DESC:FORM 2

THE PATENTS ACT, 1970
[39 of 1970]

&
THE PATENTS RULES, 2003

COMPLETE SPECIFICATION

(Section 10; Rule 13)

A PROCESS FOR SYNTHESIS OF Z-9-HEXADECENOL

Barrix Agro Sciences Private Limited

1A-C Block, 2nd Floor, Kushal Garden Arcade,
2nd Phase, Peenya, Bangalore - 560058
India

An Indian Company

The following Specification particularly describes the invention and the manner in which it is to be performed
FIELD OF INVENTION
This present invention relates synthetically preparing chemicals of interest. More particularly it relates to process for preparation of Z-9-hexadecenol.

BACKGROUND OF INVENTION
Insect infestation of crops is a primary cause of crop loss throughout the world. A wide variety of chemical pesticides have been used for the purpose of pest/insect control in the fields. However, most of these chemicals are not safe for person spraying the pesticides, consumers of the harvest, while at the same time the pesticides also pollute the soil in the field and contaminate the water. Therefore, taking into consideration the environmental concerns as well as consumer safety the scientists have developed alternative biological control agents, which are environment friendly and effective in getting rid of the pests. One such example is use of sexual pheromone as biological control agents. The pheromones are non-toxic, secreted by insect of one gender to attract other gender of the same species even in an extremely small amount.

Z-9-hexadecenol is a useful compound as an intermediate for the synthesis of Z-9-hexadecenal, which is a known sexual pheromone compound of Helicoverpa zea, Heliothis punctigera, Plutella xylostella, Helicoverpa armigera and Z-9-hexadecenyl acetate, which is known sexual pheromone compound for Homona coffearia. The Z-9-hexadecenal and Z-9-hexadecenyl acetate provide a promising means for the extermination of these insects in the field. The said pheromones can of course be prepared by a chemical method of synthesis. However, economically advantageous methods for the synthetic preparation of the Z-9-hexadecenol have not yet been proposed.

In view of the foregoing, the pest management and control systems earnestly need an economical process for the preparation of Z-9-hexadecenol which could use readily available and inexpensive starting materials and has high yield.

The above mentioned shortcomings and problems are addressed through the below specifications.

SUMMARY OF THE INVENTION

The present disclosure provides a process for preparation of Z-9-hexadecenol.

In one aspect of the present invention, the process for preparation of Z-9-hexadecenol includes (1) reacting one of hydroxides of sodium and carbonates of sodium and one of hydroxides of potassium and carbonates of potassium, with aleuritic acid to form respectively, sodium aleuritate and potassium aleuritate, where the reaction is allowed to occur for a duration of 1 hour at temperature ranging from 10 to 15 °C; (2) oxidizing the one of sodium aleuritate and potassium aleuritate with sodium periodate, wherein the oxidization is performed at temperature of 15 °C; (3) hydrolysing the oxidized one of sodium aleuritate and potassium aleuritate with first set of one or more mineral acids to form 9-oxononanoic acid, wherein the first set of one or more mineral acids are selected from a group consisting of dilute HCl and dilute H2SO4; (4) reacting primary halides of heptane with triphenylphosphine in presence of first set of one or more organic solvents to form phosphonium salt, wherein the first set of one or more organic solvents are selected from a group consisting of toluene, benzene, tetrahydrofuran (THF), dimethylformamide (DMF), acetonitrile and dimethyl sulfoxide (DMSO), wherein the reaction is carried out at temperature maintained between 50 to 120 °C, more preferably between 82 to 86 °C, for a duration ranging between 12 to 24 hours, more preferably between 16 to 20 hours; (5) reacting the phosphonium salt with the 9-oxononanoic acid, in the presence of one or more bases and a second set of one or more organic solvents, to form a chemical complex; (6) adding the second set of one or more mineral acids to the chemical complex to quench the ongoing reaction to yield Z-9-hexadecenoic acid; (7) reacting the Z-9-hexadecenoic acid with one or more reducing agents in the presence of third set of one or more organic solvents to form a residue; and (8) adding the first set of one or more mineral acids to the residue to quench ongoing reaction to yield Z-9-hexadecenol.

