- Synergistic Relay Reactions To Achieve Redox-Neutral α-Alkylations of Olefinic Alcohols with Ruthenium(II) Catalysis
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Herein, we report a ruthenium-catalyzed redox-neutral α-alkylation of unsaturated alcohols based on a synergistic relay process involving olefin isomerization (chain walking) and umpolung hydrazone addition, which takes advantage of the interaction between the two rather inefficient individual reaction steps to enable an efficient overall process. This transformation shows the compatibility of hydrazone-type “carbanions” and active protons in a one-pot reaction, and at the same time achieves the first Grignard-type nucleophilic addition using olefinic alcohols as latent carbonyl groups, providing a higher yield of the corresponding secondary alcohol than the classical hydrazone addition to aldehydes does. A broad scope of unsaturated alcohols and hydrazones, including some complex structures, can be successfully employed in this reaction, which shows the versatility of this approach and its suitability as an alternative, efficient means for the generation of secondary and tertiary alcohols.
- Kan, Jian,Li, Chao-Jun,Li, Chen-Chen,Li, Jianbin,Lv, Leiyang,Qiu, Zihang
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supporting information
p. 4544 - 4549
(2020/02/04)
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- ALTERNATE PROCESSES FOR THE PREPARATION OF PYRROLIDINE DERIVATIVES
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Aspects of the present application relate to process for the preparation of Pyrrolidine derivatives useful as key intermediates for active ingredients. Specific aspects relate to alternate process for the preparation of Upadacitinib intermediate, 4-ethylpyrrolidine-3-carboxylic acid, its ester or a salt thereof. Processes disclosed here in are cost effective and industrially viable as compared to known processes.
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Page/Page column 32
(2019/02/06)
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- Stabilization of cobalt catalysts by embedment for efficient production of valeric biofuel
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We herein report, for the first time, a bifunctional base-metal catalyst (Co@HZSM-5) that acts as an efficient alternative to noble-metal catalysts (e.g., Pt, Ru) for the conversion of levulinic acid into valeric biofuel under batch and fixed-bed reactor conditions. The cobalt nanoparticles were embedded in HZSM-5 crystals and catalyzed the sequential hydrogenations of the ketone and alkene functional groups; meanwhile, the acidic zeolite catalyzed the ring opening of the γ-valerolactone intermediate. Although base metals (e.g., Co) are abundant and inexpensive, their sintering and/or leaching under liquid-phase conditions always lead to the irreversible deactivation of the catalyst. In this system, the embedment structure stabilizes the nanoparticles, and Co@HZSM-5 could be used up to eight times. This work provides a practical clue toward the stabilization of base-metal catalysts and will inspire the development of large-scale biorefinery.
- Sun, Peng,Gao, Guang,Zhao, Zelun,Xia, Chungu,Li, Fuwei
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p. 4136 - 4142
(2015/02/19)
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- Preparations of 4-substituted 3-carboxypyrazoles
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The scopes of three synthetic methods reported for the preparation of an array of 3-pyrazolecarboxylates featuring substituents on position 4 were investigated. The first one is based on the potassium permanganate oxidation of methylpyrazoles. The second starts with the condensation between DMF dimethylacetal and ethyl pyruvate and is followed by the addition of hydrazine hydrochloride. The last one makes use of the cycloaddition of diazomethane on acrylate esters followed by a bromine-based oxidative rearrangement into 4-substituted 3-pyrazole esters.
- Janin, Yves L.
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p. 1410 - 1414
(2014/01/06)
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- Radical mechanism in the elimination of 2-arylsulfinyl esters
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The mechanism of the dehydrosulfenylation of 2-arylsulfinyl esters was investigated. The reaction was found to follow a homolytic cleavage mechanism as verified by electrospray ionization tandem mass spectrometry and experimental work. Rearranged sulfoxides are obtained as byproduct during the elimination reaction.
- Latorre, Antonio,Lopez, Irakusne,Ramirez, Victoria,Rodriguez, Santiago,Izquierdo, Javier,Gonzalez, Florenci V.,Vicent, Cristian
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experimental part
p. 5191 - 5197
(2012/07/27)
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- Synthesis and biological evaluation of 3-substituted-indolin-2-one derivatives containing chloropyrrole moieties
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Eighteen novel 3-substituted-indolin-2-ones containing chloropyrroles were synthesized and their biological activities were evaluated. The presence of a chlorine atom on the pyrrole ring was crucial to reduce cardiotoxicity. The presence of a 2-(ethylamino) ethylcarbamoyl group as a substituent at the C-4' position of the pyrrole enhanced the antitumor activities notably. IC 50 values as low as 0.32, 0.67, 1.19 and 1.22 μM were achieved against non-small cell lung cancer (A549), oral epithelial (KB), melanoma (K111) and large cell lung cancer cell lines (NCI-H460), respectively.
