for α,β-disubstituted α,β-unsaturated esters is performed via three general and robust reaction sequences: (i) Ti−Claisen condensation (formylation) of esters to give α-formyl esters (12 examples, 60−99%), (ii) (E)- and (Z)-stereocomplementary enol p-toluenesulfonylation (tosylation) using TsCl−N-methylimidazole (NMI)−Et3N and LiOH (24 examples, 82−99%), and (iii) stereoretentive Suzuki−Miyaura cross-coupling
Overcoming Electron Bias in Hydroarylation of Phenylpropiolic Acid Derivatives To Enable Highly Reversed Regio- and Stereoselectivity via Steric and Transient Post Addition Coordination
phenylpropiolic acidderivatives are compatible with this hydroarylation protocol, offering an alternative selectivity to traditional β-syn-hydroarylation reactions. The distinct advantages of our method include precise control over selectivity, reduced catalyst loading, and broad tolerance toward functional groups. These features highlight the potential of our approach in the synthesis of multifunctionalized
Reactions of chlorine substituted (E)-2,3-diphenylpropenoic acids over cinchonidine-modified Pd: Enantioselective hydrogenation versus hydrodechlorination
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.
Garay, Raul O.; Cadaleiro, Mercedes C., Journal of Chemical Research, Miniprint, 1988, # 12, p. 2962 - 2971
作者:Garay, Raul O.、Cadaleiro, Mercedes C.
DOI:——
日期:——
HALTON, B.;MAIDMENT, A. I.;OFFICER, D. L.;WARNES, J. M., AUSTRAL. J. CHEM., 1984, 37, N 10, 2119-2128
作者:HALTON, B.、MAIDMENT, A. I.、OFFICER, D. L.、WARNES, J. M.