Easily assembled, modular N,O-chelating ligands for Ta(V) complexation: a comparative study of ligand effects in hydroaminoalkylation with N-methylaniline and 4-methoxy-N-methylaniline

The influence of structurally related N,O-chelating ligands with additional heteroatoms (N, O, P, S) on the reactivity of in situ generated tantalum complexes for the hydroaminoalkylation of amines has been explored. Reactivity was probed by evaluating the catalytic ability of these N,O-chelating systems with N-methylaniline and 4-methoxy-N-methylaniline substrates. Enhanced reactivity is observed with amide proligands bearing an ortho-methoxyphenyl group on the nitrogen. 4-Methoxy-N-methylaniline is found to be more prone to undergo C–H functionalization via hydroaminoalkylation than N-methylaniline. The use of the related substrate 2-methoxy-N-methylaniline is not tolerated, and instead C(sp3)–O bond cleavage was observed.