Metal complex catalyzed reactions of anils. II. Transimination

The exchange of aromatic residues between anilines and anils (transimination) has been shown to be efficiently catalyzed by metal complexes of thiourea. This reaction can be conveniently studied by nmr spin saturation transfer techniques. Experiments of this type using both CW and FT nmr spectrometers are reported. The rate of the reaction is about two orders of magnitude greater than the rates of reactions involving anil formation and hydrolysis with the same substrates and catalysts. The effectiveness of the catalysts vary in the same manner as they do for anil formation and the reaction is similarly subject to inhibition by competing ligands. The rate of exchange of the two inequivalent methyl groups in acetone anils is similarly catalyzed and may be studied by spin saturation transfer experiments. The lifetime of an anil molecule for methyl group exchange is approximately twice that for transimination suggesting that the rate determining process for transimination results in free rotation about the C—N bond so that the methyl groups have an equal probability of retaining or exchanging their environments.