Experimental and theoretical investigation of benzyl-e?‘?-pyrrolylketene, one- step procedure for preparing of new e???-lactams by [2+2] cycloaddition reaction

摘要

3-Phenyl-2-(1-e???-pyrrol-1-yl) propanoic acid has been used as a ketene source in synthesizing of monocyclic-2-azetidinones. Hindrance in ketene and imines successfully controlled the diastereoselectivity of the reaction. For example, in some cases only one isomer was achieved. By using Mukaiyama reagent, the leaving group in acid was activated and the by-products were separated by simple aqueous work-up. DFT calculation indicated that the benzyl-e?‘?-pyrrolylketene has nonconjugated structure and the pyrrolyl ring is perpendicular to the ketene plane in both the twisted and planar structures.