An Expedient Synthesis of Pyrrole Derivatives by Reaction of Lithiated Methoxyallenes with Imines

Abstract

Addition of lithiated methoxyallene 2 to imines provided the expected allenyl amines in good yield. These could be cyclized with base or with silver nitrate to a variety of 2,5-dihydropyrrole derivatives. Selected examples describe their conversion to pyrrolidin-3-ones or 3-methoxypyrroles. Most importantly, this [3 + 2]cyclization method could also be applied to the synthesis of 2,5-disubstituted derivatives such as 26-28 and also to the preparation of the enantiopure compound 23.