A density functional theory study of the enantioselective reduction of prochiral ketones promoted by chiral spiroborate esters

Abstract

ABSTRACT:Recently, chiral spiroborate ester [(R)-2-((1,3,2-dioxaborolan-2-yloxy)methyl)pyrrolidine] has been experimentally employed as an effective chiral catalyst in the borane-mediated asymmetric reduction of prochiral ketones to produce the corresponding secondary alcohols. In this article, we have theoretically investigated the mechanism of the reduction using density functional theory. The results reveal that this reaction is accomplished via four steps. Fully geometry optimized reactants, products, transition states, and intermediates were obtained at the B3LYP/6-31G (d, p) level. The analysis of these results reveals one pathway that is more energetically favorable, and its associated geometries correlate well with the final products of the reaction. The further calculations show that the solvent effect of THF has no great influence on enantioselectivity of this reduction.

A DFT study of the enantioselective reduction of oxime ethers promoted by chiral spiroborate esters

“…3) are −27.14 and −24.92 kcal/mol lower than the energy of the reactants, indicating that the hydrogen transfer from B3 to C6 is exothermic. Moreover, the energy barriers for the reverse reactions (from M2(r) and M2(s) to TS2(r) and TS2(s) ) may reach up to 38.29 and 33.07 kcal/mol, which are so high that the hydrogen transfer steps are thermodynamically irreversible at room temperature [35, 36]. In addition, the C6 atom has become the chiral center after this process, so we believe this step should be the stereoselctivity‐determining step.…”

Theoretical Investigations toward the Asymmetric Insertion Reaction of Diazoester with Aldehyde Catalyzed by N-Protonated Chiral Oxazaborolidine: Mechanisms and Stereoselectivity

“…The geometrical optimizations of the reactants, transition states, intermediates, and products in all the possible reaction pathways were carried out using the gradient-corrected function of Becke and of Lee, Yang, and Parr (B3LYP) − for exchange and correction, with the standard 6-31G­(d, p) basis set as implemented in Gaussian 09 . The selected functional method has been confirmed to be proper for the CBS catalytic system − and other theoretical investigations. − Solvation by propionitrile was taken into account for all calculations (optimizations and frequencies) by a relatively simple self-consistent reaction field (SCRF) method, which is based on the integral equation formalism polarizable continuum model (IEF-PCM). , In the procedure, the solvent is assimilated as a continuous medium, characterized by the dielectric constant (ε = 27.7), which surrounds a molecule-shape cavity in which the solute is placed. Most significant structures had been represented in the figures by using CYLView…”

A DFT study on the competing mechanisms of PPh3-catalyzed [3+3] and [3+2] annulations between 5-acetoxypenta-2,3-dienoate and 1C,3O-bisnucleophiles

“…The reaction mechanisms were studied using the density functional theory (DFT), which has been widely used in the study of the organic and enzymatic reaction mechanisms [63][64][65][66][67][68][69][70][71][72][73].…”