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1.
Catalytic enantioselective hydrogenation of prochiral vinylmetallic reagents can provide an attractive alternative to hydrometalation and bismetalation of alkenes. In this contribution, the first highly enantioselective hydrogenation of vinyl boronic esters is described. The chiral reduction products are versatile intermediates for chemical synthesis. 相似文献
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Several imine species comprising N-sulfinyl and N-sulfonyl ketimine, oxime, and enamine derivatives were subjected to asymmetric transfer hydrogenation in an azeotropic mixture of formic acid/triethylamine. Among them, the Rh-catalyzed transfer hydrogenation of N-sulfonyl ketimine afforded the corresponding 1-arylalkylamines in excellent yield and with high enantioselectivity. 相似文献
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Sergey E. Lyubimov Vadim A. Davankov Lyudmila N. Popova Petr M. Valetskii 《Journal of organometallic chemistry》2006,691(26):5980-5983
Novel chiral monodentate phosphite ligands bearing cymantrene fragment have been prepared. Phosphite 4 with PPh3, instead of CO-ligand, in cymantrene moiety provided higher enantioselectivity than its unsubstituted analogue 3 in hydrogenation of (Z)-methyl-2-acetamido-3-phenylacrylate. 相似文献
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Enabled by the broad scope of the Pd-catalyzed asymmetric alkylation of meso- and d,l-divinylethylene carbonate, several chiral diene ligands were prepared in two steps from commercial materials. Subsequently, these ligands were evaluated in the Rh-catalyzed asymmetric conjugate addition of boronic acids to enones. 相似文献
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Zheng-Chao Duan Xiang-Ping Hu Jun Deng Sai-Bo Yu Dao-Yong Wang Zhuo Zheng 《Tetrahedron: Asymmetry》2009,20(5):588-592
The first Rh-catalyzed enantioselective hydrogenation of dimethyl 2-methyleneglutarate and its derivatives has been reported. For the hydrogenation of dimethyl 2-methyleneglutarate with a chiral ferrocene-based monodentate phosphoramidite ligand (FAPhos), good enantioselectivity (over 90% ee) with full conversions was achieved. In contrast, the hydrogenation of substrates bearing an aryl substituent at a methylene moiety proved to be more difficult, in which the best enantioselectivity of up to 81% ee was obtained by the use of a P-stereogenic BoPhoz-type ligand. 相似文献
9.
Enantioselective Rh-catalyzed hydrogenation of vinyl carboxylates with monodentate phosphite ligands
[reaction: see text] Alkyl-substituted vinylcarboxylates, which normally show poor enantioselectivity in Rh-catalyzed hydrogenation with traditional chiral diphosphines, undergo highly enantioselective reactions with BINOL- and carbohydrate-based monophosphite ligands. 相似文献
10.
A series of chiral beta-aryl-gamma-amino acid ester derivatives were synthesized in high enantioselectivities (93-97% ee) via the Rh-catalyzed asymmetric hydrogenation of gamma-phthalimido-alpha,beta-unsaturated carboxylic acid esters using highly modular chiral BoPhoz-type phosphine-aminophosphine ligands. The method has been applied successfully to the synthesis of several chiral pharmaceuticals including (R)-baclofen and (R)-rolipram with high enantioselectivities. 相似文献
11.
Glasspoole BW Ghozati K Moir JW Crudden CM 《Chemical communications (Cambridge, England)》2012,48(9):1230-1232
Palladium-catalyzed cross-coupling reactions of secondary allylic boronic esters with iodoarenes were demonstrated under the conditions previously described for the coupling of benzylic substrates. The regioselectivity of the process was largely dictated by the pattern of olefin substitution. 相似文献
12.
A new family of readily available, recoverable and soluble polymer-monophosphite ligands were prepared and successfully used in the Rh-catalyzed asymmetric hydrogenation of enamides and beta-dehydroamino acid esters, in which up to 99 and 99.9% ee were obtained, respectively. 相似文献
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An improved process for the preparation of (E)-vinylboronic esters via a Zr-mediated hydroboration of alkynes, especially oxygen-containing alkynes, is described. 相似文献
14.
