Abstract
Palladium-catalyzed asymmetric allylic substitution, due to its valuable reactive profile, has become a quite useful tool in organic synthesis fields. In the present study, density functional theory (DFT) calculations were applied to investigate the important factors for palladium-catalyzed 3-butene-2-ol and methylaniline amination reaction, with tetrahydrofuran (THF) as solvent. We find that this catalytic protocol results in high regio- and stereoselectivity, which is in line with the experimental result. According to our calculations, the high regio- and stereoselectivity is caused by the steric hindrance between the substrate and the catalyst ligand. To verify this point, we further explore the reactive process with different axial chirality on the catalyst ligand (altering the steric hindrance), and the results suggest that the preponderant R chiral configuration product has reversed. These results could lead to a better understanding of the mechanism for 3-butene-2-ol amination reaction and are helpful for the design of the corresponding catalyst ligand in the industry.
Highlights
The N-alkylation of amines is an important kind of organic synthetic reaction
The Gibbs free energy with thermal correction was obtained from the frequency calculations, and the single-point energies were performed on BP86 level with an all-atom def2-TZVP basis set (Weigend et al, 2003), empirical dispersion corrections (DFT-D3), and polarizable continuum model (PCM) method for THF solvent
According to our computational results, the high regio- and stereoselectivity of the catalyst could influence the reactive route of the reaction, which induces different preponderant chiral product
Summary
The N-alkylation of amines is an important kind of organic synthetic reaction. The products of such reactions relate to many important fields such as defense, chemical, and pharmaceutical. Alcohol has drawn more and more attention because it has equal characters with the aryl halide in N-alkylation reactions (Trost and Crawley, 2003; Lu and Ma, 2008; Zhang et al, 2014) This reactive profile has many advantages: the raw reactants are cheap to obtain, the yield and the selectivity are considerable, and the only. In 2014, Banerjee and co-workers chose Pd(dba) as catalyst to catalyze the 2-cyclohexene-1-ol and aniline amination reaction; they tested and optimized a series of reactive conditions (including ligands, additive, solvent, and temperature). They found that the yield was nearly 100% and the e.r. was 96:4–85:15 with L8 as the ligand, and 298K and tetrahydrofuran (THF) as the solvent (Banerjee et al, 2014). The results will demonstrate the preferred formation of the chiral product and reveal the cause of the high regio- and stereoselectivity
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