Eosin†Y as a Direct Hydrogen-Atom Transfer Photocatalyst for the Functionalization of C-H Bonds.

Eosin Y, a well-known economical alternative to metal catalysts in visible-light-driven single-electron transfer-based organic transformations, can behave as an effective direct hydrogen-atom transfer catalyst for C-H activation. Using the alkylation of C-H bonds with electron-deficient alkenes as a model study revealed an extremely broad substrate scope, enabling easy access to a variety of important synthons. This eosin Y-based photocatalytic hydrogen-atom transfer strategy is promising for diverse functionalization of a wide range of native C-H bonds in a green and sustainable manner.

Photoinduced Nickel-Catalyzed Chemo- and Regioselective Hydroalkylation of Internal Alkynes with Ether and Amide α-Hetero C(sp3)-H Bonds.

A direct hydroalkylation of disubstituted alkynes with unfunctionalized ethers and amides was achieved in an atom-efficient and additive-free manner through the synergistic combination of photoredox and nickel catalysis. The protocol was effective with a wide range of internal alkynes, providing products in a highly selective fashion. Notably, the observed regioselectivity is complementary to conventional radical addition processes. Mechanistic investigations suggest that the photoexcited iridium catalyst facilitated the nickel activation via single-electron transfer.