process for the production of ªÿ, ªÿ - ungesaettigten saeuren of vitamin a - series

摘要

An improvement in the process of the parent Specification comprises dehydrating the a -hydroxycarboxylic acid ester using a compound of formula FORM:0916084/IV (b)/1 wherein R is an alkyl, cycloalkyl or aryl radical, R1 is an alkyl or cycloalkyl, X is a phosphorus atom and Y a chlorine atom, the reaction being carried out at an elevated temperature in the presence of an inert organic solvent and quinoline or N,N-dimethylaniline. In examples 5-(21,61,61-trimethyl-cyclohexene-(21) -ylidene) - 3 - methyl-2-hydroxy-pentene-(3)-oic acid methyl ester is dehydrated to 5-(21,61,61-trimethyl - cyclohexadiene - (11,31)-yl)-3-methylpentadiene-(2,4)-oic acid methyl ester using diethyl or di-n-propyl or di-n-butyl or dicyclohexyl monochlorophosphite.