, CDCl3, d, ppm): 39.9, 128.8, 132.1, 160.6, 169.2, Anal. Cald. for C18H16N2O2.

[0055] In one embodiment herein, the compound 5b is 2-Phenyl-4-(4-methoxy arylidene)-1,3-oxazol-5-one (5b). The skeletal structure of the 2-Phenyl-4-(4-methoxy arylidene)-1,3-oxazol-5-one (5b) is shown the FIG 2B. The appearances of the 2-Phenyl-4-(4-methoxy arylidene)-1,3-oxazol-5-one (5b) is in yellow crystals. The melting point (m.p) of the compound 5b at a temperature varies between 161°C and 162°C. The IR spectrum of the compound 5c Peaks at 1448, 1652, and 1768 cm?¹. The 1 H NMR (90 MHz, CDCl3, d, ppm): 3.87 (s, 3H, OCH3), 7.21 (s, 1H, Ar-H), 7.19–7.24 (m, 4H, Ar-H),7.79–7.89 (m, 5H),13C NMR (22.5 MHz, CDCl3, d, ppm): 55.5, 128.7. 131.9, 162.6, 167.7, Anal. Cald. for C17H13NO3.

[0056] In one embodiment herein, the compound 5C is 2-Phenyl-4-(3-methoxy, 4-hydroxy arylidene)-1,3- oxazol-5-one (5c). The skeletal structure of the 2-Phenyl-4-(3-methoxy, 4-hydroxy arylidene)-1,3- oxazol-5-one (5c) is shown the FIG 2C. The appearances of the 2-Phenyl-4-(3-methoxy, 4-hydroxy arylidene)-1,3- oxazol-5-one (5c) is in yellow crystals. The melting point (m.p) of the compound 5c at a temperature varies between 211°C and 212°C. The IR spectrum of the compound 5c Peaks at 1452, 1650, and 1755 cm?¹. The 1 H NMR (90 MHz, CDCl3, d, ppm): 3.86(s, 3H, OCH3), 7.12 (s, 1H, Ar-CH), 7.11–7.18 (m, 3H, Ar-H),7.39–7.59 (m, 5H, Ar-H), 8.4 (s, 1H, OH),13C NMR (22.5 MHz, CDCl3, d, ppm): 55.1, 127.5, 131.9, 161.8, 168.3; Anal.Cald. for C17H13NO4.

[0057] In one embodiment herein, the compound 5d is 2-Phenyl-4-(3-nitro arylidene)-1,3-oxazol-5-one (5d). The skeletal structure of the 2-Phenyl-4-(3-nitro arylidene)-1,3-oxazol-5-one (5d) is shown the FIG 2D. The appearances of the 2-Phenyl-4-(3-methoxy, 4-hydroxy arylidene)-1,3- oxazol-5-one (5d) is in yellow crystals. The melting point (m.p) of the compound 5c at a temperature varies between 188°C and 190°C. The IR spectrum of the compound 5d Peaks at 1530, 1657, and 1768 cm?¹. The 1 H NMR (90 MHz, CDCl3, d, ppm): 7.19 (s, 1H, Ar-CH), 7.49–7.69 (m, 4H, Ar-H),8.11–8.29 (m, 3H, Ar-H), 8.39 (d, J = 8.2 Hz, 1H, Ar-H), 9.18 (s, 1H).13C NMR (22.5 MHz, CDCl3, d, ppm): 131.2, 139.3, 164.5, 167.4; Anal. Cald. for C16H10N2O4.

[0058] In one embodiment herein, the compound 5e is 2-Phenyl-4-(4-chloro arylidene)-1,3-oxazol-5-one (5e). The skeletal structure of the 2-Phenyl-4-(4-chloro arylidene)-1,3-oxazol-5-one (5e) is shown the FIG 2E. The appearances of the 2-Phenyl-4-(4-chloro arylidene)-1,3-oxazol-5-one (5e) is in light yellow crystals. The melting point (m.p) of the compound 5e at a temperature varies between 174°C and 175°C. The IR spectrum of the compound 5e Peaks at 1450, 1654, and 1766 cm?¹. The 1 H NMR (90 MHz, CDCl3, ?max, d, ppm): 7.29 (s, Ar-H, 1H), 7.11–7.28 (m, 6H, ArH),8.11–8.17(m, 3H, Ar-H); 13C NMR (22.5 MHz, CDCl3, d, ppm): 131.5, 134.9, 165.2, 166.8; Anal. Cald. for C16H10NO2Cl.

