The Experts below are selected from a list of 40026 Experts worldwide ranked by ideXlab platform
Shengyin Zhao - One of the best experts on this subject based on the ideXlab platform.
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regioselective hetero michael Addition of oxygen sulfur and nitrogen nucleophiles to maleimides catalyzed by bf3 oet2
ChemInform, 2015Co-Authors: Yunxia Deng, Wei Zhang, Shengyin ZhaoAbstract:The Addition of oxygen, nitrogen, and sulfur nucleophiles to maleimides catalyzed by boron trifluoride etherate is studied.
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regioselective hetero michael Addition of oxygen sulfur and nitrogen nucleophiles to maleimides catalyzed by bf3 oet2
Synthesis, 2015Co-Authors: Yunxia Deng, Wei Zhang, Shengyin ZhaoAbstract:A practical BF3·OEt2-catalyzed regioselective 1,2-Addition or 1,4-Hetero-Michael Addition of oxygen, sulfur, and nitrogen nucleophiles to maleimides has been developed for the synthesis of alkyl fumarate derivatives or 3-substituted succinimides, respectively. This reaction system has wide substrate scope and gives moderate to excellent yields (up to 96%) of the desired products. In contrast to the base-catalyzed methods, this strategy is very general, simple, environmentally friendly, and tolerant of oxygen.
Craig J Forsyth - One of the best experts on this subject based on the ideXlab platform.
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Synthesis of the C22–C40 Domain of the Azaspiracids
2016Co-Authors: Zhigao Zhang, Yong Chen, Daniel Adu-ampratwum, Antony Akura Okumu, Nathaniel T. Kenton, Craig J ForsythAbstract:An efficient synthesis of the C22–C40 domain of the azaspiracids is described. The synthetic route features a Nozaki–Hiyama–Kishi (NHK) coupling and chelation controlled Mukaiyama aldol reaction to access an acyclic intermediate and a double-intramolecular-Hetero-Michael Addition (DIHMA) to provide the FG-ring system bridged ketal
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antibodies with broad specificity to azaspiracids by use of synthetic haptens
Journal of the American Chemical Society, 2006Co-Authors: Craig J Forsyth, Son T Nguyen, Ingunn A Samdal, Lyn R Briggs, Thomas Rundberget, Morten Sandvik, Christopher O MilesAbstract:The development of general, sensitive, portable, and quantitative assays for the azaspiracid (AZA) class of marine toxins is urgently needed. Use of a synthetic hapten containing rings F-I of AZA to generate antibodies that cross-react with the AZAs via their common C28-C40 domain and use of these antibodies in ELISA and immunoaffinity columns are reported. This approach has many advantages over using intact azaspiracids (AZAs) derived from environmental samples or total synthesis as haptens for antibody development. A derivative of the levorotatory C28-C40 azaspiracid domain (1) was synthesized efficiently using a one-pot Staudinger reduction/intramolecular aza-Wittig reaction-imine capture sequence to form the H-I ring spiroaminal and a double intramolecluar Hetero-Michael Addition to assemble the F-G ring ketal. Conjugation of the hapten 1 to cBSA and immunization in sheep generated antibodies that recognized and bound to ovalbumin-conjugated 1 in the absence of AZA1. This binding was inhibited by 1 in a concentration-dependent manner. A mixture of AZA1, AZA2, AZA3, and AZA6 caused a degree of inhibition of antibody binding consistent with its total AZA content, rather than just its content of AZA1. This result suggests that the antibodies also have a similar affinity for AZA2, AZA3, and AZA6 as they do for AZA1 and that such antibodies are suitable for analysis of AZAs in shellfish samples.
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application of the double intramolecular hetero michael Addition dihma approach in spiroketal synthesis total synthesis of 4s 6s 4 hydroxy 1 7 dioxaspiro 5 5 undecane a dacus oleae olive fly pheromone
Tetrahedron Letters, 2002Co-Authors: Junliang Hao, Craig J ForsythAbstract:Application of a novel double intramolecular Hetero-Michael Addition (DIHMA) strategy to spiroketal synthesis was illustrated by a concise synthesis of (±)-(4S*,6S*)-4-hydroxy-1,7-dioxaspiro[5.5]undecane, a Dacus oleae olive fly pheromone.
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synthesis of a 2 9 dioxabicyclo 3 3 1 nonane via double intramolecular hetero michael Addition entry to the f g ring system of the azaspiracids
Organic Letters, 2001Co-Authors: Josep Aiguade, Junliang Hao, Craig J ForsythAbstract:An effective approach to form a 1,3-disubstituted 2,9-dioxabicyclo[3.3.1]nonane system representing the core of the F and G rings (C28−C34) of the azaspiracid natural products has been developed. The double intramolecular Hetero-Michael Addition (DIHMA) of a diol upon an ynone generated the bicyclic ketal in a highly diastereoselective fashion.
Yoshiji Takemoto - One of the best experts on this subject based on the ideXlab platform.
