Hydrophosphination of CO₂ and Subsequent Formate Transfer in the 1,3,2-Diazaphospholene-Catalyzed N-Formylation of Amines

Hydrophosphination of CO₂ with 1,3,2-Diazaphospholene (NHP-H; 1) afforded phosphorus formate (NHP-OCOH; 2) through the formation of a bond between the electrophilic phosphorus atom in 1 and the oxygen atom from CO₂, along with hydride transfer to the carbon atom of CO₂. Transfer of the formate from 2 to Ph₂SiH₂ produced Ph₂Si(OCHO)₂ (3) in a reaction that could be carried out in a catalytic manner by using 5 mol % of 1. These elementary reactions were applied to the metal-free catalytic N-formylation of amine derivatives with CO₂ in one pot under ambient conditions.