Theoretical study of Ni(0)-catalyzed intermolecular hydroamination of branched 1,3-dienes: reaction mechanism, regioselectivity, enantioselectivity, and prediction of the ligand.

Abstract

Nickel-catalyzed hydroamination of dienes with phenylmethanamines was studied theoretically to investigate reaction mechanism. These calculated results revealed that Ni-catalyzed hydroamination began with the O - H bond activation of trifluoroethanol, including three important elementary steps: the ligand-to-ligand hydrogen migration, the nucleophilic attack of phenylmethanamine, and hydrogen migration. The nucleophilic attack of phenylmethanamine was the rate-determining step, and the branched product of 3,4-addition with (S)-chirality was the most dominant. The N - H bond activation of phenylmethanamine occurred more difficultly than the O - H bond of trifluoroethanol, because of high ΔG and ΔG≠. In addition, the origin of regioselectivity and enantioselectivity, and prediction of the ligand were also discussed in this text. All computations were performed with Gaussian09 program. All geometries were optimized at the ωB97XD/6-31G(d,p) level (SDD for Ni), and to obtain more accurate potential energy, single-point calculation was carried out at the ωB97XD/cc-pVDZ level (SDD for Ni). The Cramer-Truhlar continuum solvation model (SMD) was used to evaluate solvation effect of mesitylene, and a correction of the translational entropy was made with the procedure of Whitesides group.