Photocatalytic aerobic α-thiolation/annulation of carbonyls with mercaptobenzimidazoles

A concise aerobic photocatalysis using a blue LED combined with a Lewis acid has been developed to enable alpha-thiolation/annulation of carbonyls. Inexpensive, nontoxic Rose Bengal was demonstrated as the best catalyst. Hence, this transition-metal-free protocol allows mild Csp(3)-S couplings with both ketones and aliphatic aldehydes with a range of compatible useful functionalities.