Reaction of cyclohexanones imines with substituted nitroolefins. New synthesis of tetrahydroindole derivatives

Abstract

The Michael-type addition of cyclohexanones imines, reacting as their secondary enamine tautomers, to β-substituted nitroolefins is followed by a cyclization reaction with elimination of the nitro group to afford substituted tetrahydroindoles. When a 2-methylcyclohexanone imine is reacted, an unexpected inversion of the regioselectivity is observed when compared with β-substituted ethylenic esters. thus allowing to obtain also substituted tetrahydroindoles.