The reaction of nitroso oxides with olefins: Concerted or nonconcerted addition?

The mechanism of the interaction of nitroso oxides (RNOO) with olefins was studied at MCQDPT2/6-311+G(3df, 2p)//CASSCF(10; 9)/6-311G(d) level of theory. The following reaction channels were considered: (1) (3 + 2)-cycloaddition and nonconcerted biradical addition of nitroso oxide (2) through the terminal oxygen atom and (3) through the nitrogen atom to the C=C multiple bond. It was shown for the cases of (A) cis/trans-HNOO + C2H4, (B) cis/trans-HNOO + C2F4, (C) cis/trans-PhNOO + C2H4, and (D) cis/trans-PhNOO + C2H3CH3 model systems that the typical reaction of nitroso oxides with alkenes was cycloaddition. For olefins with a decreased electron density at the multiple bond, as in system B, a substantial contribution of the one-center mechanism with the formation of biradical intermediates is possible.