Triplet Ketone Catalysis-Enabled Functionalization of Thioanisoles with Maleimides

Considering the importance of sulfur-containing organic molecules in various domains of chemistry, we report herein a protocol for the catalytic diastereoselective synthesis of tricyclic heterocycles through α-C(sp³)-H functionalization of thioanisoles with maleimides enabled by triplet ketone catalysis. Mild reaction conditions, an inexpensive photocatalyst, molecular oxygen as a terminal oxidant, and compatibility with various functional groups are advantages of the protocol. Preliminary mechanistic studies suggest the generation of α-thioalkyl radicals and involvement of aerial oxygen in our reaction conditions.