[0059] According to another exemplary embodiment of the invention, FIG. 3 refers to a 13CNMR Spectrum of 4-(4- N,N- dimethyl amino benzylidene)-2- phenyl Oxazol-5(4H)-one (5a). A Nuclear Magnetic Resonance (NMR) spectroscopy is a technique used to identify the structure of molecules. This graph is an example of the Nuclear Magnetic Resonance (NMR) spectroscopy spectrum. The horizontal axis represents the chemical shift (d) in parts per million (ppm), while the vertical axis represents the intensity of the NMR signal. The chemical shift (d) indicates the environment of the nuclei being observed (usually hydrogen-1 or carbon-13). The peaks in the spectrum correspond to different types of hydrogen or carbon atoms in the molecule. The height (intensity) of each peak indicates the number of nuclei contributing to that signal.

[0060] In one embodiment herein, the 13C NMR (22.5 MHz, CDCl3, d, ppm): 39.9, 128.8, 132.1, 160.6, 169.2, Anal. Cald. for C18H16N2O2. The provided ¹³C NMR data offers valuable insights into the molecule's carbon framework. The carbon atoms in different chemical environments resonate at distinct frequencies in NMR spectroscopy. These frequencies are reflected as chemical shift (d) values in ppm. These values are compared with known ranges for various carbon types. The Aliphatic (alkanes) ranges between 0-60 ppm, Alkenes ranges between 100-140 ppm, Aromatic ranges between 110-160 ppm, Carboxylic acid ranges between 165 and 185 ppm and Carbonyl (ketones, aldehydes, amides) ranges between 160 and200 ppm.

[0061] The provided ¹³C NMR data indicates Carbon-13 NMR spectroscopy performed at 22.5 MHz frequency in chloroform (CDCl3) solvent. The d values are similar to the proton NMR, these are chemical shift values reported in ppm for different carbon atoms in the molecule. The d 39.9, 128.8, 132.1, 160.6, 169.2 are peaks correspond to various carbon atoms in the molecule.

[0062] The d 39.9 value falls within the aliphatic range (0-60 ppm), suggesting a possible methyl (CH3) or methylene (CH22) group in a relatively non-polar environment. The d 128.8 ppm and d 132.1 ppm values fall within the aromatic range (110-160 ppm), indicating the presence of aromatic carbons (sp² hybridized) in a ring structure. The slight difference in chemical shifts suggests these carbons might be in slightly different environments within the aromatic ring system. The d 160.6 ppm This value lies at the upper end of the aromatic range (110-160 ppm) and could also be indicative of a carbonyl carbon (C=O) in a ketone or amide group. The d 169.2 ppm value falls within the carboxylic acid range (165-185 ppm), strongly suggesting the presence of a carbonyl carbon (C=O) in a carboxylic acid group (COOH).

[0063] According to another exemplary embodiment of the invention, FIG. 4 refers to a 1HNMR spectrum of 4-(41- N, N- dimethyl amino benzylidene)-2- phenyl Oxazol-5(4H)-one (5a). The 1 H NMR (90 MHz, CDCl3, d, ppm): 3.10 (s, NMe2, 6H), 6.69-6.71 (m, Ar-H, 2H), 7.39 (s, Ar-CH, 1H), 7.49–7.68 (m, Ar-H, 2H), 8.10–8.15 (m, Ar-H, 5H). The chemical shift (d) values indicate the position of proton resonances in ppm relative to a reference standard. The CDCl3 (Chloroform) is a common solvent used in NMR spectroscopy. This graph is a proton NMR (Nuclear Magnetic Resonance) spectrum for 5a. The horizontal axis represents the chemical shift (d) in parts per million (ppm), which indicates the environment of the hydrogen nuclei (protons). The chemical shift values provide information about the electronic environment surrounding the protons. The vertical axis represents the absorption of energy, which corresponds to the number of protons contributing to each signal.

