GB979523A - Improvements in or relating to the production of terpene esters and alcohols - Google Patents

Abstract

Terpene esters are prepared by treating an allylic terpenic halide or dihalide with a carboxylic acid salt in the presence of a nitrogen base catalyst or a salt thereof; the esters obtained may subsequently be hydrolysed to the corresponding terpene alcohols. (As used herein, the expression "allylic terpinic halide" denotes allylic chlorides or bromides derived from terpenes in which the terpene allyl residue consists of 10 carbon atoms, and the expression "nitrogen base" denotes a compound containing nitrogen which can add on HX, where X is chlorine or bromine, and can be regenerated by removal of the HX group). In a modification, an amine or ammonium salt of a carboxylic acid is used both as the carboxylic acid salt reactant and as the nitrogen base salt catalyst. The terpenic halide may be acyclic, or mono- or bicyclic. The carboxylic acid salts may be those of aliphatic, carbocyclic or heterocyclic, and mono- or poly-, carboxylic acids, including hydroxy acids, chloracids and amino acids. The salts may be metal salts, e.g. alkali or alkaline earth metal, or lead, nickel, copper, manganese or aluminium salts. The nitrogen base catalyst may be ammonia or hydroxylamine, or an amine, amidine, amide, oxime, hydrazone, semicarbazide or imine. Esterification may be effected at room temperature and above, and inert solvents may be present. Numerous examples of terpene ester preparations are given, the allylic halide reactants being derived from myrcene, ocimene, limonene, 3-p-menthene, a -pinene and a -terpineol, and the carboxylic acid salt reactants being sodium acetate, chloracetate, butyrate, benzoate, lactate, oxalate and fumarate, the sodium salt of crude tall oil and calcium salt of tall oil fatty acid, ammonium acetate and isovalerate, potassium acetate and hydrogen phthalate, lead acetate, cupric acetate, nickel formate and aluminium acetate; there are used as catalysts a wide variety of amines, hydroxylamine, urea, guanidine, acetamide, brucine, acetamidine, dimethylglyoxime and ammonium chloride. The esters are, in some cases, hydrolysed to liberate the corresponding terpene alcohols or diols. In some cases mixtures of cis and trans isomers of the esters or alcohols are obtained which are resolved by vapour phase chromatography. 2-Chloro-8-acetoxy-2, 6-dimethyl-6-octene (obtained in Example 15) on heating with ammonium acetate is converted into a mixture of geranyl acetate and its isopropenyl end-group isomer. The terpenic allylic halides used as starting material are prepared: (a) by adding hydrogen halide to double-bonds of suitable terpenes in the presence of cuprous chloride or bromide, and (b) by reacting a suitable terpene directly with halogen, generally in the presence of sodium bicarbonate. Specification 979,524 is referred to.