Photocatalytical aerobic α-thiolation/annulation of carbonyls with mercaptobenzimidazoles

A concise aerobic photocatalysis by blue LED combined with Lewis acid has been developed to enable α-thiolation/annulation of carbonyls. Inexpensive, nontoxic Rose Bengal was demonstrated as the best catalyst. Hence, this transition-metal-free protocol allows mild Csp3−S couplings with both ketones and aliphatic aldehydes with a range of useful functionalities compatible.