[0064] In one embodiment herein, d 3.10 (s, NMe2, 6H), a singlet (s) peak signifies all protons in this environment experience the same magnetic field and resonate at the same frequency. An integration value (6H) indicates six equivalent protons. A NMe2 assignment suggests these protons are attached to a Dimethylamine (CH3)2N group.

[0065] In one embodiment herein, d 6.69-6.71 (m, Ar-H, 2H), a multiplet (m) peak implies slightly different chemical environments for these protons, leading to a broader peak. The integration value (2H) suggests two protons. Ar-H assignment suggests these protons are on the aromatic ring.

[0066] In one embodiment herein, d 7.39 (s, Ar-CH, 1H), the singlet (s) peak signifies a single proton in a unique environment. The integration value (1H) confirms one proton. The Ar-CH assignment suggests this proton is a methine (CH) on the aromatic ring.

[0067] In one embodiment herein, d 8.10–8.15 (m, Ar-H, 5H), the multiplet (m) peak for five protons in similar aromatic environments. The integration value (5H) confirms five protons. The Ar-H assignment suggests these protons are on the aromatic ring.

[0068] In one embodiment herein, the ¹H NMR data confirms the presence of a Dimethylamine group (N(CH3)2) and several aromatic protons. The molecular formula (C18H16N2O2) corroborates the presence of 18 carbons, which aligns with the complex aromatic structure suggested by the NMR data. The two nitrogens match the dimethylamine group, and the 2 Oxygens likely correspond to the carbonyl group (C=O) and a hydroxyl group (OH) from the carboxylic acid (COOH).

[0069] According to another exemplary embodiment of the invention, FIG. 5 refers to a FTIR Spectrum of 4-(4- N, N- dimethyl amino benzylidene)-2- phenyl Oxazol-5(4H)-one (5a). In one embodiment herein, IR (KBr, ?max, cm-1): 1446, 1646, 1762. The IR spectrum of the compound 5a peaks at 1446, 1646, and 1762 cm?¹. The Infrared (IR) spectrum of the molecule is obtained using a Potassium Bromide (KBr) pellet technique. The sample is often mixed with KBr powder and pressed into a pellet for IR analysis. KBr is transparent in the IR region and doesn't interfere with the sample's spectrum. The ?max (cm?¹) notation indicates the wavenumbers (cm?¹) of the strongest absorption peaks in the spectrum.

[0070] This graph represents mass spectrum of the 5a. The x-axis shows the wavenumbers in cm^-1. The wavenumbers are related to the frequency of light and are used in infrared (IR) spectroscopy. The y-axis shows the transmittance. The transmittance is a measure of how much light passes through a sample. A high transmittance indicates that most of the light is passing through the sample, while a low transmittance indicates that most of the light is being absorbed by the sample.

[0071] The 1446 cm?¹ peak falls within the range for aromatic C-C stretching vibrations (typically 1400-1600 cm?¹). The presence of multiple aromatic rings in the molecule suggested by NMR data. The 1646 cm?¹ peak correspond to the Aromatic C=C stretching (along with C-C stretching) in some aromatic compounds (around 1600-1690 cm?¹). The presence of aromatic rings is suggested by NMR data is strongly supported by this peak. The 1762 cm?¹ peak falls within the range for carbonyl (C=O) stretching vibrations (typically 1700-1850 cm?¹). The presence of a carboxylic acid group suggested by NMR data is strongly supported by this peak.

[0072] According to another exemplary embodiment of the invention, FIG. 6 refers to a 1HNMR spectrum of 4-(41- methoxybenzylidene)-2- phenyl oxazol-5(4H)-one (5b). 1 H NMR (90 MHz, CDCl3, d, ppm): 3.87 (s, 3H, OCH3), 7.21 (s, 1H, Ar-H), 7.19–7.24 (m, 4H, Ar-H),7.79–7.89 (m, 5H). Different ¹H nuclei experience slightly different magnetic fields due to their surroundings, leading to resonance at distinct frequencies. These frequencies are converted into chemical shift (d) values reported in ppm relative to a reference standard (usually tetramethylsilane, TMS). The CDCl3 (Chloroform) is a common solvent used in NMR spectroscopy due to its good solubility for many organic compounds and its lack of interfering peaks in the ¹H NMR spectrum.

