Metal complex catalyzed reactions of anils. II. Transimination

Abstract

. Can. J. Chem. 55,2426Chem. 55, (1977. 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. [Traduit par le journal]

Neighboring Group Participation and Internal Catalysis Effects on Exchangeable Covalent Bonds: Application to the Thriving Field of Vitrimer Chemistry

“…The success of imines-derived vitrimers (Figure 26) may be explained by the versatility of this linkage, but also because these vitrimers can be reprocessed without the need for a catalyst. [163][164][165][166][167][168][169][170][171][172][173][174] When used in organic chemistry or biochemistry, transimination was reported to be catalysed by thiourea metal complexes (2 orders of magnitude rate acceleration), 177 triflate salts of scandium, terbium, samarium and other lanthanides (up to 5 orders of magnitude acceleration), 178,261 zinc bromide, 262 iron chloride, copper chloride and magnesium chloride. 263 Besides, acid and basic catalysis are known to be efficient as well, in aqueous 175,264 or organic solutions.…”

“…Therefore, the focus here is put on transimination, which requires residual amines, and on imine metathesis, which does not. Transimination has been known to occur through an equilibrated associative pathway for several decades. , Three successive steps were described. The first and rate-determining step consists in the attack of a free primary amine on the imine carbon atom to form a geminal diamine tetrahedral intermediate. ,− Then, two protons transfer from the nitrogen atom of the formerly attacking amino moiety to the nitrogen atom of the former imine moiety. ,, Finally the exchanged amino moiety dissociates and leads to the formation of the new imine (Scheme a).…”

Second sphere coordination of phenols, anilines, and benzoic acids to the hexacyanocobaltate(III) anion

“…The correlation coefficients for the final fit to eq. [3] are also given. They are generally greater than 0.99, indicating that this model gives a satisfactory fit to the data.…”

“…The linearity of the fit to eq. [3] indicates that self-association is not important. This fit does not, however, prove that only a 1: 1 complex is formed.…”

“…However, the intercept at zero concentration can be estimated fairly reliably and according to eq. [3] this provides a value of KAv, at extreme dilution, i.e. under conditions where the effects of dimerization are minimal.…”