The Experts below are selected from a list of 38529 Experts worldwide ranked by ideXlab platform
Takahiko Akiyama - One of the best experts on this subject based on the ideXlab platform.
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remarkable differences in reactivity between benzothiazoline and hantzsch ester as a Hydrogen Donor in chiral phosphoric acid catalyzed asymmetric reductive amination of ketones
Chemistry-an Asian Journal, 2016Co-Authors: Kyunghee Kim, Takahiko Akiyama, Cheolhong CheonAbstract:Described herein are differences in behavior between a Hantzsch ester and a benzothiazoline as Hydrogen Donors in the chiral phosphoric acid catalyzed asymmetric reductive amination of ketones with p-anisidine. The asymmetric reductive amination of ketones with a Hantzsch ester as a Hydrogen Donor provided the corresponding chiral amines exclusively, regardless of the structures of the ketones, whereas a similar transformation with a benzothiazoline provided chiral amines and p-methoxyphenyl-protected primary amines in variable yields, depending on the structures of both the ketones and benzothiazolines. Because a benzothiazoline has an N,S-acetal moiety that is vulnerable to p-anisidine, the primary amine can be formed through transimination of the benzothiazoline with p-anisidine followed by reduction of the resulting aldimine with remaining benzothiazoline.
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Benzothiazoline: Versatile Hydrogen Donor for Organocatalytic Transfer Hydrogenation
Accounts of Chemical Research, 2015Co-Authors: Chen Zhu, Kodai Saito, Masahiro Yamanaka, Takahiko AkiyamaAbstract:ConspectusThe asymmetric reduction of ketimines is an important method for the preparation of amines in optically pure form. Inspired by the biological system using NAD(P)H, Hantzsch ester has been extensively employed as a Hydrogen Donor in combination with chiral phosphoric acid for the transfer Hydrogenation of ketimines to furnish amines with high to excellent enantioselectivities.We focused on 2-substituted benzothiazoline as a Hydrogen Donor in the phosphoric acid catalyzed transfer Hydrogenation reaction of ketimines for the following reasons: (1) benzothiazoline is readily prepared just by mixing 2-aminobenzenethiol and aldehyde, (2) both reactivity (Hydrogen donating ability) and enantioselectivity would be controlled by tuning the 2-substituent of benzothiazoline, and (3) benzothiazoline can be stored in a refrigerator under inert atmosphere without conceivable decomposition. Both the 2-position of benzothiazoline and the 3,3′-position of phosphoric acid are tunable in order to achieve excellent...
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Asymmetric transfer Hydrogenation of ketimines by indoline as recyclable Hydrogen Donor.
Organic Letters, 2014Co-Authors: Kodai Saito, Hiromitsu Miyashita, Takahiko AkiyamaAbstract:The chiral phosphoric acid catalyzed enantioselective transfer Hydrogenation of various ketimines was achieved by the use of 2-aryl indoline as the Hydrogen Donor. Corresponding chiral amines were obtained in good chemical yields with excellent enantioselectivities.
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Transfer Hydrogenation of Imines with Carboxyl-Tailed Benzothiazoline as Readily Removable Hydrogen Donor.
ChemInform, 2012Co-Authors: Chen Zhu, Takahiko AkiyamaAbstract:BZT is developed as a novel Hydrogen Donor, which is stable enough to be stored for months in a refrigerator.
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transfer Hydrogenation of imines with carboxyl tailed benzothiazoline as readily removable Hydrogen Donor
Tetrahedron Letters, 2012Co-Authors: Chen Zhu, Takahiko AkiyamaAbstract:A benzothiazoline bearing 4-carboxyphenyl group at 2-position was developed as an efficient Hydrogen Donor for the transfer Hydrogenation reaction. Introduction of the carboxyl group significantly facilitated the removal of the residual benzothiazoline and benzothiazole by washing with aqueous basic solution. The present approach provides a convenient and straightforward access to various amines with broad substrate scope and in good yields.
Zhenyu Liu - One of the best experts on this subject based on the ideXlab platform.
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coke and radicals formation on a sulfided nimo γ al2o3 catalyst during hydroprocessing of an atmospheric residue in Hydrogen Donor media
Fuel Processing Technology, 2017Co-Authors: Lei Shi, Qiaoqiao Zhou, Qingya Liu, Xinge Shi, Ting Wang, Zhenyu LiuAbstract:Abstract Coking on catalyst during hydroprocessing of petroleum residues is an important issue that should be addressed for better catalyst performance. This paper studies reaction and coking behaviors of Maoming atmospheric residue (AR) over a sulfided commercial NiMo/γ-Al 2 O 3 catalyst in the presence and absence of a Hydrogen Donor solvent, tetrahydronaphthalene (THN), in a micro-reactor at temperatures of 400–460 °C and reaction time of 0–60 min. It reports the changes in yields of CS 2 soluble matter (CS 2 -S), CS 2 insoluble matter (coke) and gas, as well as the changes in quantity of coke on the catalyst and in radical concentration of the reaction system, coke on catalyst and CS 2 -S. It is found that compared with the changes in yields, which are significant at temperatures higher than 420 °C, the changes in radical concentration are significant at 400 °C. The catalyst promotes Hydrogen donation of THN, which lowers the amounts of coke formed in the liquid phase, on the catalyst, and the activation energy of coking on the catalyst.
