Direct cross-coupling between alkenes/R-H or alkenes/RXH is a dream reaction, especially without external oxidants. Inputting energy by photocatalysis and employing a cobalt catalyst as a two-electron acceptor, a direct C-H/X-H cross-coupling with H evolution has been achieved for C-O and C-N bond formation. A new radical alkenylation using alkene as the redox compound is presented. A wide range of aliphatic alcohols-even long chain alcohols-are tolerated well in this system, providing a new route to multi-substituted enol ether derivatives using simple alkenes. Additionally, this protocol can also be used for N-vinylazole synthesis. Mechanistic insights reveal that the cobalt catalyst oxidizes the photocatalyst to revive the photocatalytic cycle.

In this work, a direct C-H activation of thiophenes was presented via an oxidation pathway under visible-light irradiation, in which the thiophene radical cation serves as the key intermediate. Various thiophenes and azoles could be transformed into the corresponding amination products well, and HO was the only byproduct which is environmentally benign. Our results showed that tert-butyl nitrite (TBN) served as the electron transfer mediator and O as the terminal oxidant to regenerate the photocatalyst DDQ and revive the photocatalytic cycle.

Ring-opening iodination or bromination of unstrained cycloalkanols with NaI or NaBr and PhI(OAc)2 under visible light irradiation is developed.