The Experts below are selected from a list of 14865 Experts worldwide ranked by ideXlab platform
Hongjun Zhu - One of the best experts on this subject based on the ideXlab platform.
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generation of oxazolidine 2 4 diones bearing sulfur substituted Quaternary Carbon atoms by oxothiolation cyclization of ynamides
ChemInform, 2016Co-Authors: Hai Huang, Junzhen Fan, Zhimin Yang, Xiaodong Jin, Qi Liu, Hongjun ZhuAbstract:A novel method for the metal-free oxothiolation of ynamides to construct oxazolidine-2,4-diones bearing sulfur-substituted Quaternary Carbon atoms is developed.
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generation of oxazolidine 2 4 diones bearing sulfur substituted Quaternary Carbon atoms by oxothiolation cyclization of ynamides
Chemistry: A European Journal, 2016Co-Authors: Hai Huang, Junzhen Fan, Zhimin Yang, Xiaodong Jin, Qi Liu, Hongjun ZhuAbstract:A novel method for metal-free oxothiolation of ynamides to construct oxazolidine-2,4-diones bearing sulfur-substituted Quaternary Carbon atoms has been developed. It represents a rare C-O bond cleavage of ynamides, as well as a facile and tandem approach for the formation of C-O, C-S, and C-Cl bonds. This redox-neutral protocol can be applied to the synthesis of multisubstituted oxazolidine-2,4-diones with good chemoselectivity and good yields of isolated products under mild conditions.
Michael J Krische - One of the best experts on this subject based on the ideXlab platform.
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cyclometalated iridium phanephos complexes are active catalysts in enantioselective allene fluoral reductive coupling and related alcohol mediated Carbonyl additions that form acyclic Quaternary Carbon stereocenters
Journal of the American Chemical Society, 2019Co-Authors: Leyah A Schwartz, Kuowei Huang, Michael C Holmes, Gilmar A Brito, Theo P Goncalves, J Richardson, Craig J Ruble, Michael J KrischeAbstract:Iridium complexes modified by the chiral phosphine ligand PhanePhos catalyze the 2-propanol-mediated reductive coupling of diverse 1,1-disubstituted allenes 1a–1u with fluoral hydrate 2a to form CF3-substituted secondary alcohols 3a–3u that incorporate acyclic Quaternary Carbon-containing stereodiads. By exploiting concentration-dependent stereoselectivity effects related to the interconversion of kinetic (Z)- and thermodynamic (E)-σ-allyliridium isomers, adducts 3a–3u are formed with complete levels of branched regioselectivity and high levels of anti-diastereo- and enantioselectivity. The utility of this method for construction of CF3-oxetanes and CF3-azetidines is illustrated by the formation of 4a and 6a, respectively. Studies of the reaction mechanism aimed at illuminating the singular effectiveness of PhanePhos as a supporting ligand in this and related transformations have led to the identification of a chromatographically stable cyclometalated iridium–(R)-PhanePhos complex, Ir-PP-I, that is cataly...
