Oxidation of #alpha#-sulfonyl selenides: Formation of selenolesters

摘要

Treatment of 7-phenylseleno-7, 12-dihydrobenzo[5, 6][1, 3]thiazepino[3, 2-a]benzimidazole 6, 6-dioxide 7a in CH_2Cl_2 with m-chloroperbenzoic acid (MCPBA) and 28% H_2O_2 at room temperature gave Se-phenyl 2-[(benzimidazol-1-yl)methyl]selenobenzoate 8a. Similarly, the oxidation of sulfone 7a in THF with aqueous Oxone at room temperature gave the same selenolester 8a. The formation of selenolesters 8 can be explained by assuming either the involvement of oxaseleniranium cation 13, having a sulfinate group at C-2 of benzimidazole moiety, as an intermediate which is believed to be formed by an intramolecular nucleophilic attack of the polarized oxygen of the Se=O bond of selenoxide 6 to the #alpha#-carbon next to the sulfonyl group, or Pummerer-type reactions.