A chiral ligand mediated aza-conjugate addition strategy for the enantioselective synthesis of β-amino esters that contain hydrogenolytically sensitive functionality
摘要:
Aza-conjugate addition of the lithium anion of N-trimethylsilyl-p-methoxybenzylamine to tert-butyl enoate acceptors, in the presence of a stoichiometric amount of enantiopure 1,2-dimethoxy-1,2-diphenylethane and excess trimethylsilyl chloride, affords tert-butyl-N-p-methoxybenzyl-beta-amino esters with excellent levels of enantiocontrol. These N-p-methoxybenzyl-beta-amino-esters may be deprotected under oxidative conditions via treatment with ceric ammonium nitrate, followed by acid hydrolysis of the resultant imine intermediates, to afford enantiopure beta-amino-esters containing hydrogenolytically sensitive functionality. (C) 2015 Elsevier Ltd. All rights reserved.
Palladium-catalyzed alkenation of thiophenes and furans by regioselective C–H bond functionalization
摘要:
A palladium-catalyzed direct alkenation of thiophenes and furans has been developed in the presence of AgOAc and pyridine. A variety of olefinic substrates such as acrylates, acrylamides, and acrylonitrile can perform the direct oxidative coupling reactions with various thiophenes and furans to give the mono-alkenylated products in good yields. In most cases, the (E)-isomers were isolated as the major products. (C) 2009 Elsevier Ltd. All rights reserved.
The bis-1,4-dimesityl-1,2,3-triazol-5-ylidene–palladium complex (1a) successfully catalyzes the Mizoroki–Heck and Sonogashira coupling reactions with aryl bromides to give the corresponding alkenes and alkynes, respectively, in good to excellent yields. In the Mizoroki–Heck reaction, electron-rich, electron-poor, and functionalized aryl bromides and alkenes are tolerated, while the substrates are limited
An inexpensive and highly stable ligand 1,4-bis(2-hydroxy-3,5-di-tert-butylbenzyl)piperazine for Mizoroki–Heck and room temperature Suzuki–Miyaura cross-coupling reactions
作者:Sasmita Mohanty、D. Suresh、Maravanji S. Balakrishna、Joel. T. Mague
DOI:10.1016/j.tet.2007.10.081
日期:2008.1
characterized. The palladium catalyst was formed by combination of 1 with [Cl2Pd(COD)] in a ratio of 1:1, tested in the Suzuki–Miyaura and Mizoroki–Heck cross-couplingreactions. Coupling of a variety of aryl bromides with phenylboronic acid using methanol as solvent at room temperature, or at 60 °C, gave generally high yields of coupled products. Coupling of aryl chlorides with organoboron reagent at
Catalytic Asymmetric Synthesis with Rh−Diene Complexes: 1,4-Addition of Arylboronic Acids to Unsaturated Esters
作者:Jean-François Paquin、Corey R. J. Stephenson、Christian Defieber、Erick M. Carreira
DOI:10.1021/ol051533l
日期:2005.8.1
route to enantioenriched tert-butyl 3,3-diarylpropanoates is presented. These useful building blocks are prepared via an asymmetricrhodium-catalyzedconjugateaddition of arylboronic acids to unsaturated tert-butyl esters in the presence of chiral dienes as ligands. The addition of both electron-poor and electron-rich boronic acids proceeds smoothly with various enoates in 63-90% yield with high enantioselectivites
Rhodium-Catalyzed Heck-Type Coupling of Boronic Acids with Activated Alkenes in an Aqueous Emulsion
作者:Mark Lautens、John Mancuso、Harpreet Grover
DOI:10.1055/s-2004-829161
日期:——
Intermolecular couplings between arylboronic acids and activated alkenes catalyzed by a water-soluble tert-butyl amphosrhodium complex were found to progress at room temperature and generated Heck-type products with high yields and excellent selectivity. Substitution on the alkene component encouraged the formation of products arising from a conjugate addition-protonation process. In the case of Heck
Wittig Reactions in Water Media Employing Stabilized Ylides with Aldehydes. Synthesis of α,β-Unsaturated Esters from Mixing Aldehydes, α-Bromoesters, and Ph<sub>3</sub>P in Aqueous NaHCO<sub>3</sub>
作者:Amer El-Batta、Changchun Jiang、Wen Zhao、Robert Anness、Andrew L. Cooksy、Mikael Bergdahl
DOI:10.1021/jo070665k
日期:2007.7.1
range of stabilized ylides and aldehydes. Despite sometimes poor solubility of the reactants, good chemical yields normally ranging from 80 to 98% and high E-selectivities (up to 99%) are achieved, and the rate of the reactions in water is unexpectedly accelerated. The efficiency of water as a medium in the Wittig reaction is compared to conventional organic solvents ranging from carbon tetrachloride