ELECTROCHEMICALLY INDUCED HETERO-[4-CYCLOADDITION REACTIONS BETWEEN 2-VINYLPYRROLES AND BETA-ACCEPTOR-SUBSTITUTED ENAMINES(2])

Recently, we reported on radical cation cycloaddition reactions betwee n 2-vinylindoles and beta-acceptor-substituted enamines, which provide a new pathway to pyrido[1,2-a] indoles.([1]) In order to broaden the synthetic scope of this reaction, we have developed hetero-[4+2]-cyclo addition reactions between a number of readily accessible 2-vinylpyrro les, acting as heterodienes, and beta-acceptor-substituted enamines. T his reaction is induced by electrochemically generated radical cations of either the 2-vinylpyrrole diene or the enamine dienophile. These e lectron-transfer-induced reactions open up a novel route to highly sub stituted indolizines in moderate yields. We propose a mechanism that e xplains both the complete regio-control of this cycloaddition as well as the product formation, irrespective of the inducing radical cation species.