2′-Substituted 1′-(2-dimethylcarbamoylethyl)-3′-spirocycloalkanoindolines: synthesis and conformational analysis of the propanamide fragment

Abstract

2′-Substitued 1′-(2-dimethylcarbamoylethyl)-3′-spirocycloalkanoindolines (2a–f) have been obtained by a phase-transfer attack of 3-chloro-NN-dimethylpropanamide on the indolines (1a–f). ¹H N.m.r. spectra of the nitrogen side chain in compounds (2a–f) show an ABCD proton system for the CH₂–CH₂–CON fragment. Conformational analyses of this fragment for (2a–f) are given and the conformer populations discussed in terms of the bulky ring and the 2′-substituent. Conformational analysis of the CH–CH₂–Ph fragment in the indoline (1h) is also given.