Asymmetric Michael–aldol tandem cyclization of ω-oxo-α,β-unsaturated esters with 10-mercaptoisoborneol methyl ether
摘要:
The asymmetric reaction of omega-oxo-alpha,beta-unsaturated esters with lithium chiral thiolates afforded the Michael-aldol tandem cyclization products in high yield and good stereo selectivity. Reductive desulfurization gave the corresponding optically pure 2-hydroxycycloalkanecarboxylates. (C) 2003 Elsevier Science Ltd. All rights reserved.
New Class of Chiral Diphosphine Ligands for Highly Efficient Transition Metal-Catalyzed Stereoselective Reactions: The Bis(diphenylphosphino) Five-membered Biheteroaryls
esters and in the hydrogenation of olefinic substrates. The optical and chemical yields were comparable with those reported for the same Ru(II)-binap-catalyzed reactions carried out under the same experimental conditions. The 2,2'-bis(diphenylphosphino)-3,3'-bibenzo[b]furan (1c), the oxygenated analogue of bitianp, was found to be configurationally unstable at room temperature. Complete structural X-ray
Sprouted green peas have been used for the first time as biocatalysts for enantioselective reduction of prochiral ketones. The reactions are highly enantioselective to furnish chiral alcohols in good yields. The sprouted peas as biocatalysts are a cheap and easy way for generating some interesting chiral alcohols. This process is efficient and convenient to produce chiral secondary alcohols in water.
search for green chemistry methods for the enantioselective reduction of ketoesters Saccharomyces cerevisiae- and ruthenium-catalyzed reactions in water have been investigated. The highest enantiomeric excesses for the reduction of α- and β-ketoesters have been obtained by S. cerevisiae. Chiral ruthenium catalysts are active for the reduction of all ketoesters with low to moderate enantioselectivities
Stereo- and chemoselective transfer hydrogenation of carbonyl groups with RuCl2(PPh3)3 and BINAP-Ru as catalysts and Et3NH+H2PO2−·1,5H2O as a hydrogen donor
作者:Bui The Khai、Antonio Arcelli
DOI:10.1016/0040-4039(96)01476-1
日期:1996.9
Using Et3NH+H2PO2−.1.5 H2O as a hydrogendonor, the RuCl2(Ph3P)3, and BINAP-Ru proved highly active catalysts for transferhydrogenation of ketones under milder conditions than other hydrogendonors. 2-Methyl-, 2-chloro-, 2-(ethoxy-carbonyl)cyclohexanones and -cyclopentanones were reduced to the less stable axial alcohols in excellent diastereoisomeric excess (de: 90–100%), and the carbonylgroup of α
Homogeneous and heterogeneous asymmetric reactions. Part 5. Diastereoselective and enantioselective hydrogenation of cyclic β-keto esters on modified<i>Raney</i>-nickel catalysts
作者:Gyula Wittmann、György Göndös、Mihály Bartók
DOI:10.1002/hlca.19900730312
日期:1990.5.2
significantly. The hydrogenations of β-ketoesters 1 and 3 proceed with an enantioselectivity of 10–15% on the modified catalysts, while the similar hydrogenation of 5 yields optically inactive 6. The (1S,2R)-enantiomers of the cis-isomers of 2 and 4 are formed in larger quantity, whereas the (lR,2R)-enantiomers of the corresponding trans-isomers predominate (Scheme 1). The enantioselective formation of
甲基-2- oxoeyclopentanecarboxylate(的氢化1),乙基2- oxocyelohexanecarboxylate(3),和2-甲基环己酮(5上未修饰的)阮内-Ni催化剂引线主要到的形成CIS的羟基非对映体2,4,和6,分别(方案2)。在手性酒石酸((R,R)-C 4 H 6 O 6 / Raney -Ni和(R,R)-C修饰的催化剂上的不对称氢化4 H 6 O 6 / NaBr / Raney -Ni),顺式异构体的优势显着增加。在改性催化剂上,β-酮酸酯1和3的氢化反应对映选择性为10-15%,而类似的5氢化则产生光学惰性6。2和4的顺式异构体的(1 S,2 R)-对映体大量形成,而相应反式的(1 R,2 R)-对映体形成-异构体占主导(方案1)。的对映选择性形成反式- 2和反式- 4可以解释主要是在环状β酮酯通过酮形式的不对称氢化的方面,而相应的顺式-羟基酯前进通过烯醇形式。