Unexpected Role of p-Toluenesulfonylmethyl Isocyanide as a Sulfonylating Agent in Reactions with α-Bromocarbonyl Compounds.

The reactions of p-toluenesulfonylmethyl isocyanide (TosMIC) with α-bromocarbonyl compounds leading efficiently to α-sulfonated ketones, esters, and amides were reported, in which an explicit new role of TosMIC as the sulfonylating agent was uncovered for the first time. Mechanistic study by control experiments and DFT calculations suggested that the reaction is initiated by Cu(OTf)2-catalyzed hydration of TosMIC to form a formamide intermediate, which undergoes facile C–S bond cleavage under the mediation of a Cs2CO3 additive.