- Development of Chiral Organosuperbase Catalysts Consisting of Two Different Organobase Functionalities
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In the field of chiral Br?nsted base catalysis, a new generation of chiral catalysts has been highly anticipated to overcome the intrinsic limitation of pronucleophiles that are applicable to the enantioselective reactions. Herein, we reveal conceptually new chiral Br?nsted base catalysts consisting of two different organobase functionalities, one of which functions as an organosuperbase and the other as the substrate recognition site. Their prominent activity, which stems from the distinctive cooperative function by the two organobases in a single catalyst molecule, was demonstrated in the unprecedented enantioselective direct Mannich-type reaction of α-phenylthioacetate as a less acidic pronucleophile. The present achievement would provide a new guiding principle for the design and development of chiral Br?nsted base catalysts and significantly broaden the utility of Br?nsted base catalysis in asymmetric organic synthesis.
- Kondoh, Azusa,Oishi, Masafumi,Terada, Masahiro,Tezuka, Hikaru
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p. 7472 - 7477
(2020/03/19)
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- First example of an organocatalytic asymmetric Mannich reaction between aldimines of glycinates and sulphonyl imines
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The catalytic enantioselective Mannich-type reaction between glycinate Schiff base and imines has been one of the most efficient routes for accessing α,β-diamino acids. However, the glycinate Schiff bases used in the references were almost ketimines. Only
- Wu, Lei,Li, Guangxun,He, Migu,Wang, Yingwei,Zhao, Gang,Tang, Zhuo
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supporting information
p. 769 - 772
(2016/10/24)
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- Catalytic performance of polystyrene-bound ChibaG derivatives as guanidine organobases in asymmetric Michael additions
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The guanidine organocatalyst, ChibaG, was bound via an ether linkage to the phenyl group of the 2-imino substituent to Merrifield resin. Polystyrene-bound ChibaG acted as an effective catalyst in the Michael reaction of tert-butyl N-(diphenylmethylidene)g
- Ishikawa, Tsutomu,Heima, Takashi,Yoshida, Makoto,Kumamoto, Takuya
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p. 307 - 314
(2014/04/03)
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- NOVEL PHASE TRANSFER CATALYSTS
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Compounds of formula (I): wherein R1 to R8, and X- are defined herein. Also disclosed are methods of making and using these compounds.
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Page/Page column 9-10
(2012/05/19)
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- Pentanidium-catalyzed enantioselective α-hydroxylation of oxindoles using molecular oxygen
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Pentanidium-catalyzed α-hydroxylation of 3-substituted-2-oxindoles using molecular oxygen has been developed with good yields and enantioselectivities. This reaction does not require an additional reductant such as triethyl phosphite, which was typically added to reduce the peroxide intermediate. The reaction was demonstrated to consist of two-steps: an enantioselective formation of hydroperoxide oxindole and a kinetic resolution of the hydroperoxide oxindole via reduction with enolates generated from the oxindoles.
- Yang, Yuanyong,Moinodeen, Farhana,Chin, Willy,Ma, Ting,Jiang, Zhiyong,Tan, Choon-Hong
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supporting information
p. 4762 - 4765
(2013/01/15)
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- Pentanidium-catalyzed enantioselective phase-transfer conjugate addition reactions
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A new chiral entity, pentanidium, has been shown to be an excellent chiral phase-transfer catalyst. The enantioselective Michael addition reactions of tert-butyl glycinate-benzophenone Schiff base with various α,β- unsaturated acceptors provide adducts with high enantioselectivities. A successful gram-scale experiment at a low catalyst loading of 0.05 mol % indicates the potential for practical applications of this methodology. Phosphoglycine ester analogues can also be utilized as the Michael donor, affording enantioenriched α-aminophosphonic acid derivatives and phosphonic analogues of (S)-proline.
- Ma, Ting,Fu, Xiao,Kee, Choon Wee,Zong, Lili,Pan, Yuanhang,Huang, Kuo-Wei,Tan, Choon-Hong
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supporting information; experimental part
p. 2828 - 2831
(2011/04/22)
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- Diaminocarbene- and Fischer-carbene complexes of palladium and nickel by oxidative insertion: Preparation, structure, and catalytic activity
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Oxidative insertion of [Pd(PPh3)4] or [Ni(cod) 2]/PPh3 into the C-Cl bond of various 2- chloroimidazolinium- and other -amidinium salts affords metal-diaminocarbene complexes in good to excellent yields. This procedure is complementary to existing methodology in which the central metal does not change its oxidation state, and therefore allows to incorporate carbene fragments that are difficult to access otherwise. The preparation of a variety of achiral as well as enantiomerically pure, chiral metal-NHC complexes (NHC = N-heterocyclic carbene) and metal complexes with acyclic diaminocarbene ligands illustrates this aspect. Furthermore it is shown that oxidative insertion also paves a way to prototype Fischer carbenes of PdII. Since the required starting materials are readily available from urea- or thiourea derivatives, this novel approach allows for substantial structural variations of the ligand backbone. The catalytic performance of the resulting library of nickel- and palladium-carbene complexes has been evaluated by applications to prototype Suzuki-, Heck-, and Kumada-Corriu cross-coupling reactions as well as Buchwald-Hartwig aminations. It was found that even Fischer carbenes show appreciable catalytic activity. Moreover, representative examples of all types of neutral and cationic metal-carbene complexes formed in this study have been characterized by X-ray crystallography.
- Kremzow, Doris,Seidel, Guenter,Lehmann, Christian W.,Fuerstner, Alois
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p. 1833 - 1853
(2007/10/03)
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- Simple preparation of chiral 1,3-dimethyl-2-iminoimidazolidines (monocyclic guanidines) and applications to asymmetric alkylative esterification
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New chiral 1,3-dimethyl-2-iminoimidazolidines (monocyclic guanidines) were simply prepared by the action of primary amines on 2-chloro-1,3- dimethylimidazolinium chlorides, derived from the corresponding urea, in high yields. Modest asymmetric induction i
- Isobe, Toshio,Fukuda, Keiko,Ishikawa, Tsutomu
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p. 1729 - 1735
(2007/10/03)
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