[5,5]-Sigmatropic Rearrangement of Aryl Sulfoxides with α,β-Unsaturated Nitriles

Herein, we report the [5,5]-rearrangement of aryl sulfoxides with readily available α,β-unsaturated nitriles, furnishing γ-aryl α,β-unsaturated nitriles with excellent regioselectivity. This transformation proceeds under mild reaction conditions and exhibits high chemo- and regioselectivity, excellent functional-group compatibility, and a broad substrate scope. Notably, no ortho-cyanoalkylated products arising from competing [3,3]-rearrangements were detected. Interestingly, mechanistic investigations elucidate the crucial role of tropinone, which acts both as a Lewis base in its Mannich-type addition to the in situ-generated α,β-unsaturated sulfonium imine species and as a Bronsted base in promoting γ-deprotonation of LB-addition sulfonium imine species to form the rearrangement precursor.