Chiral Diphosphonites as Ligands in the Ruthenium-Catalyzed Enantioselective Reduction of Ketones, B-Ketoesters and Ketimines
申请人:Reetz Manfred T.
公开号:US20080255355A1
公开(公告)日:2008-10-16
Chiral ruthenium complexes are disclosed, obtained by reaction of a ruthenium salt with a chiral diphosphonite. Chiral diols with the general structure given in scheme
1
are preferably used as chiral diphosphonites. Said ruthenium complexes can be simply and economically obtained and provide high enantioselectivity on reduction of ketones, β-ketoesters and ketimines.
diphosphine ClickFerrophos ligands (CF), based on a triazoleferrocene backbone, was synthesized in a four-step sequence via click chemistry methodology. In addition to the four previously synthesized ligands CF1, CF4, CF7 and CF10, six novel CF ligands CF2–3 and CF5–8 were prepared. Hydrogenation reactions of alkenes and ketones were significantly improved upon by using CF ligands as rhodium- or ruthenium-complexes
ClickFerrophos: New Chiral Ferrocenyl Phosphine Ligands Synthesized by Click Chemistry and the Use of Their Metal Complexes as Catalysts for Asymmetric Hydrogenation and Allylic Substitution
were readily prepared in four steps using Click Chemistry methodology, starting from the commercially available aminoferrocene 1. Rhodium and ruthenium complexes of ClickFerrophos 5 were effective catalysts for the hydrogenation of alkenes and ketones, respectively, producing products with up to 99.7% ee. The analogous palladium complex with 6 worked well for asymmetric allylic alkylation.
A new family of ferrocenylphosphane ligands has been prepared. Their flexible synthesis allows many structural modifications. The asymmetric induction of these ligands was examined in the hydrogenation of functionalized C=C, C=O, and C=N bonds. The enantioselectivity of the reaction was strongly dependent on the substituent R at the position alpha to the ferrocene moiety. In many cases, both enantiomeric
Stereoselective reduction of thiocarbonyl compounds with baker's yeast
作者:Jens Kaergaard Nielsen、Jergen Øgaard Madsen
DOI:10.1016/s0957-4166(00)86212-6
日期:1994.3
2-octanethione have been reduced with baker'syeast to give optically active thiols. The reductions parallel those of the oxygen analogues with respect to rate and diastereo- and enantioselectivity but, generally, the enantiomeric excess (ee) values are smaller. The influence of experimental variables such as substrate concentration, physiological condition of the yeast (resting/fermenting, fresh/dry/frozen)