Quinone-Initiated Photocatalytic Enantioselective Giese Radical Addition with Ethers, Thioethers, Amines, and Alkanes

Photocatalytic
enantioselective Giese radical addition with inert
C(sp3)–H bonds represents a highly efficient and
economically favorable approach to synthesizing diverse value-added
chiral molecules from abundant feedstock. Herein, we disclose a quinone-initiated
photocatalytic asymmetric Giese radical addition of α-substituted
acrylamides with inert C(sp3)–H bonds by applying
simple quinones as HAT photocatalysts in combination with a chiral N,N′-dioxide/praseodymium(III) catalyst.
A wide array of ethers, thioethers, selenide, amines, and alkanes
can smoothly transform into the corresponding chiral α-aryl
amide derivatives with satisfactory enantioselectivities (68 examples,
up to 95% ee) under mild conditions. Based on spectroscopy studies
and control experiments, a quinone-initiated HAT catalytic cycle was
proposed, and DFT calculations revealed that the interaction between
quinone and chiral Lewis acid was essential for enantio-induction
in the asymmetric back hydrogen atom transfer process.