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Cyclometalated Iridium–PhanePhos Complexes Are Active Catalysts in Enantioselective Allene–Fluoral Reductive Coupling and Related Alcohol-Mediated Carbonyl Additions That Form Acyclic Quaternary Carbon Stereocenters
2019Co-Authors: Leyah A. Schwartz, Kuowei Huang, Michael Holmes, Gilmar A Brito, J Richardson, Craig J Ruble, Théo P. Gonçalves, Michael J KrischeAbstract:Iridium complexes modified by the chiral phosphine ligand PhanePhos catalyze the 2-propanol-mediated reductive coupling of diverse 1,1-disubstituted allenes 1a–1u with fluoral hydrate 2a to form CF3-substituted secondary alcohols 3a–3u that incorporate acyclic Quaternary Carbon-containing stereodiads. By exploiting concentration-dependent stereoselectivity effects related to the interconversion of kinetic (Z)- and thermodynamic (E)-σ-allyliridium isomers, adducts 3a–3u are formed with complete levels of branched regioselectivity and high levels of anti-diastereo- and enantioselectivity. The utility of this method for construction of CF3-oxetanes and CF3-azetidines is illustrated by the formation of 4a and 6a, respectively. Studies of the reaction mechanism aimed at illuminating the singular effectiveness of PhanePhos as a supporting ligand in this and related transformations have led to the identification of a chromatographically stable cyclometalated iridium–(R)-PhanePhos complex, Ir-PP-I, that is catalytically competent for allene–fluoral reductive coupling and previously reported transfer hydrogenative C–C couplings of dienes or CF3-allenes with methanol. Deuterium labeling studies, reaction progress kinetic analysis (RPKA) and computational studies corroborate a catalytic mechanism involving rapid allene hydrometalation followed by turnover-limiting Carbonyl addition. A computationally determined stereochemical model shows that the ortho-CH2 group of the cyclometalated iridium–PhanePhos complex plays a key role in directing diastereo- and enantioselectivity. The collective data provide key insights into the structural–interactional features of allyliridium complexes required to enforce nucleophilic character, which should inform the design of related cyclometalated catalysts for umpoled allylation
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acyclic Quaternary Carbon stereocenters via enantioselective transition metal catalysis
Chemical Reviews, 2017Co-Authors: Jiajie Feng, Michael Holmes, Michael J KrischeAbstract:Whereas numerous asymmetric methods for formation of Quaternary Carbon stereocenters in cyclic systems have been documented, the construction of acyclic Quaternary Carbon stereocenters with control of absolute stereochemistry remains a formidable challenge. This Review summarizes enantioselective methods for the construction of acyclic Quaternary Carbon stereocenters from achiral or chiral racemic reactants via transition metal catalysis.
Ilan Marek - One of the best experts on this subject based on the ideXlab platform.
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diastereodivergent combined carbometalation zinc homologation c c fragmentation reaction as an efficient tool to prepare acyclic allylic Quaternary Carbon stereocenters
Chemical Science, 2016Co-Authors: Sudipta Raha Roy, Dorian Didier, Amir Kleiner, Ilan MarekAbstract:A new strategy has been developed to construct enantiomerically enriched acyclic allylic Quaternary Carbon stereocenters in a single-pot operation through a combined carbometalation/zinc homologation/fragmentation sequence. Proper tuning of the reaction conditions enables the synthesis of the two enantiomers starting from a single enantiomer of the starting material.
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stereodefined acyclic polysubstituted silyl ketene aminals asymmetric formation of aldol products with Quaternary Carbon stereocenters
ChemInform, 2016Co-Authors: Zackaria Nairoukh, Ilan MarekAbstract:Stereodefined polysubstituted silyl ketene aminals are easily regioselectively and stereoselectively obtained and utilized in Mukaiyama aldol reactions with various aliphatic aldehydes involving the formation of Quaternary Carbon centers in α-position to the Carbonyl groups.
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stereodefined acyclic polysubstituted silyl ketene aminals asymmetric formation of aldol products with Quaternary Carbon stereocenters
Angewandte Chemie, 2015Co-Authors: Zackaria Nairoukh, Ilan MarekAbstract:The regio- and stereoselective formation of stereodefined polysubstituted silyl ketene aminals is easily achieved through selective combined carbometalation-oxidation-silylation reactions. These substrates are ideal candidates for Mukaiyama aldol reactions with aliphatic aldehydes as they give the aldol products with a Quaternary Carbon stereocenter α to the Carbonyl groups in outstanding diastereoselectivities.
Min Shi - One of the best experts on this subject based on the ideXlab platform.
