The Experts below are selected from a list of 315 Experts worldwide ranked by ideXlab platform
Jose M Sansano - One of the best experts on this subject based on the ideXlab platform.
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silver catalysed multicomponent 1 3 dipolar cycloaddition of 2 oxoaldehydes derived azomethine ylides
Tetrahedron, 2015Co-Authors: Juan Manceboaracil, Carmen Najera, Alberto Cayuelas, Jose M SansanoAbstract:Abstract The silver-catalysed multicomponent reaction between Ethyl Glyoxylate, 2,2-dimethoxyacetaldehyde, or phenylglyoxal as aldehyde components with a α-amino ester hydrochloride and a dipolarophile in the presence of triEthylamine is described. This domino process takes place at room temperature by in situ liberation of the α-amino ester followed by the formation of the imino ester, which is the precursor of a metalloazomethine ylide. The cycloaddition of this species and the corresponding dipolarophile affords polysubstituted proline derivatives. Ethyl Glyoxylate reacts with glycinate, alaninate, phenylalaninate and phenylglycinate at room temperature in the presence of representative dipolarophiles affording endo-2,5-cis-cycloadducts in good yields and high diastereoselection. In addition, 2,2-dimethoxyacetaldehyde is evaluated with the same amino esters and dipolarophiles, under the same mild conditions, generating the corresponding endo-2,5-cis-cycloadducts with higher diastereoselections than the obtained in the same reactions using Ethyl Glyoxylate. In the case of phenylglyoxal the corresponding 5-benzoyl-endo-2,5-cis cycloadducts are obtained in short reaction times and similar diasteroselection.
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binap silver catalyzed enantioselective multicomponent 1 3 dipolar cycloaddition of azomethines ylides derived from Ethyl Glyoxylate
Tetrahedron-asymmetry, 2015Co-Authors: Juan Manceboaracil, Carmen Najera, Jose M SansanoAbstract:Abstract The enantioselective binap–silver catalyzed multicomponent 1,3-dipolar cycloaddition using Ethyl Glyoxylate, phenylalanine Ethyl ester, and maleimides is described. The employment of basic silver carbonate allows the reaction to take place in the absence of an extra base giving high yields and ee. In addition, low-level calculations regarding the importance of the benzyl substituent at the α-position of the amino ester justify the expected absolute configuration of the final cycloadducts and the observed high enantiodiscrimination.
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microwave assisted multicomponent diastereoselective 1 3 dipolar cycloaddition of Ethyl Glyoxylate derived azomethine ylides
Organic and Biomolecular Chemistry, 2013Co-Authors: Juan Manceboaracil, Carmen Najera, Jose M SansanoAbstract:The thermal multicomponent 1,3-dipolar cycloaddition (1,3-DC) of diEthyl aminomalonate or α-amino esters (derived from glycine, alanine, phenylalanine, and phenylglycine) with Ethyl Glyoxylate and the corresponding dipolarophile such as maleimides, mEthyl acrylate, mEthyl fumarate, (E)-1,2-bis(phenylsulfonyl)Ethylene, and electron deficient alkynes allows the diastereoselective synthesis of new polysubstituted pyrrolidine derivatives. Microwave-assisted heating processes give better results than conventional heating ones, affording endo-cycloadducts as major stereoisomers. In general, 2,5-cis-cycloadducts are preferentially formed according to the previous formation of the W-shaped dipole. Only in the 1,3-DC of the disulfone with phenylglycine and Ethyl Glyoxylate the corresponding exo-trans-cycloadduct was isolated. The compound endo-cis-4b, derived from phenylalanine, Ethyl Glyoxylate and N-benzylmaleimide, has been further transformed into a very complex diazabicyclo[2.2.1]octane skeleton with potential biological activity.
Kuiling Ding - One of the best experts on this subject based on the ideXlab platform.
