FORM 2
THE PATENT ACT 1970
&
The Patents Rules, 2003
PROVISIONAL / COMPLETE SPECIFICATIO
(See section 10 and rule 13)
1. TITLE OF THE INVENTION:
"An Improved Process for preparing 4-n-hexyl resorcinol and 4-n-hexylresorcinol obtained therefrom."
2. APPLICANT(S)
(a) NAME: SUDARSHAN CHEMICAL INDUSTRIES LTD.
(b) NATIONALITY: Indian Company registered under the provisions
of the Companies Act, 1956
(c) ADDRESS: 162, Wellesley road,
PUNE-411001, Maharashtra State, India
3. PREAMBLE TO THE DESCRIPTION
PROVISIONAL COMPLETE
The following specification describes the The following specification
invention. particularly describes the invention and the
manner in which it is to be performed.
4. DESCRIPTION (Description starts from page 2)
5. CLAIMS: Given on a separate sheet

6. DATE AND SIGNATURE: Given at the end of last page of specification.
7. ABSTRACT OF THE INVENTION: Given on a separate sheet
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Technical Field:
The present invention relates to a preparation of 4-n-hexylresorcinol. More particularly, present invention relates synthesis of 4-n-hexylresorcinol by the reaction of resorcinol with hexanoic acid in the presence of catalyst followed by insitu reduction of intermediate product in presence of Zinc catalyst in aqueous acid solution.
The main object of the present invention is to provide an improved process for the preparation of 4-n-hexylresorcinol.
Another object of the present invention is to make 4-n-hexylresorcinol suitable for commercial production using catalysts that are nonpolluting and easy to handle.
Still further object of the present invention is to make 4-n-hexylresorcinol with high purity and relatively higher yield
Background and Prior Art:
Resorcinols and its derivatives have a wide variety of applications. Alkyl resorcinols and aromatic resorcinols are reported to possess valuable therapeutic and antiseptic properties. In particular, 4-alkyl resorcinol is reported to have skin-beautifying effect with low toxicity and irritation when applied on to human skin. 4-Alkyl resorcinol has also been reported to be used to inhibit browning of foods and beverages. 4-n-hexylresorcinol is an antiseptic and an anthelmintic (Compare US 4093667 and WO2004052827).
In the prior art, 4-n-hexylresorcinol have been prepared by some known methods. One such method is described in US patent no. 1649670, wherein, 4-n-hexylresorcinol is prepared by condensing hexanoic acid with resorcinol and resultant ketone is reduced by using a mercury-zinc amalgam. It is a two-step process, in the first step; resorcinol is being reacted with hexanoic acid in presence of anhydrous Zinc chloride at elevated
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temperatures. The intermediate ketone thus produced is purified by repetitive distillation at around 200°C under 8mm Hg reduced pressure followed by reduction using a zinc-mercury amalgam in dilute Hydrochloric acid to produce the 4-hexyl resorcinol which is then purified by repeated distillation in vacuo at 180-200°C under 8-18 mm pressure and by crystallization in various solvents. The yield of isolated pure product is very low due to formation of side products in both the steps and process seems not to be feasible for commercial production. Moreover, the reduction reaction suffers from the drawback of having to use mercury compounds as catalyst.
U.S. Patent. No. 4093667 has described the preparation of 4-n-hexylresorcinol in two-step process involving, preparing hexyl resorcyl ethers by reacting resorcinol with a hexylating agent such as hexyl halides in the presence of a base, and second, treating the reaction product thus obtained with a catalyst to yield 4-n-hexylresorcinol by a rearrangement process. In the process of step 1 reaction is carried out from about 25 °C to about 175 °C temperature and the reaction temperature of step 2 is from about 150 °C to about 300 °C in presence of acidic catalyst such as alumina, silica alumina, or methanesulfonic acid to obtain the product along with mixture of side products. However, process does not claim isolation of pure product.
Still another approach is disclosed in WO2004052827, wherein, esters of 4-alkyl resorcinol and 4-alkyl resorcinol is prepared by reacting resorcinol with alkyl anhydride at a temperature of 50 to 150 °C in the presence of an acid catalyst such as methane sulfonic acid, sulfuric acid, hydrochloric acid, phosphoric acid, p-toluene sulfonic acid, and acidic ion-exchange resins followed by reducing the products in the presence of a Raney Nickel in an alcoholic medium to obtain mixture of 4-alkyl resorcinol, 4-alkyl resorcinol monoacetate, 4-alkyl resorcinol diacetate. The products were separated on a silica column.
Thus, any method for producing 4-n-hexylresorcinol product with high purity with reasonable good yield which is easier to handle at commercial scale and overcomes the various disadvantages of the prior art procedures, would be very desirable
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Deficiencies of Prior Art:
1. The prior art processes provide low yields due to formation of side reaction products.
2. The process for 4-n-hexylresorcinol either involves rigorous purification steps or non-conventional purification techniques to get pure product which may not have commercial success.
3. Since catalysts used in prior art processes either pyrophoric in nature or element of environmental pollution, its handling, recovery, recycle or disposal involves considerable cautionary measures.
Description of the present invention:
The present invention relates to a process for producing 4-n-hexylresorcinol that comprises preparation by mixing resorcinol with hexanoic acid, and heating the mixture in the presence of catalyst followed by resultant product viz. 4-hexanoyl resorcinol is reduced insitu in presence of a Zinc in dil. Hydrochloric acid medium to provide 4-n-hexylresorcinol.
The 4-n-hexylresorcinol of formula (I) is prepared by reacting resorcinol of formula (II) with hexanoic acid of formula (III) in presence of catalyst at temperature ranging from about 70 °C to 130 °C to give 4-hexanoyl resorcinol of formula (TV). The reaction product of formula (IV) of this reaction is then heated in the presence of a Zinc catalyst in dilute HCl at 70-100°C to give 4-n-hexylresorcinol of formula (I) as shown below.
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According to the present invention, the boron trifluoride etherate is used in part 1 as catalyst wherein, resorcinol is reacted with hexanoic acid. The amount of trifluoride etherate used should be at least of the stoichiometric amount with resorcinol and hexanoic acid to achieve complete conversion into the 4-hexanoylresorcinol in at least 95% of purity by qualitative gas liquid chromatography.
The reduction process of resulting reaction products of part 1 of the present invention is carried out in the presence of activated Zinc powder in dilute HC1.
In the present invention, the reaction mixture obtained after reacting resorcinol and hexanoic acid with boron trifluoride etherate is heated in presence of Zinc/HCl without isolation i.e. 4-hexanoyl resorcinol produced in first part of reaction is not isolated from the reaction mixture and can be carried forward as such for reduction process.
The process typically is carried out over a temperature range of about 70°C -130°C, preferably 90°C - 110°C for part 1 of the process and 70°C -100°C, preferably 80°C -90°C for part 2 of process.
Pressure normally is not an important process condition and the process therefore normally is performed at an ambient pressure.
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Example:
Into a four neck round bottom flask equipped with mechanical stirrer and a condenser were charged Resorcinol (0.9 moles), Hexanoic acid (1.0 to 1.5 moles equivalent) and boron trifluoride etherate (1.0 to 1.5 moles equivalent). The mixture was stirred at room temperature for 15-45 minutes. The mixture was heated slowly to 80 °C -130 °C and maintained at 100-130 °C for period of 10-20 hours. The progress of reaction was monitored by Thin Layer Chromatography (TLC) and Gas liquid Chromatography (GLC). After completion of reaction, the reaction mixture was cooled to 30 °C and 20 wt % hydrochloric acid (6-7 moles equivalent) was added under stirring. Then, into the reaction mass, activated Zinc powder (3-5 moles equivalent) was added and heated to 70-100°C and maintained this temperature for 10-20 hours. The progress of reaction was monitored by Thin Layer Chromatography (TLC) and Gas liquid Chromatography (GLC). After completion of reaction, the reaction mixture was cooled to 30 °C and organic layer was separated out. The crude oily product was washed with water till neutral pH and distilled in vacuum where low boiling fractions are removed and finally 4-n-hexyl resorcinol was distilled out under vacuum (5-9 mm Hg) at 160 to 180 °C. It was further purified by crystallization in n-Hexane to get white to off white crystalline solid (Yield 40-45%) with 98-99% purity by Gas Liquid Chromatography, melts at 65°C -68°C. The product obtained was characterized by elementary analysis, IR and NMR.
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We Claim:
1. An improved process for preparing 4-n-hexylresorcinol of formula (I) is prepared by reacting resorcinol of formula (II) with hexanoic acid of formula (III) in presence of certain catalyst at temperature ranging from about 70 °C to 130 ° C to give 4-hexanoyl resorcinol of formula (IV); the reaction product of formula (IV) of this reaction is then heated in the presence of a Zinc catalyst in dilute HC1 at 70-100°C affords to 4-n-hexylresorcinol of formula (I) as shown below



