A new reaction of aminocarbene complexes of chromium upon alkyne insertions: deoxygenation rearrangement of ketene intermediates. Formation and X-ray structure of a tetrahydroindolizine complex

Abstract

Aminocarbene complexes (1) of chromium bearing suitable substituents on nitrogen react with alkynes to give, besides the expected heterocyclic compounds (5) and (6) originating from cascade alkyne–CO insertion–rearrangement reactions, deoxygenation–rearrangement products (8) of ketene intermediates, whereas when nitrogen bears substituents of low migratory aptitude, ketene complexes (4) and their derivatives (7) could be isolated and fully characterized either by spectroscopy or by X-ray Crystallography.