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self supported heterogeneous titanium catalysts for enantioselective carbonyl ene and sulfoxidation reactions
Chemistry: A European Journal, 2005Co-Authors: Xisheng Wang, Xingwang Wang, Hongchao Guo, Zheng Wang, Kuiling DingAbstract:A new strategy for the heterogenization of chiral titanium complexes was developed by the in situ assembly of bridged multitopic BINOL ligands with [Ti(OiPr)4] without using a support. The assembled heterogeneous catalysts (self-supported) showed excellent enantioselectivity in both the carbonyl-ene reaction of alpha-mEthylstyrene with Ethyl Glyoxylate (up to 98 % ee) and the oxidation of sulfides (up to >99 % ee). The catalytic performance of these heterogeneous catalytic systems was comparable or even superior to that attained with their homogeneous counterparts. The spacers between the two BINOL units of the ligands in the assembled catalysts had significant impact on the enantioselectivity of the carbonyl-ene reaction. This demonstrates the importance of the supramolecular structures of the assemblies on their catalytic behavior. In the catalysis of sulfoxidation, the self-supported heterogeneous titanium catalysts were highly stable and could be readily recycled and reused for over one month (at least eight cycles) without significant loss of activity and enantioselectivity (up to >99.9 % ee). The features of these self-supported catalysts, such as facile preparation, robust chiral structure of solid-state catalysts, high density of the catalytically active units in the solids, as well as easy recovery and simple recycling, are particularly important in developing methods for the synthesis of optically active compounds in industrial processes.
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highly enantioselective friedel crafts reaction of aromatic amines with Ethyl Glyoxylate catalyzed by chiral titanium iv complexes practical synthesis of aminomandelic acid derivatives
Journal of Organic Chemistry, 2004Co-Authors: Yu Yuan, Xingwang Wang, Xin Li, Kuiling DingAbstract:The asymmetric Friedel−Crafts reaction of a variety of N,N-dialkylanilines with Ethyl Glyoxylate has been achieved by the catalysis of titanium complexes of BINOL derivatives to give corresponding Ethyl esters of p-N,N-dialkylaminomandelic acids in high yields (85−99%) and good to excellent enantioselectivities (80−96.6% ee) under the optimized reaction conditions, which has added a new catalyst for this class of reactions. The reaction could also be carried out at a reduced catalyst loading (1 mol %) in gram scale, which provided a practical synthesis of enantiopure aminomandelic acid derivatives.
Juan Manceboaracil - One of the best experts on this subject based on the ideXlab platform.
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silver catalysed multicomponent 1 3 dipolar cycloaddition of 2 oxoaldehydes derived azomethine ylides
Tetrahedron, 2015Co-Authors: Juan Manceboaracil, Carmen Najera, Alberto Cayuelas, Jose M SansanoAbstract:Abstract The silver-catalysed multicomponent reaction between Ethyl Glyoxylate, 2,2-dimethoxyacetaldehyde, or phenylglyoxal as aldehyde components with a α-amino ester hydrochloride and a dipolarophile in the presence of triEthylamine is described. This domino process takes place at room temperature by in situ liberation of the α-amino ester followed by the formation of the imino ester, which is the precursor of a metalloazomethine ylide. The cycloaddition of this species and the corresponding dipolarophile affords polysubstituted proline derivatives. Ethyl Glyoxylate reacts with glycinate, alaninate, phenylalaninate and phenylglycinate at room temperature in the presence of representative dipolarophiles affording endo-2,5-cis-cycloadducts in good yields and high diastereoselection. In addition, 2,2-dimethoxyacetaldehyde is evaluated with the same amino esters and dipolarophiles, under the same mild conditions, generating the corresponding endo-2,5-cis-cycloadducts with higher diastereoselections than the obtained in the same reactions using Ethyl Glyoxylate. In the case of phenylglyoxal the corresponding 5-benzoyl-endo-2,5-cis cycloadducts are obtained in short reaction times and similar diasteroselection.
