- Asymmetric o-to-c aryloxycarbonyl migration of indolyl carbonates using single-handed dynamic helical polyquinoxalines bearing 4-aminopyridyl groups as chiral nucleophilic catalysts
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Use of single-handed dynamic helical macromolecules as nucleophilic catalysts in asymmetric Steglich-type O-to-C aryloxycarbonyl rearrangement of 3-substituted indol-2-yl aryl carbonates is demonstrated. Among several single-handed poly-(quinoxaline-2,3-diyl) copolymers (PQXap) bearing achiral 4-aminopyridin-3-yl groups at the 5-position of the quinoxaline rings, PQXmdpp and PQXapy, containing N-methylpyrrolidine-fused pyridin-3-yl and 4-(1-azetidinyl)pyridin-3-yl groups, respectively, showed higher enantioselectivity and catalytic activity than PQXdmap, bearing 4-dimethylamino-pyridine-3-yl groups. Substrates bearing p-(trifluoromethyl)phenyloxycarbonyl groups on both the nitrogen and oxygen atoms showed high reactivity, giving oxindoles with a quaternary stereogenic carbon center at their 3-positions in up to 97:3 enantiomeric ratio in THF. The macromolecular catalysts underwent inversion of their helix sense by solvent effect, allowing the same catalyst to give the opposite enantiomer in a mixture of methyl t-butyl ether and 1,1,2-trichloroethane (3:1). The macromolecular catalysts could be easily recovered by adding acetonitrile to the reaction mixture and were reused four times without reduction in enantioselectivity.
- Yamamoto, Takeshi,Takahashi, Takuya,Murakami, Ryo,Ariki, Naoto,Suginome, Michinori
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supporting information
p. 943 - 949
(2021/04/29)
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- Versatile Cp*Co(III)(LX) Catalyst System for Selective Intramolecular C-H Amidation Reactions
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Herein, we report the development of a tailored cobalt catalyst system of Cp*Co(III)(LX) toward intramolecular C-H nitrene insertion of azidoformates to afford cyclic carbamates. The cobalt complexes were easy to prepare and bench-stable, thus offering a convenient reaction protocol. The catalytic reactivity was significantly improved by the electronic tuning of the bidentate LX ligands, and the observed regioselectivity was rationalized by the conformational analysis and DFT calculations of the transition states. The superior performance of the newly developed cobalt catalyst system could be broadly applied to both C(sp2)-H and C(sp3)-H carbamation reactions under mild conditions.
- Chang, Sukbok,Jung, Hoimin,Kim, Dongwook,Lee, Jeonghyo,Lee, Jia,Park, Juhyeon
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supporting information
p. 12324 - 12332
(2020/08/06)
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- KINETICS AND MECHANISM OF THE CATALYTIC PHOSGENATION OF PHENOLS. II. PHOSGENATION OF 1-NAPHTHOL IN THE PRESENCE OF PYRIDINE 1-OXIDES
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Pyridine N-oxides are effective catalysts for the phosgenation of 1-naphthol and surpass tetramethylurea in their activity.Investigation of the kinetics of the process in dichloromethane showed that the reaction takes place by a mechanism of nucleophilic catalysis, where the active acylating agent is a 1:1 complex of the N-oxide with phosgene, while the thermodynamically more stable 2:1 complex is inactive.Increase in the nucleophilicity of the N-oxide, on the one hand, leads to stabilization of the 1:1 complex and , on the other to a reduction in its activity.
- Grabarnik, M. S.,Chimishkyan, A. L.,Orlov, S. I.
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p. 1840 - 1844
(2007/10/02)
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- KINETICS AND MECHANISM OF THE CATALYTIC PHOSGENATION OF PHENOLS. I. PHOSGENATION OF 1-NAPHTHOL IN THE PRESENCE OF TETRAMETHYLUREA
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The kinetic relationships governing the phosgenation of 1-naphthol in the presence of tetramethylurea and its reaction with phosgene were investigated.Phosgene reacts reversibly with tetramethylurea to form 1:1 and 1:2 complexes, and the latter is inactive as acylating agent.The obtained results indicate that the phosgenation of 1-naphthol under the given conditions takes place by a mechanism of nucleophilic catalysis.
- Grabarnik, M. S.,Chimishkyan, A. L.,Orlov, S. I.,Shebeko, S. M.,Salmin, A. L.
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p. 2166 - 2173
(2007/10/02)
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- 1-Aziridine carboxylic acid derivatives with immunostimulant activity
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2-Substituted-1-aziridine-carboxylic acid esters exhibiting immuno-stimulant activity and of the formula STR1 wherein X is a carbamoyl or alkoxycarbonyl radical, and R1 is an aliphatic hydrocarbon radical optionally substituted by halogen, alkoxy, amino, carbamoyloxy, cycloalkyl, hydroxyl, an imido or heterocyclic radical, cycloalkyl; or aryl, aralkyl, aryloxyalkyl or arylthioalkyl wherein the aryl moiety is optionally substituted by halogen, alkyl, alkoxy, hydroxyl, amino, nitro, cyano, acyl, carbalkoxy, thioalkyl, alkylsulphonyl, phenyl or trifluoromethyl. Counterparts where X is --CN and R1 is as above, except for ethyl, are also new.
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