OH

.OH

2. An improved process for preparing 4-n-hexylresorcinol of formula (I) as claimed in claim 1 wherein, boron trifluoride etherate is used as catalyst in the reaction of resorcinol with hexanoic acid
3. A process as claimed in claim 1 wherein, boron trifluoride etherate is used as catalyst in 1.0-1.5 mole equivalent, preferably 1.2-1.3 mole equivalent
4. A process as claimed in claim 1 wherein, hexanoic acid is used 1.0-1.5 mole equivalent, preferably 1.2-1.3 mole equivalent
5. A process as claimed in claim 1 wherein, reduction is carried out without isolation of 4-hexanoyl resorcinol of formula (IV) from the reaction
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6. A process as claimed in claim 1 wherein, activated Zinc powder used as reduction
catalyst in 3-5 moles equivalent
7. A process as claimed in claim 1 substantially as herein described with reference to
the example and specification

Dated this 22nd day of June, 2007

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Abstract:
The present invention relates to a process for preparing 4-n-hexylresorcinol of formula (I) prepared in the present invention by reacting resorcinol of formula (II) with hexanoic acid of formula (III) in presence of certain catalyst at temperature ranging from about 70 °C to 130 ° C to give 4-hexanoyl resorcinol of formula (IV). The reaction product of formula (IV) of this reaction is then heated in the presence of a Zinc catalyst in dilute HC1 at 70-100°C affords to 4-n-hexylresorcinol of formula (I) as shown below.

The present invention is much safer and useful to make 4-n-hexylresorcinol suitable for commercial production using catalysts that are nonpolluting and easy to handle.