In another embodiment of the present invention, the process for preparation of Z-9-hexadecenol further comprises purification of the Z-9-hexadecenoic acid. The steps included: reacting toluene and zinc chloride with the Z-9-hexadecenoic acid for a duration of 6 hours at a temperature of 65 to 70 °C; filtering outcome of the previous step at a lower temperature of 25 to 30 °C; and removing solvent under vacuum below 50 °C to produce Z-9-hexadecenoic acid.

In further embodiment of the purification of the Z-9-hexadecenoic acid, a second round of purification of Z-9-hexadecenoic acid is included having following steps: adding methanol and sodium methoxide to the Z-9-hexadecenoic acid at a cooled temperature of 10 to 15 °C to obtain a precipitate; performing distillation of the precipitate to remove excess methanol at a temperature of 25 to 30 °C; acidifying the precipitate; and extracting the Z-9-hexadecenoic acid with one or more organic solvents.

BRIEF DESCRIPTION OF THE ACCOMPANYING DRAWING

The other objects, features and advantages will occur to those skilled in the art from the following description of the preferred embodiment and the accompanying drawing in which:

Figure 1 is a flow diagram illustrating steps of the process for preparation of Z-9-hexadecenol, according to one embodiment.

Although specific features of the present invention are shown in some drawings and not in others, this is done for convenience only as each feature may be combined with any or all of the other features in accordance with the present invention.

DETAILED DISCUSSION OF THE INVENTION

Unless otherwise defined herein, scientific and technical terms used in connection with the present disclosure shall have the meanings that are commonly understood by those of ordinary skill in the art. Further, unless otherwise required by context, singular terms shall include the plural and plural terms shall include the singular. Generally, nomenclatures used in connection with techniques of chemistry described herein are those well-known and commonly used in the art. In case of conflict, the present specification, including definitions, will control. The materials, methods, and examples are illustrative only and not intended to be limiting.

It must be noted that, as used in the specification and the appended claims, the singular forms “a,” “an” and “the” include plural referents unless the context clearly dictates otherwise.

The term “comprising” as used herein is synonymous with “including” or “containing,” and is inclusive or open-ended and does not exclude additional, unrecited members, elements or process steps.

The present invention discloses a process for preparing Z-9-hexadecenol.
In one of the embodiments of the present invention, the process broadly includes following steps:
a) preparation of 9-oxononanoic acid: from sodium periodate oxidation of aleuritic acid;
b) preparation of phosphonium salt: reacting primary alkyl halide of heptane with triphenylphosphine in presence of first set of organic solvent(s);
c) Wittig reaction: mixing the phosphonium salt with 9-oxononanoic acid in the presence of base(s) and a second set of organic solvent(s), to form Z-9-hexadecenoic acid; and
d) reduction of Z-9-hexadecenoic acid: with suitable reducing agent(s) and a third set of organic solvent(s) to form the desired Z-9-hexadecenol.
Structure of Z-9-hexadecenol:

The flow diagram given in Figure1 provides the detailed steps of the present process (100), according to one embodiment of the present invention.

A. Preparation of 9-oxononanoic acid

The first stage of the process is preparation of the 9-oxononanoic acid. The stage includes three steps.

Hydroxides of sodium or potassium are reacted with aleuritic acid to form respectively, sodium aleuritate and potassium aleuritate at step 102. Alternatively, carbonates of sodium or potassium are reacted with aleuritic acid to form respectively, sodium aleuritate and potassium aleuritate. The reaction was carried out for a duration of 1 hour at temperature ranging from 10 to 15 °C. Either of the sodium aleuritate and potassium aleuritate so produced at this step could be used in step 104.

The sodium aleuritate or potassium aleuritate was oxidised with sodium periodate at step 104. As aforementioned, either of the sodium aleuritate and potassium aleuritate give the similar output. The process of oxidization is carried out at temperature of 15 °C.