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binap silver catalyzed enantioselective multicomponent 1 3 dipolar cycloaddition of azomethines ylides derived from Ethyl Glyoxylate
Tetrahedron-asymmetry, 2015Co-Authors: Juan Manceboaracil, Carmen Najera, Jose M SansanoAbstract:Abstract The enantioselective binap–silver catalyzed multicomponent 1,3-dipolar cycloaddition using Ethyl Glyoxylate, phenylalanine Ethyl ester, and maleimides is described. The employment of basic silver carbonate allows the reaction to take place in the absence of an extra base giving high yields and ee. In addition, low-level calculations regarding the importance of the benzyl substituent at the α-position of the amino ester justify the expected absolute configuration of the final cycloadducts and the observed high enantiodiscrimination.
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microwave assisted multicomponent diastereoselective 1 3 dipolar cycloaddition of Ethyl Glyoxylate derived azomethine ylides
Organic and Biomolecular Chemistry, 2013Co-Authors: Juan Manceboaracil, Carmen Najera, Jose M SansanoAbstract:The thermal multicomponent 1,3-dipolar cycloaddition (1,3-DC) of diEthyl aminomalonate or α-amino esters (derived from glycine, alanine, phenylalanine, and phenylglycine) with Ethyl Glyoxylate and the corresponding dipolarophile such as maleimides, mEthyl acrylate, mEthyl fumarate, (E)-1,2-bis(phenylsulfonyl)Ethylene, and electron deficient alkynes allows the diastereoselective synthesis of new polysubstituted pyrrolidine derivatives. Microwave-assisted heating processes give better results than conventional heating ones, affording endo-cycloadducts as major stereoisomers. In general, 2,5-cis-cycloadducts are preferentially formed according to the previous formation of the W-shaped dipole. Only in the 1,3-DC of the disulfone with phenylglycine and Ethyl Glyoxylate the corresponding exo-trans-cycloadduct was isolated. The compound endo-cis-4b, derived from phenylalanine, Ethyl Glyoxylate and N-benzylmaleimide, has been further transformed into a very complex diazabicyclo[2.2.1]octane skeleton with potential biological activity.
Carmen Najera - One of the best experts on this subject based on the ideXlab platform.
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silver catalysed multicomponent 1 3 dipolar cycloaddition of 2 oxoaldehydes derived azomethine ylides
Tetrahedron, 2015Co-Authors: Juan Manceboaracil, Carmen Najera, Alberto Cayuelas, Jose M SansanoAbstract:Abstract The silver-catalysed multicomponent reaction between Ethyl Glyoxylate, 2,2-dimethoxyacetaldehyde, or phenylglyoxal as aldehyde components with a α-amino ester hydrochloride and a dipolarophile in the presence of triEthylamine is described. This domino process takes place at room temperature by in situ liberation of the α-amino ester followed by the formation of the imino ester, which is the precursor of a metalloazomethine ylide. The cycloaddition of this species and the corresponding dipolarophile affords polysubstituted proline derivatives. Ethyl Glyoxylate reacts with glycinate, alaninate, phenylalaninate and phenylglycinate at room temperature in the presence of representative dipolarophiles affording endo-2,5-cis-cycloadducts in good yields and high diastereoselection. In addition, 2,2-dimethoxyacetaldehyde is evaluated with the same amino esters and dipolarophiles, under the same mild conditions, generating the corresponding endo-2,5-cis-cycloadducts with higher diastereoselections than the obtained in the same reactions using Ethyl Glyoxylate. In the case of phenylglyoxal the corresponding 5-benzoyl-endo-2,5-cis cycloadducts are obtained in short reaction times and similar diasteroselection.