[0073] This graph is a proton NMR (Nuclear Magnetic Resonance) spectrum for 5b. The horizontal axis represents the chemical shift (d) in parts per million (ppm), which indicates the environment of the hydrogen nuclei (protons). The chemical shift values provide information about the electronic environment surrounding the protons. The vertical axis represents the intensity or absorption of energy, which corresponds to the number of protons contributing to each signal.

[0074] In one embodiment herein, d 3.87 (s, 3H, OCH3) is one of the peaks, the chemical shift (d) 3.87 ppm falls within the typical range for methoxy (OCH3) protons (around 3.1-4.0 ppm). The singlet (s) peak indicates all three protons in the methoxy group experience the same magnetic field and resonate at a single frequency. The integration value of 3 signifies there are three equivalent protons contributing to this peak. This peak confirms the presence of a methoxy group (-OCH3) bonded to an aromatic ring (Ar-OCH3).

[0075] In one embodiment herein, d 7.21 (s, 1H, Ar-H) is one of the peaks, the chemical shift (d) 7.21 ppm falls within the aromatic range (typically 6.5-8.5 ppm) for protons on a relatively electron-rich aromatic ring. The singlet (s) peak suggests a single proton in a unique electronic environment within the aromatic system. The integration value of 1 confirms one proton contributes to this peak. This peak indicates a single aromatic proton (Ar-H) on the ring.

[0076] In one embodiment herein, d 7.19–7.24 (m, 4H, Ar-H) is one of the peaks, the chemical shift (d) ranges between 7.19-7.24 ppm falls within the aromatic range. The multiplet (m) peak signifies slightly different chemical environments for these four protons, leading to a broader peak. The integration value of 4 suggests four equivalent protons contribute to this multiplet. These peaks likely correspond to four aromatic protons (Ar-H) on the same or a similar aromatic ring system.

[0077] In one embodiment herein, 7.79–7.89 (m, 5H) is one of the peaks, this multiplet (m) between 7.79 and 7.89 ppm signifies multiple overlapping peaks. The integration value of 5H suggests there are five protons contributing to these peaks. The absence of a specific designation suggests these protons might not be aromatic. This could represent another aromatic ring system with a slightly different chemical environment or protons on aliphatic carbons (carbons not in an aromatic ring).

[0078] According to another exemplary embodiment of the invention, FIG. 7 refers to a FTIR spectrum of 4-(41- methoxybenzylidene)-2- phenyl oxazol-5(4H)-one (5b). In one embodiment herein, IR (KBr, ?max, cm-1): 1448, 1652, 1768. The IR spectrum of the compound 5b peaks at 1448, 1652, and 1768 cm?¹. The IR indicates the infrared spectrum. R spectroscopy analyzes how a molecule absorbs specific frequencies of infrared radiation. The KBr refers to potassium bromide, a common material used to prepare a solid sample for IR analysis. The sample is mixed with KBr and pressed into a pellet. ?max represents the wavenumbers (cm?¹) of the strongest absorption peaks in the spectrum. The organic molecules vibrate at specific frequencies when exposed to IR radiation. Different functional groups have characteristic vibrational frequencies. By analyzing the peak positions (wavenumbers) in the IR spectrum, we can identify the functional groups present in the molecule.

[0079] This graph represents mass spectrum of the 5b. The x-axis shows the wavenumbers in cm^-1. The wavenumbers are related to the frequency of light and are used in infrared (IR) spectroscopy. The y-axis shows the transmittance. The transmittance is a measure of how much light passes through a sample. A high transmittance indicates that most of the light is passing through the sample, while a low transmittance indicates that most of the light is being absorbed by the sample.

