Direct observation of methoxycarbonylnitrene

The simplest alkoxycarbonylnitrene, CH₃OC(O)N, has been generated through laser (266 and 193 nm) photolysis of CH₃OC(O)N₃ and CH₃OC(O)NCO and subsequently characterized by IR (¹⁵N, D-labelling) and EPR (|D/hc| = 1.66 cm^-1 and |E/hc| = 0.020 cm^-1) spectroscopy in cryogenic matrices. Two conformers of the nitrene, with the CH₃ group being in syn or anti configuration to the C[double bond, length as m-dash]O bond, have been unambiguously identified. Further UV light irradiation (365 nm) of the nitrene results in isomerization to CH₃ONCO, completing the frequently explored mechanism for the Curtius-rearrangement of CH₃OC(O)N₃.