HETEROSUBSTITUTED 4-VINYLIMIDAZOLES - PREPARATION AND DIELS-ALDER REACTIONS

摘要

The Diels-Alder reactions of vinylimidazole derivatives provide an expedient stereocontrolled entry into polysubstituted tetrahydrobenzimidazole derivatives. Prior studies from our group have described methods for postcycloaddition functionalization of these adducts, however, in several cases we have been unable to achieve appropriate elaboration of cycloadducts and have sought alternatives. To circumvent this problem we have investigated pre-cycloaddition functionalization through the preparation of vinyl-substituted derivatives. Initial studies with vinyl halides or silyl enol ethers were compromised either by poor yields or postcycloaddition elimination. However, vinylsilanes and vinylstannanes participate in Diels-Alder reactions with retention of the heterosubstituent and provide a means for further elaboration, for example through Fleming-Tamao oxidation.