[0080] In one embodiment herein, the 1448 cm?¹ peak can be attributed to bending vibrations of C-H bonds in alkanes (hydrocarbons with only single bonds between carbon atoms). It can also indicate the presence of aromatic rings. The 1652 cm?¹ peak likely corresponds to the carbonyl (C=O) stretching vibration. The carbonyl group is present in various functional groups, including ketones, aldehydes, carboxylic acids, amides, and esters. To identify the specific carbonyl-containing group, additional information like the ¹H NMR data or the chemical properties of the molecule would be helpful. The 1768 cm?¹ peak is less common and could be due to several possibilities. It might be indicative of a strong carbonyl stretching vibration in a conjugated system (where double bonds are next to each other) or a carboxylic acid dimer (two carboxylic acids linked together by hydrogen bonding). The IR spectrum suggests the molecule likely contains C-H bonds (alkanes or aromatics), a carbonyl group (ketone, aldehyde, carboxylic acid, amide, or ester), and possibly a conjugated system or a carboxylic acid dimer.

[0081] According to another exemplary embodiment of the invention, FIG. 8 refers to a 13CNMR spectrum of 4-(41- methoxybenzylidene)-2- phenyl oxazol-5(4H)-one (5b). 13C NMR (22.5 MHz, CDCl3, d, ppm): 55.5, 128.7. 131.9, 162.6, 167.7, Anal. Cald. for C17H13NO3. The provided ¹³C NMR data offers valuable insights into the molecule's carbon framework. The 22.5 MHz refers to the operating frequency of the NMR spectrometer used for the ¹³C NMR analysis. The CDCl3 (deuterated chloroform) is the solvent used for the analysis. The d (ppm) indicates chemical shift, measured in parts per million (ppm), which represents the position of a peak in the ¹³C NMR spectrum. The chemical shift is influenced by the electronic environment surrounding each carbon atom in the molecule. This graph is an example of the Nuclear Magnetic Resonance (NMR) spectroscopy spectrum. The horizontal axis represents the chemical shift (d) in parts per million (ppm), while the vertical axis represents the intensity of the NMR signal.

[0082] In one embodiment herein, the 55.5 ppm peak suggests a single carbon atom in a specific electronic environment. The chemical shift value (around 50-60 ppm) is typical for a methoxy carbon (OCH3) group. The 128.7 ppm and 131.9 ppm are two separate peaks likely correspond to carbon atoms in aromatic rings. Aromatic carbons typically resonate in the 120-140 ppm range. The presence of two distinct peaks suggests these carbons are not chemically equivalent, meaning they have slightly different electronic environments within the aromatic system. The 162.6 ppm and 167.7 ppm are two separate peaks at higher chemical shift values (around 160-180 ppm) are indicative of carbonyl carbons (C=O). The presence of two distinct carbonyl carbons suggests the molecule has two different carbonyl-containing functional groups. The Anal. Cald. for C17H13NO3 refers to elemental analysis data. The calculated values (Calcd.) are based on the proposed formula C17H13NO3.

[0083] In one embodiment herein, the one methoxy group (OCH3) confirmed by the ¹³C NMR peak at 55.5 ppm. The aromatic carbons indicated by the peaks at 128.7 ppm and 131.9 ppm. The Two distinct carbonyl groups based on the peaks at 162.6 ppm and 167.7 ppm. The formula C17H13NO3 is consistent with the observed peaks and the number of carbons, hydrogens, nitrogen, and oxygens.

[0084] According to another exemplary embodiment of the invention, FIG. 9 refers a 1HNMR spectrum of 4-(41-chloro benzylidene)-2-phenyl oxazol-5(4H)-one(5e). This graph is the proton NMR (Nuclear Magnetic Resonance) spectrum for 5e. The horizontal axis represents the chemical shift (d) in parts per million (ppm), which indicates the environment of the hydrogen nuclei (protons). The vertical axis represents the intensity or absorption of energy, which corresponds to the number of protons contributing to each signal. 1 H NMR (90 MHz, CDCl3, ?max, d, ppm): 7.29 (s, Ar-H, 1H), 7.11–7.28 (m, 6H, ArH),8.11–8.17(m, 3H, Ar-H). the 7.29 (s, 1H, Ar-H) peak appears at 7.29 ppm as a singlet (s), signifying a single, sharp peak with an integration of 1H (assumed but not explicitly mentioned). The "Ar-H" designation suggests it's a proton on an aromatic ring (Ar). This indicates a single aromatic proton in a specific chemical environment within the molecule. The 7.11–7.28 (m, 6H, Ar-H) suggests overlapping peaks as a multiplet (m) spread between 7.11 and 7.28 ppm.

