Competition Between C_α -S and C_α -C_β Bond Cleavage in β-Hydroxysulfoxides Cation Radicals Generated by Photoinduced Electron Transfer.

ABSTRACT: A kinetic and product study of the 3-cyano-N-methyl-quinolinium photoinduced monoelectronic oxidation of a series of β-hydroxysulfoxides has been carried out to investigate the competition between C_α -S and C_α -C_β bond cleavage within the corresponding cation radicals. Laser flash photolysis experiments unequivocally established the formation of sulfoxide cation radicals showing their absorption band (λ _max ≈ 520 nm) and that of 3-CN-NMQ^• (λ _max ≈ 390 nm). Steady-state photolysis experiments suggest that, in contrast to what previously observed for alkyl phenyl sulfoxide cation radicals that exclusively undergo C_α -S bond cleavage, the presence of a β-hydroxy group makes, in some cases, the C_α -C_β scission competitive. The factors governing this competition seem to depend on the relative stability of the fragments formed from the two bond scissions. Substitution of the β-OH group with -OMe did not dramatically change the reactivity pattern of the cation radicals thus suggesting that the observed favorable effect of the hydroxy group on the C_α -C_β bond cleavage mainly resides on its capability to stabilize the carbocation formed upon this scission.

SUBMITTER: Lapi A 

PROVIDER: S-EPMC9290654 | biostudies-literature | 2021 Nov

REPOSITORIES: biostudies-literature