Discovery and mechanistic study of Al(III)-catalyzed transamidation of tertiary amides.

Cleavage of the C-N bond of carboxamides generally requires harsh conditions. This study reveals that tris(amido)Al(III) catalysts, such as Al2(NMe2)6, promote facile equilibrium-controlled transamidation of tertiary carboxamides with secondary amines. The mechanism of these reactions was investigated by kinetic, spectroscopic, and density functional theory (DFT) computational methods.

TiIV-mediated reactions between primary amines and secondary carboxamides: amidine formation versus transamidation.

Titanium(IV)-mediated reactions between primary amines and secondary carboxamides exhibit different outcomes, amidine formation versus transamidation, depending on the identity of the TiIV complex used and the reaction conditions employed. The present study probes the origin of this divergent behavior. We find that stoichiometric TiIV, either Cp*TiIV complexes or Ti(NMe2)4, promotes formation of amidine and oxotitanium products.

Mechanism of Al(III)-catalyzed transamidation of unactivated secondary carboxamides.

The carbon-nitrogen bond of secondary carboxamides is generally thermodynamically and kinetically unreactive; however, we recently discovered that the trisamidoaluminum(III) dimer Al2(NMe2)6 catalyzes facile transamidation between simple secondary carboxamides and primary amines under moderate conditions. The present report describes kinetic and spectroscopic studies that illuminate the mechanism of this unusual transformation. The catalytic reaction exhibits a bimolecular rate law with a first-order dependence on the Al(III) and amine concentrations.

Double C-H activation during functionalization of phenyl(methyl)ketene on iridium(I) using alkynes. synthesis of 1,4-dien-3-ones.

Under the influence of an Ir(I) metal fragment, the methyl group of phenyl(methyl)ketene undergoes two C-H activations in reacting with internal alkynes, giving metallacycles 3 in 86-94% yield. Treatment of 3 with CO liberates 1,4-dien-3-ones 5 in 81-93% yield, along with CO complex 4. A possible mechanism for the very selective double C-H activation-alkyne coupling is discussed.