[0085] The integration value of 6H (assumed but not explicitly mentioned) implies there are six protons contributing to these peaks. The "Ar-H" designation again indicates these are aromatic protons. This likely corresponds to a set of six aromatic protons in close proximity on the molecule's aromatic ring system. The 8.11–8.17 (m, 3H, Ar-H) signifies multiple overlapping peaks as the multiplet (m) between 8.11 and 8.17 ppm. The integration value of 3H (assumed but not explicitly mentioned) suggests there are three protons contributing to these peaks. The "Ar-H" designation suggests these are aromatic protons. This could represent another aromatic ring system with a slightly different chemical environment or protons on aromatic carbons experiencing a different electronic influence.

[0086] According to another exemplary embodiment of the invention, FIG. 10 refers to a flowchart 1000 of a method for synthesizing azlactones. At one step 1002, a p-substituted benzoic acid (1) is reacted with thionyl chloride (SOCl2) in the presence of dichloromethane (DCM) to obtain a viscous acid chloride (RCOCl) (2). The substituted benzoic acid is selected from at least one of p-substituted benzoic acid, m-substituted benzoic acid, and o-substituted benzoic acid. At step 1004, the viscous acid chloride (2) reacts with glycine (NH2CH2COOH) in the presence of sodium hydroxide (NaOH) to obtain a p-substituted benzoyl glycine compound or hippuric acid (3) in good yield. The substituted benzoyl glycine compound is washed with cold water, dried, and recrystallized from boiling water, results in a 90 % yield of hippuric acid (3). At step 1006, the hippuric acid (3) condenses with various substituted aromatic aldehydes (4a–e) in the presence of zirconium (Zr) and phosphorus (P) co-doped titanium dioxide (TiO2) nano photocatalyst and acetic anhydride to obtain one or more reaction mixtures, thereby taking the each reaction mixture in at least one conical flask. The aromatic aldehydes (4a–e) are selected from at least one of benzaldehydes, p-nitrobenzaldehydes, m-nitrobenzaldehydes, o-nitrobenzaldehydes, and p-methoxybenzaldehydes. The zirconium (Zr) and phosphorus (P) co-doped titanium dioxide (TiO2) nano photocatalyst is prepared by a sol-gel method.

[0087] At step 1008, the each reaction mixture irradiates in a microwave oven at a power of at least 300 W and sonicating for a time period of at least 3 to 4 min. The reaction mixture is monitored by thin-layer chromatography (TLC). The reaction mixture is thoroughly mixed using a rotatory evaporator to prevent the evaporation of the acetic anhydride from the reaction mixture. At step 1010, the titanium dioxide (TiO2) nano photocatalyst filters and the each reaction mixture evaporates to obtain crude products, thereby recrystallizing the obtained crude products from hot benzene to obtain pure azlactones (5). The obtained crude products exhibit yellow or reddish-tinged crystals. The obtained azlactones are 2-Phenyl-4-(4-N,N-dimethylamino arylidene)-1,3- oxazol-5-one (5a), 2-Phenyl-4-(4-methoxy arylidene)-1,3-oxazol-5-one (5b), 2-Phenyl-4-(3-methoxy, 4-hydroxy arylidene)-1,3- oxazol-5-one (5c), 2-Phenyl-4-(3-nitro arylidene)-1,3-oxazol-5-one (5d), 2-Phenyl-4-(4-chloro arylidene)-1,3-oxazol-5-one (5e) are obtained in less time intervals with excellent yields.

[0088] Numerous advantages of the present disclosure may be apparent from the discussion above. In accordance with the present disclosure synthesis of azlactones through microwave irradiation using zirconium-phosphorus co-doped titanium oxide nano photocatalyst is disclosed. The proposed invention provides a method that reduces reaction times from at least 1-2 hr to just 3-5 min, thereby offering a substantial improvement over conventional method. The method utilizes a novel zirconium (Zr) and phosphorus (P) co-doped titanium dioxide (TiO2) nano photocatalyst, which achieves efficient yields at least 96 %, thereby ensuring high product purity and reducing the need for additional purification process.

