Synthesis of novel C2-symmetric chiral bis(oxazoline) ligands and their application in the enantioselective addition of diethylzinc to aldehydes

Asymmetric Henry Reaction Using Cobalt Complexes with Bisoxazoline Ligands Bearing Two Fluorous Tags

The effect of the presence of fluorous tags in bisoxazoline ligands on the stereoselectivity of the cobalt-catalyzed asymmetric Henry reaction was investigated. In contrast to the stereoselectivity obtained with conventional nonfluorous ligands, using bisoxazoline bidentate ligands featuring two fluorous tags in adjacent positions on the aromatic ring yielded a reversed stereoselectivity. The stereoselectivity also reversed when the fluorous tags were replaced with alkyl chains of equivalent length, albeit to a considerably lesser degree, highlighting the effect of the fluorous tags.

Asymmetric synthesis of an antagonist of neurokinin receptors: SSR 241586

SSR 241586 is a 2,2-disubstituted morpholine, developed by Sanofi-Aventis, which is active in the treatment of schizophrenia and irritable bowel syndrome (IBS). Different strategies have been studied to synthesize this molecule and among the strategies an organo-catalyzed Henry reaction, applied to an α-keto ester, has produced SSR 241586 in excellent enantiomeric excess.

Novel Polymer-Supported Chiral Catalysts for the Asymmetric Addition of Diethylzinc to Aldehydes

Newly synthesized polymer-supported chiral amino alcohol catalysts 5a and 5b have been proved to be effective for the enantioselective addition of diethylzinc to aldehydes, affording the corresponding sec-alcohols in moderate enantiomeric excesses with good to excellent yields. The recycled catalyst could be reused in the same reaction without significant deterioration in performance.

Enantioselective nitroaldol reaction of alpha-ketoesters catalyzed by cinchona alkaloids

The development of highly enantioselective and general catalytic nitroaldol (Henry) reactions with ketones is a challenging yet desirable task in organic synthesis. In this communication, we report an asymmetric nitroaldol reaction with alpha-ketoesters catalyzed by a new C6'-OH cinchona alkaloid catalyst. This is the first highly efficient organocatalytic asymmetric Henry reaction with ketones. This reaction is operationally simple and affords high enantioselectivity as well as good to excellent yield for a broad range of alpha-ketoesters.

Asymmetric Henry Reaction Catalyzed by C2-Symmetric Tridentate Bis(oxazoline) and Bis(thiazoline) Complexes: Metal-Controlled Reversal of Enantioselectivity

[reaction: see text] C(2)-symmetric tridentate bis(oxazoline) and bis(thiazoline) ligands with a diphenylamine backbone have been investigated in the catalytic asymmetric Henry reaction of alpha-keto esters with different Lewis acids. Their Cu(OTf)(2) complexes furnished S enantiomers, while Et(2)Zn complexes afforded R enantiomers, both of them with higher enantioselectivities (up to 85% ee). Reversal of enantioselectivity in asymmetric Henry reactions was achieved with the same chiral ligand by changing the Lewis acid center from Cu(II) to Zn(II). The results show that the NH group in C(2)-symmetric tridentate chiral ligands plays a very important role in controlling both the yields and enantiofacial selectivity of the Henry products.

Synthesis of newN-sulfonylated amino alcohols and application to the enantioselective addition of diethylzinc to aldehydes

A series of N-sulfonylated amino alcohols were prepared and the enantioselective addition of diethylzinc to aldehydes catalyzed by titanium(IV) complexes of those ligands were carried out. Excellent enantioselectivities were obtained for the desired alcohols with enantiomeric excess values up to 94% of R-configuration.