The Experts below are selected from a list of 288 Experts worldwide ranked by ideXlab platform
Thomas J. Blacklock - One of the best experts on this subject based on the ideXlab platform.
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reductive alkylation of Thioureas a highly practical synthesis of unsymmetrical n n disubstituted Thioureas
Tetrahedron Letters, 2004Co-Authors: Lech Ciszewski, Olijan Repič, Thomas J. BlacklockAbstract:A highly practical synthesis of unsymmetrical N,N′-disubstituted Thioureas by the reductive alkylation of N-monosubstituted Thioureas with aldehydes is described. N-Monosubstituted Thioureas can in turn be synthesized by the reductive amination of Thiourea with an appropriate aldehyde. This reductive alkylation methodology was also extended to carbamates.
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Reductive alkylation of Thioureas: a highly practical synthesis of unsymmetrical N,N′-disubstituted Thioureas
Tetrahedron Letters, 2004Co-Authors: Lech Ciszewski, Olijan Repič, Thomas J. BlacklockAbstract:A highly practical synthesis of unsymmetrical N,N′-disubstituted Thioureas by the reductive alkylation of N-monosubstituted Thioureas with aldehydes is described. N-Monosubstituted Thioureas can in turn be synthesized by the reductive amination of Thiourea with an appropriate aldehyde. This reductive alkylation methodology was also extended to carbamates.
John C G Zhao - One of the best experts on this subject based on the ideXlab platform.
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high enantioselective michael addition of malonates to β γ unsaturated α ketoesters catalyzed by bifunctional Thioureas
Tetrahedron Letters, 2014Co-Authors: Swapna Konda, John C G ZhaoAbstract:Abstract A highly enantioselective Michael addition of malonates to β,γ-unsaturated α-ketoesters was achieved using cinchona alkaloid-derived Thioureas as the bifunctional catalyst. The corresponding Michael addition products were obtained in excellent yields (90–99%) and ee values (up to >99% ee) using a quinidine-derived Thiourea as the catalyst under neat conditions. The opposite enantiomer may be obtained using a quinine- or cinchonidine-derived Thiourea as the catalyst.
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Michael Addition of Ketones and Aldehydes to Maleimides Catalyzed by Modularly Designed Organocatalysts
Advanced Synthesis & Catalysis, 2013Co-Authors: Savitha Muramulla, Jun-an Ma, John C G ZhaoAbstract:Modularly designed organocatalysts (MDOs) formed in situ from the self-assembly of primary α-amino acids and Cinchona alkaloid Thioureas were found to be excellent catalysts for the stereoselective Michael addition of enolizable ketones and aldehydes to maleimides. Using an MDO formed from quinidine Thiourea and L-2-chlorophenylglycine, the corresponding Michael addition products, 3-substituted succinimides, may be obtained in excellent yields and high enantio- and diastereoselectivities.
Yoshiji Takemoto - One of the best experts on this subject based on the ideXlab platform.
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Synthesis and properties of chiral Thioureas bearing an additional function at a remote position tethered by a 1,5-disubstituted triazole.
Molecules (Basel Switzerland), 2010Co-Authors: Kiyosei Takasu, Takumi Azuma, Iderbat Enkhtaivan, Yoshiji TakemotoAbstract:The synthesis and properties of multifunctional Thioureas bearing a variety of functional groups at a position remote from the Thiourea moiety are described. A 1,5-disubstituted triazole tether connected with a Thiourea and another functional group was synthesized via ruthenium catalyzed Huisgen cycloaddition. We demonstrate the utility of the synthetic Thioureas as asymmetric catalysts and probes for the mechanistic elucidation of the course of the Michael reaction of an α,ß-unsaturated imide.
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development of chiral Thiourea catalysts and its application to asymmetric catalytic reactions
Chemical & Pharmaceutical Bulletin, 2010Co-Authors: Yoshiji TakemotoAbstract:We have developed several multifunctional Thiourea catalysts bearing a tertiary amine or an 1,2-amino alcohol in expectation of their synchronous activation of a nucleophile and an electrophile through both acid-base and hydrogen-bonding interactions. From these studies, it was revealed that the weak acidity of Thioureas compared with metallic Lewis acids could be overcome by this modification. The bifunctional aminoThiourea could be used efficiently for a wide range of diastereoselective and enantioselective nucleophilic reactions such as Michael addition of 1,3-dicarbonyl compounds to nitroolefines, aza-Henry reaction of nitroalkanes to N-Boc imines, and hydrazination of cyclic β-keto esters. We also discovered that multifunctional Thiourea catalyst, bearing an 1,2-amino alcohol moiety, significantly accelerated the Petasis-type reaction of alkenylboronic acids to N-phenoxycarbonyl quinolinium salts, prepared from quinolines and phenyl chloroformate, to afford 1,2-addition products with high enantioselectivity (up to 97% ee). Furthermore, to expand the synthetic applicability of the Thiourea-catalyzed asymmetric reactions, tandem organocatalyzed reactions were explored to establish the concise one-pot synthesis of chiral densely functionalized three-, five-, and six-membered compounds.