[0089] The proposed invention provides the method that utilizes a novel zirconium (Zr) and phosphorus (P) co-doped titanium dioxide (TiO2) nano photocatalyst, which offers increased catalytic activity due to its larger surface area and reduced band gap energy, thereby providing more efficient reactions with higher specificity and fewer side products. The method utilizes the novel zirconium (Zr) and phosphorus (P) co-doped titanium dioxide (TiO2) nano photocatalyst, which can be reused multiple times without losing activity, thereby making the process more sustainable and cost-effective. The method adheres to green chemistry principles by minimizing the use of toxic reagents and reducing waste, thereby making the process safer and more sustainable.

[0090] It will readily be apparent that numerous modifications and alterations can be made to the processes described in the foregoing examples without departing from the principles underlying the invention, and all such modifications and alterations are intended to be embraced by this application.
, Claims:CLAIMS:
I/We Claim:
1. A method for synthesizing azlactones through microwave irradiation, comprising:
reacting a p-substituted benzoic acid (1) in the presence of dichloromethane (DCM) with thionyl chloride (SOCl2) to obtain a viscous acid chloride (RCOCl) (2);

reacting the viscous acid chloride (2) with glycine (NH2CH2COOH) in the presence of sodium hydroxide (NaOH) to obtain a p-substituted benzoyl glycine compound or hippuric acid (3) in good yield;

condensing the hippuric acid (3) with various substituted aromatic aldehydes (4a–e) in the presence of zirconium (Zr) and phosphorus (P) co-doped titanium dioxide (TiO2) nano photocatalyst and acetic anhydride to obtain one or more reaction mixtures, thereby taking the each reaction mixture in at least one conical flask;
irradiating the each reaction mixture in a microwave oven at a power of at least 300 W and sonicating for a time period of at least 3 to 4 min; and
filtering the titanium dioxide (TiO2) nano photocatalyst and evaporating the each reaction mixture to obtain crude products, thereby recrystallizing the obtained crude products from hot benzene to obtain pure azlactones (5).

2. The method as claimed in claim 1, wherein the obtained azlactones (5a-e) are 2-Phenyl-4-(4-N,N-dimethylamino arylidene)-1,3- oxazol-5-one (5a), 2-Phenyl-4-(4-methoxy arylidene)-1,3-oxazol-5-one (5b), 2-Phenyl-4-(3-methoxy, 4-hydroxy arylidene)-1,3- oxazol-5-one (5c), 2-Phenyl-4-(3-nitro arylidene)-1,3-oxazol-5-one (5d), 2-Phenyl-4-(4-chloro arylidene)-1,3-oxazol-5-one (5e) are obtained in less time intervals with excellent yields.
3. The method as claimed in claim 1, wherein the substituted benzoic acid is selected from at least one of p-substituted benzoic acid, m-substituted benzoic acid, and o-substituted benzoic acid.
4. The method as claimed in claim 1, wherein the aromatic aldehydes (4a–e) are selected from at least one of benzaldehydes, p-nitrobenzaldehydes, m-nitrobenzaldehydes, o-nitrobenzaldehydes, and p-methoxybenzaldehydes.
5. The method as claimed in claim 1, wherein the substituted benzoyl glycine compound is washed with cold water, dried, and recrystallized from boiling water, resulting in a 90 % yield of hippuric acid (3).
6. The method as claimed in claim 1, wherein the zirconium (Zr) and phosphorus (P) co-doped titanium dioxide (TiO2) nano photocatalyst is prepared by a sol-gel method.
7. The method as claimed in claim 1, wherein the zirconium (Zr) and phosphorus (P) co-doped titanium dioxide (TiO2) nano photocatalyst is exposed to ultraviolet UV light for at least 30 min for activation before performing the method.
8. The method as claimed in claim 1, wherein the reaction mixture is monitored by thin-layer chromatography (TLC).
9. The method as claimed in claim 1, wherein the reaction mixture is thoroughly mixed using a rotatory evaporator to prevent the evaporation of the acetic anhydride from the reaction mixture.
10. The method as claimed in claim 1, wherein the obtained crude products exhibit yellow or reddish-tinged crystals.