Oxidative coupling of carbon monoxide and amines catalyzed by cuprous complexes

Abstract

Carbon monoxide co-ordinated to cuprous amine complexes has been found to be much more susceptible to oxidation by certain oxidants (cupric complexes, nitrobenzene, methylene blue) than carbon monoxide in the free state. This phenomenon underlies Cu(I)-catalyzed oxidative coupling reactions of CO and certain amines at ambient temperature and pressure, leading to ureas: 2R₁R₂NH + CO + 2Cu(II)complex [graphic omitted] R₁R₂N—[graphic omitted]—NR₁R₂+2H⁺+2Cu(I) complex.

If oxygen is used for the re-oxidation of Cu(I), the Cu(I)–Cu(II)-catalyzed reaction assumes the following stoichiometry: 2R₁R₂NH + CO +½O₂→ R₁R₂N—[graphic omitted]—NR₁R₂+H₂O.

In all reactions of this type the cyclic sec-amine ligands piperidine and morpholine form exceptionally reactive copper complexes. The mechanism of the reactions, which is only partially understood, is discussed.