Organic Small Molecule Catalytic Asymmetric Reaction Theory

Recently, the organocatalysis became one of the most powerful methods in the asymmetric catalytic fields. Direct asymmetric reactions catalyzed by the metal-free catalysts have made considerable developments, no matter in the experiment or industry. While, the mechanism of catalytic reations and the origin of stereoseletivity could only do preliminary speculate by scientists. So we could make use of the present theoretical study to provide a good explainaton. Quantum mechanic calculations were employed to study the direct Aldol reaction, Mannich reation and asymmetric hydrogenation.First, in the asymmetric aldol reaction, we studied the stereoselectivities in the direct anti-and syn-Aldol reactions between a-fluoro (chloro) ketones and 4-nitrobenzaldehyde catalyzed by different amino acid derivatives. The calculated results provide a good explanation for the opposite syn versus and diastereoselectivities of these two kinds of catalysts; Second, we investigated the direct anti-Mannich reactions catalyzed by chiral 3-trifluoromethanesulfonamido- pyrrolidine and explained the origin of the stereoselectivities in the a-and (3-amino acids catalyzed Mannich reactions involving cyclohexanone (anti-selectivity for theβ-amino acids,syn-selectivity for the a-amino acids); Finally, in the asymmetric hydrogenation, using Hantzsch esters as the hydrogen source, the organic amine and different acid as a total catalyst, we explained the mechanism of this catalyst could reduce the conjugate C-C bonds involvingα,β-unsaturated carbonyl compounds as the donors.