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 CO 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.