Palladium-catalyzed [3 + 3] annulations of 1-alkyl-indolin-2-imines and dialkyl (2-methylenepropane-1,3-diyl) dicarbonates

Abstract

Palladium-catalyzed [3 + 3] annulations of 1-alkyl-indolin-2-imines and dialkyl (2-methylenepropane-1,3-diyl) dicarbonates leading to pyrido[2,3-b]indole derivatives have been developed for the first time, in which the reaction of 1-alkyl-3-alkylindolin-2-imine hydrochlorides with dimethyl (2-methylenepropane-1,3-diyl) dicarbonate provided tetrahydro-2H-pyrido[2,3-b]indoles, and the treatment of N-(1-methylindolin-2-ylidene)benzenesulfonamides with di-tert-butyl (2-methylenepropane-1,3-diyl) dicarbonate gave tetrahydro-1H-pyrido[2,3-b]indoles. The convenient and practical methods afford diverse pyrido[2,3-b]indole derivatives for screening of biological and pharmacological molecules.