Copper Mediated C(sp2)–H Sulfonylation of Aldehydes using a Catalytic Transient Imine Directing Group

The copper mediated β–C(sp2)–H sulfonylation of benzaldehydes with sulfinate salts is accomplished using β-alanine as a catalytic transient directing group. A broad range of sulfonylated benzaldehydes are prepared us-ing copper fluoride as both copper source and oxidant. Both b-(ortho) and g-(peri)-sulfonylation are demon-strated. Mechanistic studies indicate the turnover limiting step to be a concerted asynchronous C–H cleavage via a Wheland-type transition state.