- Jin, Yun-Zhou,Fu, Da-Xu,Ma, Nan,Li, Zhan-Cheng,Liu, Quan-Hai,Xiao, Lin,Zhang, Rong-Hua
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experimental part
p. 9368 - 9385
(2012/01/05)
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- Expanded scope of synthetic bacteriochlorins via improved acid catalysis conditions and diverse dihydrodipyrrin-acetals
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(Chemical Equation Presented) Bacteriochlorins are attractive candidates for a wide variety of photochemical studies owing to their strong absorption in the near-infrared spectral region. The prior acid-catalysis conditions [BF 3 · O(Et)2 in CH3CN at room temperature] for self-condensation of a dihydrodipyrrin-acetal (bearing a geminal dimethyl group in the pyrroline ring) typically afforded a mixture of three macrocycles: the expected 5-methoxybacteriochlorin (MeOBC-type), a 5-unsubstituted bacteriochlorin (HBC-type), and a free base B,D-tetradehydrocorrin (TDC-type). Here, a broad survey of >20 acids identified four promising acid catalysis conditions of which TMSOTf/2,6-di-tert-butylpyridine in CH2Cl 2 at room temperature was most attractive owing to formation of the 5-methoxybacteriochlorin as the sole macrocycle regardless of the pyrrolic substituents in the dihydrodipyrrin-acetal (electron-withdrawing, electron-donating, or no substituent). Eleven new dihydrodipyrrin-acetals were prepared following standard routes. Application of the new acid catalysis conditions has afforded diverse bacteriochlorins (e.g., bearing alkyl/ester, aryl/ester, diester, and no substituents) in a few days from commercially available starting materials. Consideration of the synthetic steps and yields for formation of the dihydrodipyrrin-acetal and bacteriochlorin underpins evaluation of synthetic plans for early installation of bacteriochlorin substituents via the dihydrodipyrrin-acetal versus late installation via derivatization of β-bromobacteriochlorins. Treatment of the 5-methoxybacteriochlorins with NBS gave regioselective 15-bromination when no pyrrolic substituents were present or when each pyrrole contained two substituents; on the other hand, the presence of a β-ethoxycarbonyl group caused loss of regioselectivity. The 15 new bacteriochlorins prepared herein exhibit a long-wavelength absorption band in the range 707-759 nm, providing tunable access to the near-infrared region. Taken together, this study expands the scope of available bacteriochlorins for fundamental studies and diverse applications. 2010 American Chemical Society.
- Krayer, Michael,Ptaszek, Marcin,Kim, Han-Je,Meneely, Kelly R.,Fan, Dazhong,Secor, Kristen,Lindsey, Jonathan S.
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experimental part
p. 1016 - 1039
(2010/04/04)
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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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- Base-Catalyzed Reactions of α,β-Unsaturated Esters and Nitriles. 4. Dimerization of β-Alkyl-Substituted Acrylates
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2-Butenoates 1-C4 alkyl, cyclohexyl, or 1-bornyl> and higher β-alkyl-substituted acrylates 2-C9 n-alkyl> undergo highly selective (>95percent) dimerization in the presence of promoted potassium or sodium catalysts to yield corresponding 2-alkylidene-3-alkylglutarates (3).The reaction involves metalation of the β-alkylacrylate at the C-2 position, followed by addition at C-3 of a second monomeric molecule.Changes in the relative extent of dimerization (Kr) as a function of structural and experimentalvariables were determined.Kr is strongly dependent upon the inductive and steric characteristics of the alcoholic (R) group and of the β-alkyl substituent (R').For an n-alkyl group as R' the Kr value increases with increase in chain length from C1 to C4 but then decreases for longer substituents (C5-C9).Among the two geometric isomers in the dimeric product 3, the isomer with an α-vinylic hydrogen cis to the carboalkoxy group is predominant in all cases, but its relative concetration decreases with an increase in the size of R'.Branched or cyclic β-substituents in 2 prevent dimerization due to steric hindrance in the rate-determining addition step.Promoted potassium or sodium catalysts show much higher dimerization activity compared to supported alkali metals or to alkoxides.For conversions of up to 60percent, Kr values in proton-exchanging alkylbenzene solvents and in nonexchanging alkylcyclohexanes are closely similar, indicating faster abstraction of an α-vinylic hydrogen from the monomer, rather than a benzylic hydrogen from the solvent, in the chain regeneration step of the reaction.
- Shabtai, Joseph,Ney-Igner, Eva
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p. 3795 - 3802
(2007/10/02)
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