Vinylnitrene Formation from 3,5-Diphenyl-isoxazole and 3-Benzoyl-2-phenylazirine

Photolysis of 1 in argon-saturated acetonitrile yields 2, whereas in oxygen-saturated acetonitrile small amounts of benzoic acid and benzamide are formed in addition to 2. Similarly, photolysis of 2 in argon-saturated acetonitrile results in 1 and a trace amount of 3, whereas in oxygen-saturated acetonitrile the major product is 1 in addition to the formation of small amounts of benzoic acid and benzamide. Laser flash photolysis of 1 results in an absorption due to triplet vinylnitrene 4 (broad absorption with lambda(max) at 360 nm, tau = 1.8 mu s, acetonitrile) that is formed with a rate constant of 1.2 x 10(7) s(-1) and decays with a rate constant of 5.6 X 10(5) s(-1). Laser flash photolysis of 2 in argon-saturated acetonitrile likewise results in the formation of triplet vinylnitrene 4 but also ylide 5 (lambda(max) at 440 nm, tau = 13 mu s). The rate constant for forming 4 in argon-saturated acetonitrile is 1.6 x 10(7) s(-1). In oxygen-saturated acetonitrile, vinylnitrene 4 reacts to form the peroxide radical 6 (lambda(max) 360 nm, similar to 0.7 mu s, acetonitrile) at a rate of 2 x 10(9) M-1 s(-1). Density functional theory calculations were performed to aid in the characterization of vinylnitrene 4 and peroxide 6 and to support the proposed mechanism for the formation of these intermediates.