Reactions of chlorine substituted (E)-2,3-diphenylpropenoic acids over cinchonidine-modified Pd: Enantioselective hydrogenation versus hydrodechlorination
摘要:
The effect of the chlorine position on the C-Cl bond hydrogenolysis and the enantioselective hydrogenation of Cl substituted (E)-2,3-diphenylpropenoic acid derivatives has been studied over cinchonidine-modified Pd/Al2O3. In contrast to the fast hydrodechlorination of the beta-phenyl-para-Cl substituted acids the Cl on the alpha-phenyl ring was barely hydrogenolized. These observations were interpreted by the different arrangements of the two phenyl rings on the surface, with the alpha- and beta-phenyl rings adsorbed tilted and parallel, respectively. The results confirmed the beneficial effect of the alpha-phenyl-ortho-substituents on the chiral discrimination, thus the 2,3-diphenylpropionic acids substituted by Cl on the alpha-phenyl ring could be prepared in good yields and optical purities. The conclusions were used for the rational design of an acid, i.e. (E)-2-(2-methoxyphenyl)-3-(3,4-difluorophenyl)propenoic acid, which afforded the best optical purity (ee up to 95% at 295 K) described until now in this heterogeneous system. (C) 2010 Elsevier B.V. All rights reserved.
Copper-Catalyzed Carboxylation of Hydroborated Disubstituted Alkenes and Terminal Alkynes with Cesium Fluoride
作者:Martin Juhl、Simon L. R. Laursen、Yuxing Huang、Dennis U. Nielsen、Kim Daasbjerg、Troels Skrydstrup
DOI:10.1021/acscatal.6b03571
日期:2017.2.3
A protocol for the hydrocarboxylation of disubstituted alkenes and terminal alkynes providing access to different secondary carboxylicacids and malonic acid derivatives has been developed. This methodology relies on an initial hydroboration using 9-BBN followed by carboxylation with carbondioxide in the presence of a coppercatalyst and the additive, cesium fluoride. Different cyclohexene, styrene
A weakly carboxylate-directed palladium(II)-catalyzed ortho-C–H alkynylation of diverse phenylacetic acids promoted by monoprotected amino acid ligand enabled is reported. The reaction has a broad substrate scope including α-secondary, tertiary, and quaternary phenylacetic acids. Notably, the direct ortho-C–H alkynylation of α-quaternary phenylacetic acids and chiral α-tertiary phenylacetic acids was
NOVEL PYRIDINE DERIVATIVES AS SPHINGOSINE 1-PHOSPHATE (S1P) RECEPTOR MODULATORS
申请人:ALLERGAN, INC.
公开号:EP2646027B1
公开(公告)日:2014-10-15
Kit for automated resolving agent selection and method thereof
申请人:Vaidya A. Niteen
公开号:US20070185346A1
公开(公告)日:2007-08-09
The present invention concerns an improved method and a tray or kit, which is useful to select quickly the optimum resolution agents, combinations and conditions to separate optical isomers. The tray of 24, 48, 96 or more samples is examined simultaneously visually or by standard analytical techniques.