- Iridium-Catalyzed Amidation of in Situ Prepared Silyl Ketene Acetals to Access α-Amino Esters
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Disclosed herein is a convenient Ir-catalyzed amidation of esters to access α-amido esters. Initially prepared silyl ketene acetals are directly employed, without separate purification, for subsequent amidation with an oxycarbonylnitrenoid precursor using the Cp*(LX)Ir(III) catalyst. The α-amidation was facile for both α-aryl and α-alkyl esters. Density functional theory studies revealed that the generation of a putative Ir-nitrenoid is facilitated by the chelation of the countercation additive during the N-O bond cleavage of the nitrene precursor.
- Chang, Sukbok,Gwon, Yunyeong,Kim, Dongwook,Lee, Minhan
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p. 1088 - 1093
(2022/02/10)
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- Tandem Insertion/[3,3]-Sigmatropic Rearrangement Involving the Formation of Silyl Ketene Acetals by Insertion of Rhodium Carbenes into S-Si Bonds
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Allyl 2-diazo-2-phenylacetates are shown to react with trimethylsilyl thioethers in the presence of rhodium(II) catalysts to generate α-allyl-α-thio silyl esters. The transformation involves a tandem process involving formal rhodium-catalyzed insertion of the carbene group into the S-Si bond to generate a silyl ketene acetal, followed by a spontaneous Ireland-Claisen rearrangement. The silyl ester products were isolated as the corresponding carboxylic acids after aqueous workup. Intramolecular cyclopropanation of the allyl fragment generally competes with addition of the heteroatom to the carbene center. The reaction occurs under mild conditions and in high yield, allowing for rapid entry into rearrangement tetrasubstituted products. Propargyl esters were shown to generate the corresponding α-allenyl products.
- Combs, Jason R.,Lai, Yin-Chu,Van Vranken, David L.
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supporting information
p. 2841 - 2845
(2021/05/05)
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- Enantioselective Copper-Catalyzed Radical Ring-Opening Cyanation of Cyclopropanols and Cyclopropanone Acetals
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A novel approach for enantioselective cyanation of cyclopropanols and their derivatives through copper-catalyzed radical relay processes has been developed. Various cyclopropanols and cyclopropanone acetals are compatible to the catalytic conditions, providing β-carbonyl nitriles with excellent enantioselectivity. These products can be readily converted to chiral γ-amino acids derivatives and drugs such as (R)-baclofen. Preliminary mechanistic studies have supported a ring-opening process for cyclopropanoxy radicals followed by copper-catalyzed enantioselective cyanation of benzylic radicals to form the C?CN bonds in an enantioselective manner. (Figure presented.).
- Chen, Pinghong,Guo, Yin-Long,Liu, Guosheng,Wang, Lei,Wu, Lianqian
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supporting information
p. 2189 - 2194
(2020/04/17)
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- Methylphenidate, right pai methyl ester preparation method, intermediate and preparation method
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The invention discloses preparation methods of methylphenidate and dexmethylphenidate, intermediates and preparation methods of the intermediates. The invention provides the preparation method of the methylphenidate, wherein the preparation method is any one of the following methods: a first method comprises the following steps of in a solvent, carrying out an amino protecting group removal reaction of a compound 4 with an amino de-protection reagent, and thus obtaining the methylphenidate 5; a second method comprises the following steps of under the action of an alkali, carrying out an intramolecular nucleophilic substitution reaction of a compound 11 to obtain the methylphenidate 5; and a third method comprises the following steps of in a closed system, in a solvent, under a palladium on carbon or palladium carbon hydroxide catalytic condition, carrying out a reaction of a compound 9 with hydrogen, to obtain the methylphenidate 5. The synthesis method has the advantages of short steps, cheap and easily obtained raw materials, high product yield, good chiral purity, low production cost, and good atomic economy, and is suitable for industrialized production.
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Paragraph 0313-0318
(2019/04/30)
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- Coupling Reaction of Enol Derivatives with Silyl Ketene Acetals Catalyzed by Gallium Trihalides
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A cross-coupling reaction between enol derivatives and silyl ketene acetals catalyzed by GaBr3took place to give the corresponding α-alkenyl esters. GaBr3showed the most effective catalytic ability, whereas other metal salts such as BF3?OEt2, AlCl3, PdCl2, and lanthanide triflates were not effective. Various types of enol ethers and vinyl carboxylates as enol derivatives are amenable to this coupling. The scope of the reaction with silyl ketene acetals was also broad. We successfully observed an alkylgallium intermediate by using NMR spectroscopy, suggesting a mechanism involving anti-carbogallation among GaBr3, an enol derivative, and a silyl ketene acetal, followed by syn-β-alkoxy elimination from the alkylgallium. Based on kinetic studies, the turnover-limiting step of the reaction using a vinyl ether and a vinyl carboxylate involved syn-β-alkoxy elimination and anti-carbogallation, respectively. Therefore, the leaving group had a significant effect on the progress of the reaction. Theoretical calculations analysis suggest that the moderate Lewis acidity of gallium would contribute to a flexible conformational change of the alkylgallium intermediate and to the cleavage of the carbon?oxygen bond in the β-alkoxy elimination process, which is the turnover-limiting step in the reaction between a vinyl ether and a silyl ketene acetal.
- Nishimoto, Yoshihiro,Kita, Yuji,Ueda, Hiroki,Imaoka, Hiroto,Chiba, Kouji,Yasuda, Makoto,Baba, Akio
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supporting information
p. 11837 - 11845
(2016/08/05)
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- Synthesis of 3-pyrrolin-2-ones by rhodium-catalyzed transannulation of 1-sulfonyl-1,2,3-triazole with ketene silyl acetal
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α-Imino rhodium carbenoids generated from 1-sulfonyl 1,2,3-triazole were applied to the 3 + 2 cycloaddition with ketene silyl acetal, offering a novel and straightforward synthesis of biologically interesting compound 3-pyrrolin-2-one with broad substrate scope.
