Asymmetric Synthesis of Chiral Pyrrolizine‐Based Triheterocycles by Organocatalytic Cascade Aza‐Michael–Aldol Reactions

Abstract

Abstract New, chiral pyrrolizine‐based triheterocycles were obtained by the organocatalytic asymmetric cascade aza‐Michael–aldol reaction of α‐branched α,β‐unsaturated aldehydes with 2‐(trifluoroacetyl)pyrroles. High enantioselectivities (90–95 % ee ) and excellent diastereoselectivities ( dr up to >20:1) were achieved by employing this synthetic strategy. The highly functionalized, trifluoromethyl‐substituted cascade products have three consecutive stereogenic centers that include two chiral quaternary centers. The chemoselective stepwise Suzuki cross‐coupling reaction of the cascade products with two different arylboronic acids provided chiral pyrrolizine‐based triheterocycles that contain two distinct aryl substituents in good yields.