Blue, but Not a Mirage: Stable Aminoketenes by Carbene Carbonylation

摘要

Soon after the preparation and isolation of the first ketene in 1905[1a] efforts were made to prepare ketenes with highly electronegative heteroatom substituents, including examples with oxygen and halogen atoms bonded to the ketene.[1b]-[d], [2], [3] However, these efforts did not yield isolable ketenes, and it was apparent that these species were very reactive. Oxygen-substituted ketenes[2a],[b] were however successfully generated and captured in situ with imines in [2+2] cycloaddition reactions.[2a] These compounds were much later directly observed by IR or UV spectroscopy in frozen matrices[2c] or as transient intermediates in solution,[2d] and were generated in the gas phase.