Fragmentary reports exist concerning transition metal-catalyzed air oxidations(l,2) or dehydrogenations of primary smines(J,4) or secondary amines(5).
None of these results suggest that the catalytic systems are effective for oxidations of tertiary amines. In fact, Ralandin and Vasyunina(5) were able to dehydrogenate a primary amine function in the presence of a tertiary function without altering the tertiary amine functional group. Most of the results reported involved vigorous conditions, e.g., 320-400' (3,4,5) or in refluxing xylene(2), though one example(l) involved reactions at ambient temperatures.
We have now discovered that platinum is an effective catalyst for the molecular oxygen oxidation of N-methyl groups in tertiary amines to give N-formyl groups. The reaction is remarkably selective, inasmuch as N-benzyl groups or N-ethyl groups in tertiary amines are not similarly attacked. Furthermore, the oxidations occur at ambient temperatures, requiring only stirring of the platinum catalyst with the amine in a solvent. Clean yields of N-formyl compounds are obtained, with evidence of only -trace quantities of side-products (by vapor phase chromatography).
The general equation is indicated in eq (1).