Photocatalytic N-formylation of amines via a reductive quenching cycle in the presence of air.

Photochemical N-formylation of amines was performed under simple and mild reaction conditions. Amines are common electron donors in reductive photocatalysis, which then typically decompose after donating an electron to the photocatalyst. We have found that these oxidized amines can be utilized to give N-formamides in the presence of air without additional formylating agents. The reaction proceeds via the in situ formation of enamines. Oxygen (air) is necessary for the reaction to occur as it regenerates the photocatalyst forming superoxide radical anions as crucial intermediates involved in the reaction.