The oxidized sodium aleuritate or potassium aleuritate is hydrolysed with first set of mineral acid(s) to form 9-oxononanoic acid at step 106. The first set of mineral acid(s) used herein are selected from a group consisting of dilute HCl and dilute H2SO4.

In an alternative embodiment, the step of preparation of the 9-oxononanoic acid is skipped and the 9-oxononanoic acid is taken directly for the next stage.

B. Preparation of phosphonium salt

Second stage of the process is preparation of phosphonium salt. During the stage, primary alkyl halide is allowed to react with triphenylphosphine in presence of first set of organic solvent(s) at step 108.
The reaction works well if the alkyl halide is primary group, however it is usually poor with secondary alkyl halide. Tertiary alkyl halide cannot form the phosphonium salt. Presently preferred source of alkyl halide is a primary alkyl halide, where the halide component of the primary alkyl halide can either be chloride or bromide or iodide.

In a preferred embodiment, primary halides of heptane are reacted with triphenylphosphine in presence of the first set of organic solvent(s) to form phosphonium salt. The reaction is carried out at temperature maintained between 50 to 120 °C and for a duration ranging between 12 to 24 hours. However, the preferred range of temperature is between 82 to 86 °C, while preferred range of duration is between 16 to 20 hours.

The first set of organic solvent(s) are selected from a group consisting of toluene, benzene, tetrahydrofuran (THF), dimethylformamide (DMF), acetonitrile and dimethyl sulfoxide (DMSO). However, the toluene and acetonitrile are preferably used in this process.

Once the desired phosphonium salt is formed the next set of reactions are performed.

C. Wittig Reaction

The phosphonium salt is reacted with the 9-oxononanoic acid to form a chemical complex at step 110. The reaction is carried out in the presence of base(s) and a second set of organic solvent(s). The temperature being maintained during the reaction ranges between -30 to 0 °C and for a duration of 2 to 4 hours. The preferred temperature range is between -10 to 0 °C, while the preferred duration ranges between 2 to 3 hours.

The base(s), used during reaction of the phosphonium salt with the 9-oxononanoic acid, are selected from a group consisting of sodium hydride, sodium methoxide, sodium ethoxide, triethylamine, n-butyllithium and sodium amide. However, more preferably n-butyllithium or sodium hydride is used.

The second set of organic solvent(s) are selected from a group consisting of DMSO, THF and diethyl ether. The preferred organic solvents are DMSO and THF.

Second set of mineral acid(s) is/are added to the chemical complex, formed at step 110, to quench the ongoing reaction to yield Z-9-hexadecenoic acid at step 112. The second set of mineral acid(s) are selected from a group consisting of dilute HCl, dilute H2SO4 and ammonium chloride solution. The acid wash which effects a phase separation and causes decomposition of the complex and subsequent yield of the Z-9-hexadecenoic acid.

D. Preparation of Z-9-hexadecenol
Final stage of the process is preparation of the Z-9-hexadecenol using the Z-9-hexadecenoic acid.

The Z-9-hexadecenoic acid is reacted with reducing agent(s) in the presence of third set of organic solvent(s) to form a residue at step 114. The reducing agent(s) are selected from a group consisting of lithium aluminium hydride (LAH), borane dimethylsulfide (BMS), mixture of sodium borohydride and boron trifluoride diethyl etherate. More preferably LAH and BMS are used. Further, the third set of organic solvents are selected from a group consisting of THF and diethyl ether.

The specifics of the temperature and duration provided for the step 114 is as following: the temperature being maintained between 0 to 10 °C, preferably between 5 to 10 °C, and reaction was carried out for a duration of 3 to 10 hours, preferably 5 to 8 hours.

The first set of mineral acid(s) is/are added to the residue to quench ongoing reaction to yield the desired Z-9-hexadecenol at step 116. The acid wash which effects a phase separation of organic solvent containing Z-9-hexadecenol.

