Cooperative Photocatalysis of 9,10‐Phenanthrenequinone and Sn(OTf) ₂ for Direct Mannich Reaction of Ethers via Hydrogen Atom Transfer Pathway

A dual photocatalytic system combining 9,10‐phenanthrenequinone ( o ‐PQ) and Sn(OTf) 2 enabled the visible light‐induced Mannich‐type addition of ethers to nitrones via direct Csp 3 –H activation. This oxidant‐ and reductant‐free method featured broad substrate scope, good yields, and excellent functional group tolerance. Gram‐scale synthesis and downstream transformations (Suzuki, Sonogashira, Heck) demonstrated its synthetic utility. Mechanistic studies suggested a cooperative cycle where a photoexcited o ‐PQ‐Sn(II) complex mediated hydrogen atom transfer, generating α ‐oxy radicals that reacted with Sn(II)‐activated nitrones.