Facile Synthesis of Polysubstituted Indolizines via One‐Pot Reaction of 1‐Acetylaryl 2‐Formylpyrroles and Enals

Abstract

An efficient method for the synthesis of polysubstitutedi ndolizinesh as been developed based on formal [4+ +2] annulation of 1-acetylaryl2 -formylpyrroles with enals, followed by oxidative aromatization. Pyridinetype six-membered rings were constructed in this transformation. This transition metal-free reactionf eatures mild reaction conditions, ab road substrate scope, and excellent functional group tolerance. Notably,t he formyl group is welltoleratedu nder reaction conditions. Scheme1.Representative examples and synthetic methodsfor indolizines.[a] M. Gong, J.Supporting information and the ORCID identification number(s) for the author(s) of this article can be found under: https://doi.

Michael-Aldol Double Elimination Cascade to Make Pyridines: Use of Chromone for the Synthesis of Indolizines

“…Encouraged by our successful [4+2] annulation approach to quinone-indolizine hybrid structures via formation of a pyridine ring, we wondered if adoption of the similar [4+2] cyclization protocol would afford novel indolizines ( 12 ) from chromone ( 1 ) and pyrrole derivatives ( 11 ) through the intermediate A (Scheme b). Notably, it would allow installation of two different acyl groups at the C5 and C7 sites, whereas Huang’s method produced the indolizines having two acyl motifs at the C1 and C3 positions. Here, we wish to describe our results on the synthesis of new indolizines and further functionalization.…”

Base-promoted [4 + 2] annulation of pyrrole-2-carbaldehyde derivatives with β,γ-unsaturated α-ketoesters: syntheses of 5,6-dihydroindolizines

“…In the past two decades, chemists have reported the synthesis of multisubstituted indolizine compounds using coupling strategies for pyrrole derivatives with different alkenes and ketones (Scheme 1a). 7 For example, Kim's group 8 and Zou's group 9 constructed indolizine compounds using N-substituted pyrrole-2-carboxaldehyde derivatives and acetophenone derivatives through [5 + 1] or [4 + 2] cyclization. Recently, Kim and co-worker 10 used quinones and chromones with N-substituted pyrrole-2-carboxaldehyde to construct differently substituted indolizine compounds through [4 + 2] cyclization, respectively.…”