- Rh/Wudaphos-Catalyzed Asymmetric Hydrogenation of Sodium α-Arylethenylsulfonates: A Method to Access Chiral α-Arylethylsulfonic Acids
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A highly enantioselective hydrogenation of various sodium α-arylethenylsulfonates catalyzed by Rh/chiral ferrocenyl bisphosphorus ligand (Wudaphos) was successfully developed to construct a series of chiral α-arylethylsulfonic acids in the presence of CF3SO3H with full conversion and good to excellent enantioselectivity (>99% conversion, up to 96% ee) under mild reaction conditions for the first time. Moreover, the control experiment results showed that the non-covalent ion pair interaction between the α-arylethenylsulfonic acid and the Wudaphos ligand plays an important role in this asymmetric hydrogenation system.
- Yin, Xuguang,Chen, Caiyou,Dong, Xiu-Qin,Zhang, Xumu
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- Application of the extended Grunwald-Winstein equation to the solvolyses of phenyl methanesulfonyl chloride in aqueous binary mixtures
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This report shows the rates of solvolyses for phenyl methanesulfonyl chloride (C6H5CH2SO2Cl, I) in ethanol, methanol, and aqueous binary mixtures incorporating ethanol, methanol, acetone, 2,2,2-trifluroethanol (
- Koh, Han Joong,Kang, Suk Jin
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experimental part
p. 1897 - 1901
(2012/01/14)
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- Competing sulfonylation and phosphonylation following rearrangement of an O-sulfonyl-N-phosphinoylhydroxylamine with tert-butylamine: Demonstration of a phosphonamidic-sulfonic anhydride intermediate and 18O-labelling evidence on how it may be formed
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Reaction of R(Ph)P(O)NHOSO2Bn (R = PhMeCH) with Bu tNH2 in CH2Cl2 gives a mixture of RP(O)(NHPh)NHBut and ButNHSO2Bn, the proportion of the sulfonamide increasing steadily (14.6% to 32.9%) as the concentration of amine is reduced (8.0 to 0.2 mol dm-3). Apparently the phenyl and sulfonate groups in the substrate become transposed, giving a phosphonamidic-sulfonic anhydride RP(O)(NHPh)OSO2Bn which then reacts at the phosphorus or sulfur atom to give the final products; an authentic sample of the anhydride gives similar mixtures of products. Substrate labelled with 18O in the sulfonyl position (57 mol% one 18O atom) gives sulfonamide containing most but not all of the label (43.7 mol% one 18O atom with 2.0 mol dm-3 amine). This implies partial equilibration of the three sulfonate oxygen atoms during rearrangement, or after the anhydride intermediate has been formed.
- Harger, Martin J.P.
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p. 3390 - 3395
(2007/10/03)
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- Active-Site-Directed Modification of Subtilisin
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This paper describes the development of several competitive inhibitors and mechanism-based inactivators of subtilisin BPN′. Various methyl arylakanesulfonates were prepared and shown to be either competitive inhibitors or selective methylating reagents fo
- Zhong, Ziyang,Bibbs, Jeffrey A.,Yuan, Wei,Wong, Chi-Huey
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p. 2259 - 2263
(2007/10/02)
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- Nucleophilic Substitution Reaction of Phenylmethanesulfonyl Halides with Anilines
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Kinetic studies on the nucleophilic substitution reaction of Y-substituted phenylmethanesulfonyl halides with X-substituted anilines in methanol-acetonitrile have been carried out in order to elucidate the reaction mechanism.The phenylmethanesulfonyl fluorides (PSF) had markedly lower rates and smaller magnitudes of ρX and ρY values compared with those for the chlorides (PSC).On the contrary, however, the magnitude of the cross-interaction constant ρXY was greater for PSF than for PSC, so that the degree of bond making in the transition state is actually greater in the reaction of PSF as compared with that for PSC.We have thus demonstrated that extensive charge transfer from a nucleophile to a substrate does not necessarily mean a tight bond in the transition state.Moreover the nonzero ρXY values obtained for both PSC and PSF are taken as evidence in support of a common, associative SN2 mechanism for the two halides.
- Lee, Ikchoon,Kang, Han Keun,Lee, Hai Whang
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p. 7472 - 7477
(2007/10/02)
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- A CAUTIONARY COMMENT ON A RECENT COMMUNICATION ENTITLED "A MEASURE OF CHARGE TRANSFER (ρ) VERSUS A MEASURE OF BOND TIGHTNESS (ρij) IN THE TRANSITION STATE"
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We present evidence that the reaction of anilines with ArCH2SO2Cl and ArCH2SO2F goes mainly via the sulfene (ArCH=SO2) and is not a simple nucleophilic displacement at sulfur, as was assumed in the above paper by I.Lee and H.K.Kang (Tetrahedron Lett. 28, 1183 (1987)), and hence that their conclusions about the interpretation of ρ and ρXY values are unfounded.
- King, J. F.,Skonieczny, S.
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p. 5001 - 5004
(2007/10/02)
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- ALKANESULFONYLATION REACTIONS. I. CHARACTERISTICS OF THE ALKANESULFONYLATION OF PHENOL-d1 AND METHANOL-d1 CATALYZED BY TERTIARY AMINES
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The products from alkanesulfonylation of phenol-d1 and methanol-d1 catalyzed by tertiary amines, which occurs in at least three competing directions (nucleophilic and general base catalysis and a sulfene mechanism), were investigated.The degree of realization of the sulfene mechanism was determined from the content of the ester-d1, and its dependence on the structure of the catalysis, the substrate, the reagent, and the nature of the solvent was investigated.It was shown that the fraction of the ester-d1 decreases with decrease in the basicity and steric accessibility of the tertiary amine.Investigation of the effect of the structure of the sulfonyl chloride shows that the fraction of the sulfene mechanism decreases with decrease in the acidity of the α-protons and their steric accessibility.It was shown that the most favorable conditions for realization of the sulfene mechanism are created in benzene.
- Skrypnik, Yu. G.,Bezrodnyi, V. P.
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p. 511 - 515
(2007/10/02)
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