Photosensitized Oxidation of Alkyl Phenyl Sulfoxides. C−S Bond Cleavage in Alkyl Phenyl Sulfoxide Radical Cations

The 3-cyano-N-methylquinolinium perchlorate (3-CN-NMQ+ ClO4−)-photosensitized oxidation of phenyl alkyl sulfoxides (PhSOCR1R2R3, 1, R1 = R2 = H, R3 = Ph; 2, R1 = H, R2 = Me, R3 = Ph; 3, R1 = R2 = Ph, R3 = H; 4, R1 = R2 = Me, R3 = Ph; 5, R1 = R2 = R3 = Me) has been investigated by steady-state irradiation and nanosecond laser flash photolysis (LFP) under nitrogen in MeCN. Steady-state photolysis showed the formation of products deriving from the heterolytic C−S bond cleavage in the sulfoxide radical cations (alcohols, R1R2R3COH, and acetamides, R1R2R3CNHCOCH3) accompanied by sulfur-containing products (phenyl benzenethiosulfinate, diphenyl disulfide, and phenyl benzenethiosulfonate). By laser irradiation, the formation of 3-CN-NMQ• (λmax = 390 nm) and sulfoxide radical cations 1•+, 2•+, and 5•+ (λmax = 550 nm) was observed within the laser pulse. The radical cations decayed by first-order kinetics with a process attributable to the heterolytic C−S bond cleavage leading to the sulfinyl radical and an alkyl ...