Suppression of the Wolff Rearrangement of an Unstrained α-Carbonyl Carbene by CO and O₂ in Low-Temperature Matrices

Abstract

Photolysis of matrix-isolated dimethyl diazomalonate (1) in low-temperature argon matrices resulted in a rapid photoinduced Wolff rearrangement to methoxy(methoxycarbonyl)ketene (3). When the photolysis was carried out in pure CO matrices or argon matrices containing carbon monoxide or dioxygen, the reaction pathway was diverted by trapping of the intermediate carbene (2). With dioxygen, a carbonyl oxide intermediate was detected by u.v.-visible spectroscopy. The relative reactivity of carbene (2) with CO and O₂ suggests that it was generated and trapped in a singlet state.