Heterodiene synthesis. Part XVII. Reactions of 2-oxoindolin-3-ylidene derivatives with enamines: a Michael pathway as an alternative to 1,2- and 1,4-cycloadditions

Abstract

The reactions of enamines with 2-oxoindolin-3-ylidene-acetates and -acetophenones have been studied. With enamines derived from aldehydes the former gave either 1,2- or 1,4-cycloaddition products, as previously described for the latter. However, both substrates gave only Michael-type adducts with enamines derived from cyclopentanone. The mechanism is discussed in terms of both frontier orbital interaction and stabilized dipolar intermediates.