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Synthesis of trifunctional Thioureas bearing 1,5-disubstituted triazole tether by Ru-catalyzed Huisgen cycloaddition
Tetrahedron Letters, 2010Co-Authors: Kiyosei Takasu, Takumi Azuma, Yoshiji TakemotoAbstract:Abstract Synthesis of trifunctional Thiourea catalysts tethered with a variety of functional group is described. 1,5-Triazole tether in the catalysts was constructed by ruthenium-catalyzed Huisgen cycloaddition. We demonstrate the utility of the synthetic Thioureas as an asymmetric catalyst for Michal addition of nitrostyrene with cyclohexanone.
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The amino Thiourea-catalyzed asymmetric nucleophilic reactions
CHIMIA International Journal for Chemistry, 2007Co-Authors: Yoshiji Takemoto, Hideto MiyabeAbstract:Bifunctional amino Thiourea-catalyzed asymmetric additions of several nucleophiles into electron-deficient unsaturated compounds such as nitroolefins, α,β-unsaturated imides, imines, and azodicarboxylates are described. We discovered that bifunctional Thioureas bearing a tertiary amino group significantly accelerated several nucleophilic addition reactions of active methylene compounds to electron-deficient double bonds. In these reactions, a strong hydrogen-bonding ability of the Thiourea moiety as well as an appropriate Bronsted basicity of the tertiary amine is crucial for high enantioselectivity. This dual activation of both nucleophiles and electrophiles by the bifunctional Thiourea expanded the applicability of the Thiourea-catalyzed enantioselective reaction. In addition, these organocatalyzed asymmetric reactions were successfully applied to the concise asymmetric synthesis of natural products and medicinal candidates such as epibatidine, baclofen, and CP-99,994.
Lech Ciszewski - One of the best experts on this subject based on the ideXlab platform.
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reductive alkylation of Thioureas a highly practical synthesis of unsymmetrical n n disubstituted Thioureas
Tetrahedron Letters, 2004Co-Authors: Lech Ciszewski, Olijan Repič, Thomas J. BlacklockAbstract:A highly practical synthesis of unsymmetrical N,N′-disubstituted Thioureas by the reductive alkylation of N-monosubstituted Thioureas with aldehydes is described. N-Monosubstituted Thioureas can in turn be synthesized by the reductive amination of Thiourea with an appropriate aldehyde. This reductive alkylation methodology was also extended to carbamates.
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Reductive alkylation of Thioureas: a highly practical synthesis of unsymmetrical N,N′-disubstituted Thioureas
Tetrahedron Letters, 2004Co-Authors: Lech Ciszewski, Olijan Repič, Thomas J. BlacklockAbstract:A highly practical synthesis of unsymmetrical N,N′-disubstituted Thioureas by the reductive alkylation of N-monosubstituted Thioureas with aldehydes is described. N-Monosubstituted Thioureas can in turn be synthesized by the reductive amination of Thiourea with an appropriate aldehyde. This reductive alkylation methodology was also extended to carbamates.
Isabel Rozas - One of the best experts on this subject based on the ideXlab platform.
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copper ii chloride promoted transformation of amines into guanidines and asymmetrical n n disubstituted guanidines
Tetrahedron Letters, 2013Co-Authors: Brendan Kelly, Isabel RozasAbstract:Abstract We present a concise, less-toxic and broadly applicable method for coupling weakly nucleophilic amines with N,N′-di-(tert-butoxycarbonyl)Thiourea, N-(tert-butxoycarbonyl), N′-alkyl/arylsubstituted-Thioureas and N,N′-di-(tert-butoxycarbonyl)imidazolidine-2-thione in the presence of copper(II) chloride. Subsequent removal of Boc protecting groups affords guanidines, di-substituted guanidines and 2-aminoimidazolines in modest to excellent overall yields.
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a concise synthesis of asymmetrical n n disubstituted guanidines
Tetrahedron Letters, 2011Co-Authors: Daniel H Odonovan, Isabel RozasAbstract:Abstract We present a new and concise method for the preparation of asymmetrical N,N′-disubstituted guanidines starting from Thiourea via the reaction of N-Boc-protected N′-alkyl/aryl substituted Thioureas with an amine in the presence of mercury(II) chloride and triethylamine.