Reaction schemes
(RS 1)

(RS 2)

In an another embodiment, the steps of preparation of the 9-oxononanoic acid are skipped (steps 102-106). Readymade 9-oxononanoic acid being reacted with the phosphonium salt at step 110.
(RS 3)

In yet another embodiment, the 9-oxononanoic acid is prepared following the steps 102 to 106, while the step of 108 is skipped and the phosphonium salt is not prepared and a readymade phosphonium salt is used at the step 110.
(RS 4)

In yet another embodiment, the steps of 102, 104, 106, 108 are skipped. The readymade 9-oxononanoic acid and phosphonium salt are used at the step 110.

In a further embodiment of the present invention, a purification protocol for the purification of the Z-9-hexadecenoic acid is added. The following steps for purification are included:

(a) reacting toluene and zinc chloride with Z-9-hexadecenoic acid for a duration of 6 hours at a temperature of 65 to 70 °C;
(b) filtering outcome of the previous step at a lower temperature of 25 to 30 °C; and
(c) removing solvent under vacuum below 50 °C to produce Z-9-hexadecenoic acid.

In another embodiment of the purification protocol, the purification process is further augmented with second round of purification of Z-9-hexadecenoic acid. The steps of the second round of purification include:

(a) adding methanol and sodium methoxide to the Z-9-hexadecenoic acid at a cooled temperature of 10 to 15 °C to obtain a precipitate;
(b) performing distillation of the precipitate to remove excess methanol at a temperature of 25 to 30 °C;
(c) acidifying the precipitate; and
(d) extracting the Z-9-hexadecenoic acid with one or more organic solvents.

EXAMPLES

The present invention is explained further in the following specific examples which are only by way of illustration and are not to be construed as limiting the scope of the invention.

Example- I: Preparation of 9-Oxononanoic acid

A five litre multineck flask equipped with a reflux condenser, mechanical stirrer, thermometer and addition funnel were used. 26.2g of sodium hydroxide in 1600ml of water was added to the flask followed by addition of 200g of aleuritic acid and the suspension stirred for 1 hour at 10 to 15 °C. To the resulting suspension of sodium aleuritate was added 160.2g of sodium periodate in 1600ml of water over 1hour, without allowing the temperature to raise above 15 °C. 500ml of dichloromethane (DCM) was then added and the mixture stirred for a further 2 hours at 15 °C. A further 600ml of DCM and 200ml of saturated aqueous sodium bicarbonate were added and the mixture vigorously stirred for half an hour. The precipitated sodium iodate was removed by filtration and the DCM layer was separated. The aqueous phase was further washed with 500ml of DCM and separated. The aqueous phase was acidified with 200ml of dilute HCl to adjust pH 2 to 3 and extracted with 2X1000ml of ethyl acetate. Combined ethyl acetate layer was washed with 500ml of saturated sodium chloride solution and dried over anhydrous sodium sulphate. Removal of the ethyl acetate in vacuum below 40 °C to obtain 110.5g of 9-oxononanoic acid.

Example- II: Synthesis of heptyltriphenylphosphonium bromide

A three litre multineck flask equipped with a reflux condenser, mechanical stirrer, thermometer and addition funnel were used. 300g of 1-bromoheptane, 541.5g of triphenylphosphine and 900ml of acetonitrile was added to the flask and reaction mixture refluxed for 20 hours at 82 to 86 °C. Reaction was monitored by thin layer chromatography (TLC), once completion of the reaction the excess solvent was removed by rotary vacuum under reduced pressure. Slowly, 1500ml of hexane was added to the mass, cooled to 25 to 30 °C and stirred for 3 hours. Solidified mass was filtered and washed with 150ml of fresh hexane. Separated the wet solid, slurried with1000ml of hexane and stirred for 1 hour. Filtered and washed the solid with 150ml of hexane and dried under vacuum at 40 to 45 °C to obtain 701.5g of wittig salt.

