Synthesis of quinolizidines and indolizidines via an intramolecular Mannich reaction

Abstract

Acid treatment of the addition products (13) of an aminopentanal or aminobutanal diethyl acetal and an α,β-unsaturated ketone gave the quinolizidin-2-ones (11), (12), (20), (36), and (37) and the indolizidin-7-ones (9), (10), (16)–(19), (34), and (35) respectively. The ratios of stereoisomers obtained were rationalised by a consideration of the relative stabilities of the transition states and the effect of steric hindrance in the Mannich cyclisation.