Хиральные комплексы переходных металлов с хелатными азотными лигандами в асимметрическом гидрировании с переносом водорода

Abstract

The reaction of catalytic hydrogenation involving hydrogen transfer through unsaturated C = C and C = O bonds in organic compounds in the presence of optically active soluble complexes of transition metals with nitrogen-containing multidentate ligands has recently gained increased popularity. This review is aimed at generalising available information on the most effective and promising metal complex catalysts for asymmetric hydrogenation involving hydrogen transfer, which have been proposed in the past 10–15 years. Since the activity and selectivity of catalysts based on transition metal complexes are largely dependent on their composition and structure, the design of ligands, the presence or absence of stereogenic centres, the stability and configuration of the chelating ligand system, the nature of the dentate atoms present therein are extremely important. Researchers worldwide have been largely focused on the synthesis and use such ligands, as optically active diamines and aminoalcohols with sp3 -hybridized dentate atoms. These compositions are not oxidized in the coordination sphere of transition metals compared to phosphine ligands, at the same time as maintaining a high level of stereogenicity. Optically active ligands with sp2 nitrogen atoms containing the C = N azomethine bond and oxazoline fragments have been considered as a separate group. In complexes with transition metals, these ligands exhibit a high stability in the catalytic hydrogenation reaction with hydrogen transfer. The stereoselectivity of catalysts in some cases increases with an increase in the denticity of nitrogen-containing ligands. Among them are N-heterocyclic N, H, C–ligands in the Rh (III) complexes; Ru (II) complexes with tridentate N, N, N–ligands with chiral oxazoline fragments; C, N, N–ruthenium complexes. In this review, we grouped catalysts by ligand denticity (from 2 to 6). Comparative data on the activity of various catalysts and the stereoselectivity of respective reactions is provided. The effect of the structure of chiral ligands on the catalytic characteristics of metal complexes is discussed. The authors declare no conflict of interests regarding the publication of this article.