- Ran, Rui-Qiao,He, Jun,Xiu, Shi-Dong,Wang, Kai-Bing,Li, Chuan-Ying
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supporting information
p. 3704 - 3707
(2014/08/05)
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- Direct use of esters in the Mukaiyama aldol reaction: A powerful and convenient alternative to aldehydes
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An indium triiodide catalyst promoted the direct transformation from esters to β-hydroxycarbonyl compounds using hydrosilanes and silyl enolates by a one-stage process. Various esters were applicable, and the high chemoselectivity of this system brings compatibility to many functional groups: alkenyl, alkynyl, chloro, and hydroxy.
- Inamoto, Yoshihiro,Nishimoto, Yoshihiro,Yasuda, Makoto,Baba, Akio
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supporting information; experimental part
p. 1168 - 1171
(2012/04/04)
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- Gallium tribromide catalyzed coupling reaction of alkenyl ethers with ketene silyl acetals
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A 'Ga'llant couple: The α-alkenylation of esters was accomplished by GaBr3-catalyzed coupling between alkenyl ethers and ketene silyl acetals. In this reaction system, various alkenyl ethers, including those with vinyl and substituted alkenyl groups, were applicable, and the scope of applicable ketene silyl acetals was sufficiently broad. The mechanism is also discussed. Copyright
- Nishimoto, Yoshihiro,Ueda, Hiroki,Yasuda, Makoto,Baba, Akio
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supporting information; experimental part
p. 8073 - 8076
(2012/08/29)
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- CoMFA, synthesis, and pharmacological evaluation of (E)-3-(2-carboxy-2- arylvinyl)-4,6-dichloro-1H-indole-2-carboxylic acids: 3-[2-(3-Aminophenyl)-2- carboxyvinyl]-4,6-dichloro-1H-indole-2-carboxylic acid, a potent selective glycine-site NMDA receptor antagonist
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(E)-3-(2-Carboxy-2-phenylvinyl)-4,6-dichloro-1H-indole-2-carboxylic acid, 1, is a potent and selective antagonist of the glycine site of the N-methyl-D-aspartate (NMDA) receptor. Using 3D comparative molecular field analysis (CoMFA) to guide the synthetic effort, a series of aryl diacid analogues of 1 were synthesized to optimize in vivo potency, duration of action, and binding activity. It was found that the incorporation of a substituted aromatic with an electron withdrawing group or a heterocyclic group at the 2-position of the 3-propenyl moiety of 1 gave compounds with better affinity and potency in the murine stroke model. Ultimately this led to the discovery of 3-[2-(3-aminophenyl)-2-carboxyvinyl]-4,6-dichloro-1H-indole-2-carboxylic acid, 19, as a new potent selective glycine-site NMDA receptor antagonist.
- Baron, Bruce M.,Cregge, Robert J.,Farr, Robert A.,Friedrich, Dirk,Gross, Raymond S.,Harrison, Boyd L.,Janowick, David A.,Matthews, Donald,McCloskey, Timothy C.,Meikrantz, Scott,Nyce, Philip L.,Vaz, Roy,Metz, William A.
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p. 995 - 1018
(2007/10/03)
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- Synthesis and isolation of α-oxo sulfines
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The synthesis of several α-oxo sulfines is discribed. Various α-oxo sulfines can be isolated as such. The Diels-Alder reaction of these sulfines with 1,3-dienes can be catalyzed by Lewis acids.
- Damen, Theodorus J. G.,Zwanenburg, Binne
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p. 319 - 320
(2007/10/03)
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- 3-(indol-3-yl)-propenoic acid derivatives and pharmaceutical compositions thereof
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The present invention is new 3-(indol-3-yl)-propenoic acid derivatives and pharmaceutical compositions thereof. These new 3-indolyl-3-yl-prpopenoic acid derivatives are useful as NMDA antagonist.
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- ETUDE DE LA REACTION CHLOROCARBENE-ACETALS DE CETENES. I. SYNTHESE D'ESTERS α,β-ETHYLENIQUES.
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The reaction of chloro, chloromethyl and chlorophenyl carbenoids with ketene alkylsilylacetals has been studied.Excellent yields of cyclopropanation were observed and the unstable chlorocyclopropanone acetals formed were thermally rearranged in high yield into α-substituted α,β-ethylenic esters.This new method for the synthesis of unsaturated esters appeared complementary of the known-ones.
- Slougui, N.,Rousseau, G.
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p. 2643 - 2652
(2007/10/02)
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- 1,3-Dithienium- and 1,3-Dithiolenium Salts, III. Synthesis of Cyclic Dithioacetals of β-Keto Esters from Ketene Silyl Acetals
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The 1,3-dithian-2-ylium tetrafluoroborates 3, available by different methods, react in good yields with the ketene silyl acetals 2 to give the new cyclic dithioacetals 4 which are deacetalized to the β-keto esters 5 and 9.
- Stahl, Ingfried
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p. 3159 - 3165
(2007/10/02)
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- Reaction of Ketene Silyl Acetals with Diazonium Salts: a Novel α-Amino Acid Ester Synthesis
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The reaction of ketene silyl acetals with arenediazonium tetrafluoroborate gave α-hydrazono and α-azo esters, which were easily hydrogenated to α-amino esters.
- Sakakura, Toshiyasu,Tanaka, Masato
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p. 1309 - 1310
(2007/10/02)
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