Example- III: Preparation of Z-9-hexadecenoic acid

A three litre multineck flask equipped with a condenser, addition funnel, thermometer, nitrogen inlet and calcium chloride drying tube were used. 59.4g of 60% sodium hydride was added through solid funnel followed by addition of 260ml of DMSO. The reaction mixture was heated for 1 hour at 55 to 60 °C and cooled to room temperature and 1430ml of THF was added. The reaction mixture was cooled below 10 °C and 300.4g of heptyltriphenylphosphonium bromide was added portion wise without raising temperature more than 15 °C. The reaction mass was stirred for 1 hour at same temperature. 110.0g of 9-oxononanoic acid diluted with 220ml of THF was added drop wise and the temperature was maintained at -5 to 0 °C during the addition. The reaction mixture was allowed to room temperature and stirred for 3 hours. The reaction was monitored by Gas chromatography (GC). The reaction mass was cooled below 15 °C, dilute with 330ml of water and acidified with 220ml of dilute HCl to reach pH 2 to 3. Stirred the reaction mass for further 15minutes and separated the THF layer. Re-extracted the aqueous layer with 660ml of ethyl acetate. Combined organic layer was washed with 440ml saturated sodium chloride solution and dried over anhydrous sodium sulphate. Removal of the organic layer in vacuum below 40 °C obtain crude Z-9-hexadecenoic acid. To this added, 1100ml of hexane, 211.2g of zinc chloride and heated to 60 to 65 °C for 6 hours. Cooled the reaction mass to 25 to 30 °C and filtered insoluble on high flow bed. Concentrated the organic layer under vacuum below 40 °C followed by high vacuum distillation to obtain 75.5g of Z-9-hexadecenoic acid.

To this, 375ml of methanol was added and cooled to 10 to 15 °C. Further to this, 111.6g of 25% sodium methoxide was added and stirred for 1 hour at 10 to 15 °C. Distilled the excess methanol under vacuum, cooled to 25 to 30 °C. Next to this, added 375ml of hexane and stirred for 1 hour. Precipitate formed was filtered, washed with fresh hexane and dried under vacuum. Added 150ml of dilute HCl to reach pH 1 to 2 and extracted with 2X300ml of ethyl acetate. The combined organic layer was washed with 300ml of water and with 300ml of saturated sodium chloride solution. Further, the organic layer is dried over anhydrous sodium sulphate and solvent was removed under vacuum below 40 °C to obtain 61.2g of Z-9-hexadecenoic acid.

Example- IV: Preparation of Z-9-hexadecenol

A one litre multineck flask equipped with a condenser, addition funnel, thermometer, nitrogen inlet and calcium chloride drying tube were used. 60g of Z-9-hexadecenoic acid and 480ml of THF was added to the flask. Reaction mixture was cooled to 10 to 15 °C and 11.06g of LAH was added portion wise without allowing the temperature to raise above 15 °C. The reaction mixture was allowed to room temperature and stirred for 8 hours and reaction monitored by GC. The reaction mass cooled 10 to 15 °C, quenched with 140ml of water, acidified with 140ml of dilute HCl to reach pH 1 to 3. Separated the THF layer and re-extracted the aqueous layer with 300ml of ethyl acetate. Combined organic layer was washed with 200ml of 5% sodium bicarbonate solution followed by 200 ml of saturated sodium chloride solution and dried over anhydrous sodium sulphate. Concentrated the organic layer in vacuum below 40 °C, followed by high vacuum distillation to obtain 45.2g of Z-9-hexadecenol.

