Synthesis of triconjugated dienones and novel intermediates used in said

Abstract

Described is a process for preparing triconjugated dienones defined according to the structure: ##STR1## wherein R.sub.1 represents C.sub.1 -C.sub.8 alkyl, phenyl or phenyl methyl and wherein R.sub.2 represents hydrogen or C.sub.1 -C.sub.5 lower alkyl; and wherein the wavy lines are indicative of a 'cis' or a 'trans' juxtaposition of the R.sub.2, methyl, acyl or vinyl moieties about one or both of the carbon-carbon double bonds which process involves the reaction of an acyl halide with a substituted or unsubstituted prenyl ester having the structure: ##STR2## wherein R.sub.3 represents C.sub.1 -C.sub.5 alkyl in the presence of an aluminum chloride catalyst and a methylene dichloride solvent in order to form a halogen-ester intermediate defined according to the structure: ##STR3## then dehydrohalogenating said halogen-ester intermediate using an alkali metal carbonate and a dimethylformamide solvent in order to form a ketoester having the structure: ##STR4## wherein one of the dashed lines represents a carbon-carbon double bond and the other of the dashed lines represents a carbon-carbon single bond; and then dehydroacyloxylating the ketoester in the presence of an alkali metal carbonate and dimethylformamide solvent in order to form the triconjugated dienone.