Asymmetric Catalytic Synthesis of Allylic Sulfenamides from Vinyl α-Diazo Compounds by a Rearrangement Route

The asymmetric rearrangement of allylic sulfilimines is an effective route to synthetically attractive targets, such as allylic sulfenamides. The current methods are limited to chirality transfer from chiral allylic sulfilimine precursors. Herein, we report a general and fundamentally new rearrangement route to access optically enriched allylic sulfenamides and their derivatives. The process involves S-alkylation and an unusual S-to-N rearrangement step. A chiral nickel complex enables the transformation of a broad scope of sulfenamides and vinyl α-diazo pyrazoleamides under mild conditions. Various allylic sulfenamides have been synthesized with excellent γ-regioselectivity and enantioselectivity, and can be efficiently converted into sulfinamide and 4-aminobutenoic acid derivatives. In addition, DFT calculations demonstrate the connection between the spin state and conformation of the nickel vinyl carbenoid, as well as an unknown rearrangement process.