,CLAIMS:WE CLAIM:
1. A process for preparation of Z-9-hexadecenol, comprising steps of:

reacting one of hydroxides of sodium and carbonates of sodium and one of hydroxides of potassium and carbonates of potassium, with aleuritic acid to form respectively, sodium aleuritate and potassium aleuritate, where the reaction is allowed to occur for a duration of 1 hour at temperature ranging from 10 to 15 °C;

oxidizing the one of sodium aleuritate and potassium aleuritate with sodium periodate, wherein the oxidization is performed at temperature of 15 °C;

hydrolyzing the oxidized one of sodium aleuritate and potassium aleuritate with first set of one or more mineral acids to form 9-oxononanoic acid,

wherein the first set of one or more mineral acids are selected from a group consisting of dilute HCl and dilute H2SO4;

reacting primary halides of heptane with triphenylphosphine in presence of first set of one or more organic solvents to form phosphonium salt,

wherein the first set of one or more organic solvents are selected from a group consisting of toluene, benzene, tetrahydrofuran (THF), dimethylformamide (DMF), acetonitrile and dimethyl sulfoxide (DMSO),

wherein the reaction is carried out at temperature maintained between 50 to 120 °C, more preferably between 82 to 86 °C, for a duration ranging between 12 to 24 hours, more preferably between 16 to 20 hours;

reacting the phosphonium salt with the 9-oxononanoic acid, in the presence of one or more bases and a second set of one or more organic solvents, to form a chemical complex;

adding second set of one or more mineral acids to the chemical complex to quench the ongoing reaction to yield Z-9-hexadecenoic acid from the chemical complex;

reacting the Z-9-hexadecenoic acid with one or more reducing agents in the presence of third set of one or more organic solvents to form a residue; and

adding the first set of one or more mineral acids to the residue to quench ongoing reaction to yield Z-9-hexadecenol.

2. The process as claimed in claim 1, wherein the one or more bases, used during reaction of the phosphonium salt with the 9-oxononanoic acid, are selected from a group consisting of sodium hydride, sodium methoxide, sodium ethoxide, triethylamine, n-butyllithium and sodium amide.

3. The process as claimed in claim 1, wherein the second set of one or more organic solvents are selected from a group consisting of DMSO, THF and diethyl ether,

4. The process as claimed in claim 1, wherein the reaction of the phosphonium salt with the 9-oxononanoic acid is carried out at a temperature ranging between -30 to 0 °C, preferably between -10 to 0 °C, for a duration of 2 to 4 hours, preferably 2 to 3 hours.

5. The process as claimed in claim 1, wherein the second set of one or more mineral acids are selected from a group consisting of dilute HCl, dilute H2SO4 and ammonium chloride solution.

6. The process as claimed in claim 1, wherein the one or more reducing agents are selected from a group consisting of lithium aluminium hydride (LAH), borane dimethylsulfide (BMS), mixture of sodium borohydride and boron trifluoride diethyl etherate.

7. The process as claimed in claim 1, wherein the third set of organic solvents are selected from a group consisting of THF and diethyl ether.

8. The process as claimed in claim 1, wherein reacting the Z-9-hexadecenoic acid with one or more reducing agents in presence of the third set of one or more organic solvents is carried out a temperature ranging between 0 to 10 °C, preferably between 5 to 10 °C, and for a duration of 3 to 10 hours, preferably 5 to 8 hours.

9. The process as claimed in claim 1, further comprises purification of the Z-9-hexadecenoic acid yielded:
reacting toluene and zinc chloride with the Z-9-hexadecenoic acid yielded from the chemical complex for a duration of 6 hours at a temperature of 65 to 70 °C;
filtering outcome of the previous step at a lower temperature of 25 to 30 °C; and
removing solvent under vacuum below 50 °C to produce Z-9-hexadecenoic acid.

10. The process as claimed in claim 9, further comprises second round of purification of Z-9-hexadecenoic acid:
adding methanol and sodium methoxide to the Z-9-hexadecenoic acid at a cooled temperature of 10 to 15 °C to obtain a precipitate;
performing distillation of the precipitate to remove excess methanol at a temperature of 25 to 30 °C;
acidifying the precipitate; and
extracting the Z-9-hexadecenoic acid with one or more organic solvents.

Dated this the 6th day of July 2016

Signature

KEERTHI JS
Patent Agent (IN/PA 1729)
Agent for the Applicant