Synthesis of triconjugated dienones and novel intermediates used in said process

摘要

Described is a process for preparing triconjugated dienones defined according to the structure: <IMAGE> wherein R1 represents C1-C8 alkyl, phenyl or phenyl methyl and wherein R2 represents hydrogen or C1-C5 lower alkyl; and wherein the wavy lines are indicative of a "cis" or a "trans" juxtaposition of the R2, 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: <IMAGE> (wherein X represents chloro) with a substituted or unsubstituted prenyl ester having the structure: <IMAGE> wherein R3 represents C1-C5 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: <IMAGE> then dehydrohalogenating the compound defined according to the structure: <IMAGE> using an alkali metal carbonate and a dimethylformamide solvent in order to form the novel compound genus having the structure: <IMAGE> 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 compound having the structure: <IMAGE> in order to form the compound having the structure: <IMAGE> the dehydroacyloxylation step taking place in the presence of an alkali metal carbonate and dimethylformamide solvent.