A Phenyliodonium Ylide as a Precursor for Dicarboethoxycarbene:  Demonstration of a Strategy for Carbene Generation

Thermal or photochemical decomposition of carbene precursors, especially diazocompounds and diazirenes, leads in many cases to both a free carbene intermediate and products formed directly from the precursor. This ability of precursors to mimic carbenes often complicates mechanistic studies. For example,direct photolysis of dimethyl diazomalonate leads to products stemming from reactions of substrate with1:C(CO2Me)2,3:C(CO2-Me)2, and photoexcited1a(11a*) as outlined in Scheme 1. In situations such as this, alternative modes of carbene generation have proved valuable in characterizing the reactive species. Here we describe a strategy for identifying new carbene precursors and report the facile generation of 1:C(CO2Et)2by thermal decomposition of iodonium ylide, as well as a supporting computational study.