A novel synthesis of unsaturated spiro compounds based on reactions of bifunctional organometallic reagents.

Abstract

Z-allylic dibromides regio- and stereoselectively prepared were reacted with the sodium enolate of ethyl acetoacetate or di(α-ethoxyvinyl)cuprate to yield, after hydrolysis, and decarboxylation in the case where the enolate of ethylacetoacetate was the nucleophile, the corresponding ketones. After reduction and bromination, the products were converted into the appropriate organometallic compounds and reacted with selected cyclic anhydrides and β-halo-α,β-unsaturated cyclic ketones. The spiro compounds so obtained are key intermediates for the synthesis of naturally occurring spiro sesquiterpenes.