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binap silver catalyzed enantioselective multicomponent 1 3 dipolar cycloaddition of azomethines ylides derived from Ethyl Glyoxylate
Tetrahedron-asymmetry, 2015Co-Authors: Juan Manceboaracil, Carmen Najera, Jose M SansanoAbstract:Abstract The enantioselective binap–silver catalyzed multicomponent 1,3-dipolar cycloaddition using Ethyl Glyoxylate, phenylalanine Ethyl ester, and maleimides is described. The employment of basic silver carbonate allows the reaction to take place in the absence of an extra base giving high yields and ee. In addition, low-level calculations regarding the importance of the benzyl substituent at the α-position of the amino ester justify the expected absolute configuration of the final cycloadducts and the observed high enantiodiscrimination.
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glyoxylic acid versus Ethyl Glyoxylate for the aqueous enantio selective synthesis of α hydroxy γ keto acids and esters by the n tosyl s a binam l prolinamide organocatalyzed aldol reaction
Synthesis, 2014Co-Authors: Fernando J N Moles, Carmen Najera, Gabriela Guillena, Enrique GomezbengoaAbstract:N-Tosyl-(S a)-binam- l -prolinamide is an efficient catalyst for the aqueous aldol reaction between ketones and glyoxylic acid, as the monohydrate or as an aqueous solution, or a 50% toluene solution of Ethyl Glyoxylate. These reactions led to the formation of chiral α-hydroxy-γ-keto carboxylic acids and esters in high levels of diastereo- and enantioselectivities (up to 97% ee), providing mainly anti aldol products. Only cyclopentanone and cyclohexane-1,4-dione afforded an almost 1:1 mixture of the syn/anti-diastereoisomers; however, the reaction between 4-phenylcyclohexanone and Ethyl Glyoxylate gave the corresponding syn,syn-product as the major diastereoisomer.
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microwave assisted multicomponent diastereoselective 1 3 dipolar cycloaddition of Ethyl Glyoxylate derived azomethine ylides
Organic and Biomolecular Chemistry, 2013Co-Authors: Juan Manceboaracil, Carmen Najera, Jose M SansanoAbstract:The thermal multicomponent 1,3-dipolar cycloaddition (1,3-DC) of diEthyl aminomalonate or α-amino esters (derived from glycine, alanine, phenylalanine, and phenylglycine) with Ethyl Glyoxylate and the corresponding dipolarophile such as maleimides, mEthyl acrylate, mEthyl fumarate, (E)-1,2-bis(phenylsulfonyl)Ethylene, and electron deficient alkynes allows the diastereoselective synthesis of new polysubstituted pyrrolidine derivatives. Microwave-assisted heating processes give better results than conventional heating ones, affording endo-cycloadducts as major stereoisomers. In general, 2,5-cis-cycloadducts are preferentially formed according to the previous formation of the W-shaped dipole. Only in the 1,3-DC of the disulfone with phenylglycine and Ethyl Glyoxylate the corresponding exo-trans-cycloadduct was isolated. The compound endo-cis-4b, derived from phenylalanine, Ethyl Glyoxylate and N-benzylmaleimide, has been further transformed into a very complex diazabicyclo[2.2.1]octane skeleton with potential biological activity.
Viresh H. Rawal - One of the best experts on this subject based on the ideXlab platform.
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highly enantioselective carbonyl ene reactions catalyzed by a hindered silyl salen cobalt complex
Organic Letters, 2007Co-Authors: Gerri E Hutson, Apurva Dave, Viresh H. RawalAbstract:We report here the enantioselective carbonyl-ene reactions of various 1,1-disubstituted and trisubstituted alkenes with Ethyl Glyoxylate. The reactions are catalyzed by a new Co−salen complex, in which bulky triisobutylsilyl (TIBS) substituents occupy the positions ortho to the phenolic oxygens. This complex catalyzes the reactions under nearly ideal conditionsat room temperature and using catalyst loadings as low as 0.1 mol %and provides the chiral, homoallylic alcohol products in excellent yields, enantioselectivities, and diastereoselectivities.