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copper catalyzed trifluoromethylazidation and rearrangement of aniline linked 1 7 enynes access to cf3 substituted azaspirocyclic dihydroquinolin 2 ones and furoindolines
Chemical Communications, 2017Co-Authors: Yin Wei, Min ShiAbstract:A set of reactions involving copper-catalyzed trifluoromethylazidation and then rearrangement of aniline-linked 1,7-enynes with the relatively poorly reactive Togni reagent I and TMSN3 was developed, and provided facile access to structurally diverse and useful CF3-substituted azaspirocyclic dihydroquinolin-2-ones bearing two adjacent Quaternary Carbon centers. We were also able to obtain these products on a large scale. Moreover, the obtained products were further transformed into a range of synthetically valuable furoindolines bearing three consecutive Quaternary Carbon centers after reduction by NaBH4. Also, the delivery of multi-functionalized aziridines as a result of alcoholysis and LiAlH4-reduction of corresponding dihydroquinolin-2-ones 2ba demonstrated the synthetic value of this newly developed protocol.
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diastereo and enantioselective michael addition of 3 substituted oxindoles to trifluoromethyl substituted nitro olefins catalyzed by a cinchona alkaloid derived squaramide
ChemInform, 2014Co-Authors: Meixin Zhao, Min Shi, Xiaoli Zhao, Zezheng HanAbstract:The title reaction of 3-aryloxindoles is efficient and allows highly diastereo- and enantioselective access to 3,3-disubstituted oxindoles bearing a trifluoromethyl substituted tertiary stereocenter adjacent to a Quaternary Carbon atom.
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enantioselective michael addition of 3 aryloxindoles to a vinyl bisphosphonate ester catalyzed by a cinchona alkaloid derived thiourea catalyst
ChemInform, 2013Co-Authors: Meixin Zhao, Min Shi, Tonglei Dai, Ran Liu, Dengke Wei, Hao ZhouAbstract:The Michael adducts (III), containing a chiral Quaternary Carbon center and geminal bisphosphonate ester fragment at the 3-position of the oxindole, are obtained in moderate to good enantioselectivities.
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synthesis of Quaternary Carbon centered chromans from the reactions of ethyl 2 2 hydroxyaryl 2 oxoacetates with allenic ester or allenic sulfone catalyzed by tertiary phosphine and spts
Tetrahedron, 2012Co-Authors: Xiaoyang Guan, Min ShiAbstract:Cyclization reactions of ethyl 2-(2-hydroxyaryl)-2-oxoacetates with ethyl 2,3-butadienoate and allenylsulfone proceeded smoothly in the presence of tertiary phosphine and sodium p-toluenesulfinate (SPTS) to give the corresponding Quaternary Carbon centered chromans in moderate to good yields under mild conditions, which provides an alternative efficient approach for the synthesis of biologically active chroman products.
Hai Huang - One of the best experts on this subject based on the ideXlab platform.
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generation of oxazolidine 2 4 diones bearing sulfur substituted Quaternary Carbon atoms by oxothiolation cyclization of ynamides
ChemInform, 2016Co-Authors: Hai Huang, Junzhen Fan, Zhimin Yang, Xiaodong Jin, Qi Liu, Hongjun ZhuAbstract:A novel method for the metal-free oxothiolation of ynamides to construct oxazolidine-2,4-diones bearing sulfur-substituted Quaternary Carbon atoms is developed.
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generation of oxazolidine 2 4 diones bearing sulfur substituted Quaternary Carbon atoms by oxothiolation cyclization of ynamides
Chemistry: A European Journal, 2016Co-Authors: Hai Huang, Junzhen Fan, Zhimin Yang, Xiaodong Jin, Qi Liu, Hongjun ZhuAbstract:A novel method for metal-free oxothiolation of ynamides to construct oxazolidine-2,4-diones bearing sulfur-substituted Quaternary Carbon atoms has been developed. It represents a rare C-O bond cleavage of ynamides, as well as a facile and tandem approach for the formation of C-O, C-S, and C-Cl bonds. This redox-neutral protocol can be applied to the synthesis of multisubstituted oxazolidine-2,4-diones with good chemoselectivity and good yields of isolated products under mild conditions.
