Novel reactions of indolenines

Abstract

3,3-Disubstituted indolenines readily undergo addition by Grignard reagents to afford 2,3,3-trisubstituted indolines; the reaction is stereospecific if one of the 3-substituents is considerably larger than the other. The diastereoisomeric indolines may be obtained by hydrogenation of the appropriate 2,3,3-trisubstituted indolenines. 2,3,3-Trialkylindolenines are alkylated by Grignard reagents at the α-methylene group of the 2-alkyl substituent. Such indolenines easily autoxidise, e.g., 2-ethyl-3,3-dimethylindolenine affords 2-acetyl-3,3-dimethylindolenine. Mass and n.m.r. spectra of most of the indolenines and indolines are recorded.