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mechanistic insight into asymmetric hetero michael Addition of α β unsaturated carboxylic acids catalyzed by multifunctional thioureas
Journal of the American Chemical Society, 2018Co-Authors: Noboru Hayama, Ryuta Kuramoto, Tamas Foldes, Kazuya Nishibayashi, Yusuke Kobayashi, Imre Papai, Yoshiji TakemotoAbstract:Carboxylic acids and their corresponding carboxylate anions are generally utilized as Bronsted acids/bases and oxygen nucleophiles in organic synthesis. However, a few asymmetric reactions have used carboxylic acids as electrophiles. Although chiral thioureas bearing both arylboronic acid and tertiary amine were found to promote the aza-Michael Addition of BnONH2 to α,β-unsaturated carboxylic acids with moderate to good enantioselectivities, the reaction mechanism remains to be clarified. Detailed investigation of the reaction using spectroscopic analysis and kinetic studies identified tetrahedral borate complexes, comprising two carboxylate anions, as reaction intermediates. We realized a dramatic improvement in product enantioselectivity with the Addition of 1 equiv of benzoic acid. In this aza-Michael reaction, the boronic acid not only activates the carboxylate ligand as a Lewis acid, together with the thiourea NH-protons, but also functions as a Bronsted base through a benzoyloxy anion to activate th...
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Mechanistic Insight into Asymmetric Hetero-Michael Addition of α,β-Unsaturated Carboxylic Acids Catalyzed by Multifunctional Thioureas
2018Co-Authors: Noboru Hayama, Ryuta Kuramoto, Kazuya Nishibayashi, Yusuke Kobayashi, Tamás Földes, Imre Pápai, Yoshiji TakemotoAbstract:Carboxylic acids and their corresponding carboxylate anions are generally utilized as Brønsted acids/bases and oxygen nucleophiles in organic synthesis. However, a few asymmetric reactions have used carboxylic acids as electrophiles. Although chiral thioureas bearing both arylboronic acid and tertiary amine were found to promote the aza-Michael Addition of BnONH2 to α,β-unsaturated carboxylic acids with moderate to good enantioselectivities, the reaction mechanism remains to be clarified. Detailed investigation of the reaction using spectroscopic analysis and kinetic studies identified tetrahedral borate complexes, comprising two carboxylate anions, as reaction intermediates. We realized a dramatic improvement in product enantioselectivity with the Addition of 1 equiv of benzoic acid. In this aza-Michael reaction, the boronic acid not only activates the carboxylate ligand as a Lewis acid, together with the thiourea NH-protons, but also functions as a Brønsted base through a benzoyloxy anion to activate the nucleophile. Moreover, molecular sieves were found to play an important role in generating the ternary borate complexes, which were crucial for obtaining high enantioselectivity as demonstrated by DFT calculations. We also designed a new thiourea catalyst for the intramolecular oxa-Michael Addition to suppress another catalytic pathway via a binary borate complex using steric hindrance between the catalyst and substrate. Finally, to demonstrate the synthetic versatility of both Hetero-Michael Additions, we used them to accomplish the asymmetric synthesis of key intermediates in pharmaceutically important molecules, including sitagliptin and α-tocopherol
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a dual arylboronic acid aminothiourea catalytic system for the asymmetric intramolecular hetero michael reaction of α β unsaturated carboxylic acids
ChemInform, 2015Co-Authors: Takumi Azuma, Yusuke Kobayashi, Akihiro Murata, Tsubasa Inokuma, Yoshiji TakemotoAbstract:For the first time aminoboronic acids (such as BNP) are used as efficient catalysts for the direct intramolecular Hetero-Michael Addition to α,β-unsaturated carboxylic acids to give a wide variety of O- and N-containing heterocycles.
Shengping Zheng - One of the best experts on this subject based on the ideXlab platform.
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double hetero michael Addition of n substituted hydroxylamines to quinone monoketals synthesis of bridged isoxazolidines
ChemInform, 2013Co-Authors: Zhiwei Yin, Jinzhu Zhang, Che Liu, Kate Sioson, Matthew Devany, Shengping ZhengAbstract:Quinone monoketals (I) give bridged isoxazolidines in high yields, whereas significantly lower yields are obtained by using substituted substrates (IV).
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double hetero michael Addition of n substituted hydroxylamines to quinone monoketals synthesis of bridged isoxazolidines
Organic Letters, 2013Co-Authors: Zhiwei Yin, Jinzhu Zhang, Che Liu, Kate Sioson, Matthew Devany, Shengping ZhengAbstract:A general synthesis of bridged isoxazolidines from a double Hetero-Michael Addition of N-substituted hydroxylamines to quinone monoketals has been developed. The different Addition order of N-benzylhydroxylamine and N-Boc hydroxylamine is also discussed. Moreover, the various functionalities in the isoxazolidine products allow facile derivatization.
Yunxia Deng - One of the best experts on this subject based on the ideXlab platform.
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regioselective hetero michael Addition of oxygen sulfur and nitrogen nucleophiles to maleimides catalyzed by bf3 oet2
ChemInform, 2015Co-Authors: Yunxia Deng, Wei Zhang, Shengyin ZhaoAbstract:The Addition of oxygen, nitrogen, and sulfur nucleophiles to maleimides catalyzed by boron trifluoride etherate is studied.
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regioselective hetero michael Addition of oxygen sulfur and nitrogen nucleophiles to maleimides catalyzed by bf3 oet2
Synthesis, 2015Co-Authors: Yunxia Deng, Wei Zhang, Shengyin ZhaoAbstract:A practical BF3·OEt2-catalyzed regioselective 1,2-Addition or 1,4-Hetero-Michael Addition of oxygen, sulfur, and nitrogen nucleophiles to maleimides has been developed for the synthesis of alkyl fumarate derivatives or 3-substituted succinimides, respectively. This reaction system has wide substrate scope and gives moderate to excellent yields (up to 96%) of the desired products. In contrast to the base-catalyzed methods, this strategy is very general, simple, environmentally friendly, and tolerant of oxygen.