Direct Observation of Carbamoylnitrenes

As the prototype Curtius rearrangement reaction, carbamoyl azide decomposes into aminoisocyanate and molecular nitrogen. However, the key intermediate carbamoylnitrene was previously undetected, even though the decomposition of carbamoyl azides has been studied frequently since its discovery in the 1890s. Upon ArF laser (λ=193 nm) photolysis, the stepwise decomposition of the two simplest carbamoyl azides H2NC(O)N3and Me2NC(O)N3,isolated in solid noble gas matrices, occurs with the formation of the corresponding carbamoylnitrenes H2NC(O)N and Me2NC(O)N. Both triplet species are characterized for the first time by combining matrix-isolation IR spectroscopy and quantum-chemical calculations. Subsequent visible-light irradiations cause efficient rearrangement of these nitrenes into the respective aminoisocyanates. © 2016 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim.