Stereoselective Synthesis of 3‑Carboxy-4,5-dihydropyrroles via an Intramolecular Iminium Ion Cyclization Reaction

An efficient and practical method has been developed for the synthesis of trans-4,5-disubstituted 3-carboxy-4,5-dihydropyrroles via an intramolecular iminium ion cyclization reaction of readily accessible Baylis–Hillman derivatives and aldehydes in moderate to high yield. These new dihydropyrroles could be easily converted to pyrroles or pyrrolidines.