GB678515A - Process for the production of vitamin a ethers and esters - Google Patents

Abstract

A process for the production of vitamin A ethers or esters of the formula <FORM:0678515/IV (b)/1> wherein R is an alkyl or acyl group containing less than 8 carbon atoms comprises heating in an inert atmosphere at a temperature not exceeding the boiling-point of pyridine a compound of the formula A.CH(OH).CH: CH.CMe(OH).CH2.CH2.OR or A.CH(OH).CH : CH.CMe : CH.CH2OR with a salt of a tertiary base, e.g. of pyridine, quinoline or dimethyl-aniline in the presence of pyridine as a solvent. Other suitable bases are a -, b - or g -picolines, other alkyl pyridines, isoquinoline, acridine, or trialkylamines, e.g. trimethyl-, triethyl-, trinaphthyl- and triallylamines, their hydrohalides, acid sulphonates, benzene sulphonates, and trichloracetates being specified. The pyridine solvent may be mixed with allyl formate, acetate or propionate, geranyl acetate, diallyl ether or other allyl ethers, geranyl ethers or benzyl esters or ethers, which prevent decomposition of the products into anhydrovitamin A. In examples: (1) a compound of general formula I, where R represents ethyl, is refluxed with pyridine hydrobromide to yield the ether of formula III, which is purified by partition between 90 per cent methanol and petroleum ether and then by chromatography; (2) the process of (1) is repeated with a mixture of pyridine and diallyl ether as solvent; (3) a carbinol of the formula II where R represents methyl is dehydrated to give vitamin A methyl ether by heating with pyridine, hydrogen bromide, diallyl ether, and, as antioxidant, hydroquinone; (4) and (5) vitamin A acetate is obtained by refluxing a compound of formula II where R represents -CO.CH3 with pyridine hydrochloride and pyridine. The product may be purified by partition between 90 per cent methanol and n-pentane or by chromatography, hydroquinone being added to the reaction mixture in (4); (6) the process of (5) is repeated using pyridine p-toluene sulphonate in place of pyridine hydrochloride. The Specification as open to inspection under Sect. 91 specifies also salts of morpholine. This subject-matter does not appear in the Specification as accepted.