Diarylformamides as a Safe Reservoir and Room Temperature Source of Ultra‐Pure CO in the Context of a ‘Green’ rWGS Reaction

Diphenylformamide 1 and bisformamide 9 are shown to be safe reservoirs and sources of CO. Their perfectly selective decarbonylations are achieved in solution at room temperature with potassium and cesium diarylamide catalysts. 1 is obtained in excellent yields directly from triethylammonium formate, which may be the product of CO2 scrubbing with NEt3 and catalytic hydrogenation. 1 thus represents a key intermediate in a low‐temperature rWGS reaction sequence. Moreover, solvent‐free decarbonylations of 1 may be run either in the melt at 70 °C or with 9 even in the solid state at 88 °C with improved atom economy. These simple and practical transition‐metal‐free decarbonylations afford ultra‐pure (i. e. dry and solvent‐free) CO at moderate temperatures and the diarylamines byproducts are recycled as pure compounds. In the absence of catalysts, diarylformamides 1 and 9 are long‐term stable at >200 °C. DFT‐calculations indicate a reaction pathway with a rate‐determining deprotonation of Ph2NC(O)H and barrier‐free CO elimination from Ph2NC(O)−. The solvent‐free catalytic decarbonylation of diarylformamides affords very pure CO and makes them ideal solid‐state reservoirs of CO. The recovered diarylamines are readily formylated with formic acid on 30–100 g scales.