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 having the structure: ##STR2## (wherein X represents chloro) with a substituted or unsubstituted prenyl ester having the structure: ##STR3## 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 the novel intermediate genus defined according to the structure: ##STR4## then dehydrohalogenating the compound defined according to the structure: ##STR5## using an alkali metal carbonate and a dimethylformamide solvent in order to form the novel compound genus having the structure: ##STR6## 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 dehydrocyloxylating the compound having the structure: ##STR7## in order to form the compound having the structure: ##STR8## the dehydroacyloxylation step taking place in the presence of an alkali metal carbonate and dimethylformamide solvent.