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Coke and radicals formation on a sulfided NiMo/γ-Al2O3 catalyst during hydroprocessing of an atmospheric residue in Hydrogen Donor media
Fuel Processing Technology, 2017Co-Authors: Yuxin Yan, Qiaoqiao Zhou, Qingya Liu, Xinge Shi, Lei Shi, Zhenyu Liu, Ting Wang, Wei HanAbstract:Abstract Coking on catalyst during hydroprocessing of petroleum residues is an important issue that should be addressed for better catalyst performance. This paper studies reaction and coking behaviors of Maoming atmospheric residue (AR) over a sulfided commercial NiMo/γ-Al 2 O 3 catalyst in the presence and absence of a Hydrogen Donor solvent, tetrahydronaphthalene (THN), in a micro-reactor at temperatures of 400–460 °C and reaction time of 0–60 min. It reports the changes in yields of CS 2 soluble matter (CS 2 -S), CS 2 insoluble matter (coke) and gas, as well as the changes in quantity of coke on the catalyst and in radical concentration of the reaction system, coke on catalyst and CS 2 -S. It is found that compared with the changes in yields, which are significant at temperatures higher than 420 °C, the changes in radical concentration are significant at 400 °C. The catalyst promotes Hydrogen donation of THN, which lowers the amounts of coke formed in the liquid phase, on the catalyst, and the activation energy of coking on the catalyst.
Chen Zhu - One of the best experts on this subject based on the ideXlab platform.
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Benzothiazoline: Versatile Hydrogen Donor for Organocatalytic Transfer Hydrogenation
Accounts of Chemical Research, 2015Co-Authors: Chen Zhu, Kodai Saito, Masahiro Yamanaka, Takahiko AkiyamaAbstract:ConspectusThe asymmetric reduction of ketimines is an important method for the preparation of amines in optically pure form. Inspired by the biological system using NAD(P)H, Hantzsch ester has been extensively employed as a Hydrogen Donor in combination with chiral phosphoric acid for the transfer Hydrogenation of ketimines to furnish amines with high to excellent enantioselectivities.We focused on 2-substituted benzothiazoline as a Hydrogen Donor in the phosphoric acid catalyzed transfer Hydrogenation reaction of ketimines for the following reasons: (1) benzothiazoline is readily prepared just by mixing 2-aminobenzenethiol and aldehyde, (2) both reactivity (Hydrogen donating ability) and enantioselectivity would be controlled by tuning the 2-substituent of benzothiazoline, and (3) benzothiazoline can be stored in a refrigerator under inert atmosphere without conceivable decomposition. Both the 2-position of benzothiazoline and the 3,3′-position of phosphoric acid are tunable in order to achieve excellent...
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Transfer Hydrogenation of Imines with Carboxyl-Tailed Benzothiazoline as Readily Removable Hydrogen Donor.
ChemInform, 2012Co-Authors: Chen Zhu, Takahiko AkiyamaAbstract:BZT is developed as a novel Hydrogen Donor, which is stable enough to be stored for months in a refrigerator.
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transfer Hydrogenation of imines with carboxyl tailed benzothiazoline as readily removable Hydrogen Donor
Tetrahedron Letters, 2012Co-Authors: Chen Zhu, Takahiko AkiyamaAbstract:A benzothiazoline bearing 4-carboxyphenyl group at 2-position was developed as an efficient Hydrogen Donor for the transfer Hydrogenation reaction. Introduction of the carboxyl group significantly facilitated the removal of the residual benzothiazoline and benzothiazole by washing with aqueous basic solution. The present approach provides a convenient and straightforward access to various amines with broad substrate scope and in good yields.
Martin Wills - One of the best experts on this subject based on the ideXlab platform.
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rhodium versus ruthenium contrasting behaviour in the asymmetric transfer Hydrogenation of α substituted acetophenones
Tetrahedron-asymmetry, 2001Co-Authors: David J Cross, Jennifer A Kenny, Ian Houson, Lynne Campbell, Tim Walsgrove, Martin WillsAbstract:Abstract The reduction of a number of α-substituted acetophenones has been achieved using both ruthenium(II)- and rhodium(III)-based asymmetric transfer Hydrogenation catalysts employing formic acid as the Hydrogen Donor.
Cheolhong Cheon - One of the best experts on this subject based on the ideXlab platform.
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remarkable differences in reactivity between benzothiazoline and hantzsch ester as a Hydrogen Donor in chiral phosphoric acid catalyzed asymmetric reductive amination of ketones
Chemistry-an Asian Journal, 2016Co-Authors: Kyunghee Kim, Takahiko Akiyama, Cheolhong CheonAbstract:Described herein are differences in behavior between a Hantzsch ester and a benzothiazoline as Hydrogen Donors in the chiral phosphoric acid catalyzed asymmetric reductive amination of ketones with p-anisidine. The asymmetric reductive amination of ketones with a Hantzsch ester as a Hydrogen Donor provided the corresponding chiral amines exclusively, regardless of the structures of the ketones, whereas a similar transformation with a benzothiazoline provided chiral amines and p-methoxyphenyl-protected primary amines in variable yields, depending on the structures of both the ketones and benzothiazolines. Because a benzothiazoline has an N,S-acetal moiety that is vulnerable to p-anisidine, the primary amine can be formed through transimination of the benzothiazoline with p-anisidine followed by reduction of the resulting aldimine with remaining benzothiazoline.
