Copper-Photocatalyzed Selective 1,6-Thiosulfonylation of Alkenes via 1,5-Hydrogen Atom Transfer.

There are substantial difficulties in constructing universal, selective access towards alkene remote thiosulfonylation relying on classic synthetic pathways. In this work, a photocatalytic copper-catalyzed protocol has been devised for the mild regioselective thionification of remote aliphatic C-H bonds and modular anti-Markovnikov alkene sulfonylation. The transformation hinges on activation of thiosulfonates by the BINAP-Cu(I) catalyst to form sulfonyl radicals and a subsequent 1,5-HAT that furnishes transposed alkyl radicals. A broad spectrum of alkenes and thiosulfonates exhibited good compatibility and furnished remote 1,6-thiosulfonylation products with an isolated yield up to 94%. Mechanistic probes further reveal that the transformation proceeds via single electron transfer rather than energy transfer. Moreover, this transformation is scalable to gram scale, and the resulting compounds are well suited for application in subsequent synthetic derivatization.