Oxazete intermediate

In the study of the potential energy surface [B3LYP/6-311G+-h(d,p)] for the reaction of the ethynyl radical HC2 with nitric oxides NO and N02, Peeters and co-workers reported that a cyclic 1,2-oxazete intermediate such as 17 may be involved. In the reaction of HC2 and NO, the four-membered cyclic structure 17, precursor of HCN and CO, could reasonably be formed from 16 by means of a ring-closing reaction having an activation barrier of 18 kcal mol-1 (Scheme 2) <1998CPL91>. 

Oxazete-fV-oxide 15 has been postulated as the main intermediate in the mechanism of the unimolecular degradation of nitroethylene 14. The calculated barrier of 205.6 kj mol-1, for the reaction shown in Equation (1), at the B3LYP/6-311+- -G(df,p) level, is close to the experimental energy found in the gas-phase nitroethylene degradation (192.05 kj mol-1) <2001MC163>. 

Durchschein, K., Fabian, W.M.F., Macheroux, P., Zangger, K., Trimmel, G., and Faber, K. (2011) Reductive biotransformation of nitroalkenes via nitroso-intermediates to oxazetes catalyzed by xenobiotic reductase A (XenA). 0 g, Biomol. Chem., 9, 3364-3369. 

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