Panella L Aleixandre AM Kruidhof GJ Robertus J Feringa BL de Vries JG Minnaard AJ 《The Journal of organic chemistry》2006,71(5):2026-2036
Enantioselectivities up to >99% ee were achieved in the rhodium-catalyzed asymmetric hydrogenation of N-formyl dehydroamino esters using monodentate phosphoramidites as chiral ligands. The substrates were synthesized by condensation of methyl isocyanoacetate with a range of aldehydes and with cyclohexanone. A highly convenient multigram scale one step synthesis of methyl 2-(formamido)acrylate was developed. This compound was used in the synthesis of methyl 2-(formamido)cinnamate via a solvent free Heck reaction. Moreover, full conversion and >99% ee were obtained in 1 h in the hydrogenation of methyl 2-(formamido)acrylate with 0.2 mol % catalyst and 2 bar hydrogen pressure. The versatility of the formyl protection was established by its removal under mild conditions. 相似文献
15.
A new class of efficient catalysts was developed for the asymmetric hydrogenation of alpha,beta-unsaturated carboxylic acid derivatives by synthesizing a series of novel phosphine-phosphite ligands (4a-d) derived from readily available D-(+)-xylose. Excellent enantioselectivities (> 99%) were achieved under very mild reaction conditions (1 bar H(2) and 20 degrees C). Varying the biphenyl substituents in the phosphite moiety greatly affected the enantioselectivity in the hydrogenation reactions. The results also indicate that the sense of enantioselectivity is mainly controlled by the configuration of the phosphite moiety. (31)P[(1)H] NMR and kinetic studies on intermediates of the catalytic cycle show that the [Rh(P(1)-P(2))(enamide)]BF(4) species is the resting state and that the rate dependence is first order in rhodium and hydrogen pressure and zero order in enamide concentration. 相似文献
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A new methodology involving the copper(I)-catalyzed enantioselective conjugate reduction of β-boronyl-β-alkyl enoates was developed. Various chiral secondary boronate derivatives can be accessed in excellent yields and good to high levels of enantioselectivity through this efficient copper-catalyzed process using polymethylhydrosiloxane (PMHS) as hydride source. 相似文献
17.
《Tetrahedron: Asymmetry》2005,16(22):3640-3649
New electron-rich chiral 1,3-diphosphines of the BDPP type were prepared from 1,3-diphenylpropane-1,3-diol by an economically feasible synthetic approach. The σ-donor properties of the phosphines were determined by measurement of J(31P–77Se) coupling constants in the corresponding phosphine selenides. For comparison related, but electronically different, 1,3-diphosphines were considered. The new diphosphines showed good enantioselectivities as ligands in the Rh-catalyzed enantioselective hydrogenation of benchmark substrates and β-amino acid precursors (up to 98% ee). The electronic effects on the outcome of the enantioselective catalysis have been analyzed. 相似文献
18.
[formula: see text] Deprotonation of enantiopure (R,R)-1,2-dicyclohexyl-1,2-ethanediol 1-chloro-4-cyanobutylboronates 5 with LDA followed by treatment with anhydrous magnesium bromide yields (R)-(trans-2-cyanocyclobutyl)boronic esters 7 in high diastereomeric and enantiomeric purity. No cyclobutane formation has been observed in the absence of at least a catalytic amount of magnesium halide. 相似文献
19.
《Tetrahedron: Asymmetry》2005,16(6):1233-1238
A series of new H8-BINOL-derived unsymmetrical hybrid ferrocenylphosphine-phosphoramidite ligands have been synthesized and successfully used in Rh-catalyzed asymmetric hydrogenations. The same or higher enantioselectivities (99.9% ee) were achieved in the hydrogenation of dimethyl itaconate and α-dehydroamino acid esters as those obtained with BINOL-derived analogues. However, slightly lower enantioselectivities (99.0% ee) were obtained in the hydrogenation of enamides. 相似文献
20.
《中国化学快报》2022,33(12):5092-5095
Highly enantioselective Rh-catalyzed partial hydrogenation of unprotected simple 2-alkyl-5-aryl-disubstituted pyrroles has been successfully developed, generating a series of chiral 1-pyrroline derivatives generally with excellent results (95%–99% yields, 91%–96% ee). Moreover, 2,5-aryl-1H-pyrroles were hydrogenated well in high yields and good enantioselectivities. This efficient protocol features easily accessible substrates, wide substrate scope, well functional group compatibility, commercially available rhodium precursor and chiral ligand. It provides a versatile route to access chiral 1-pyrroline derivatives that are of great importance in organic synthesis and pharmaceutical chemistry. 相似文献