Photoredox mediated nickel catalyzed C(sp)-H thiocarbonylation of ethers.

The first direct C(sp)-H thiocarbonylation reaction is achieved by visible light photoredox/Ni dual catalysis. The thioester group of thiobenzoate is transferred to the α-oxy carbon of various cyclic/acyclic ethers, which is the opposite to the commonly expected chemical reactivity involving acyl group transfer the weaker C(acyl)-S activation. Through mechanistic studies, we proposed that the reaction is initiated by photocatalytic reduction and fragmentation of the thioester into an acyl radical and a thiolate. A nickel complex binds to the thiolate and induces the decarbonylation of the acyl radical to form an aryl radical, which abstracts hydrogen from the α-oxy carbon of the ether. The resulting α-oxy C(sp) centered radical re-binds to the (RS)(CO)Ni complex, which undergoes CO migratory insertion and reductive elimination to give the desired thioester product.