- Propanolysis of arenesulfonyl chlorides: Nucleophilic substitution at sulfonyl sulfur
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We have studied the mechanism of solvolysis of arenesulfonyl chlorides by propan-1-ol and propan-2-ol at 303-323 K. Kinetic profiles were appropriately fit by first-order kinetics. Reactivity increases with electron-donating substituents. Ortho-alkyl substituted derivatives of arenesulfonyl chlorides show increased reactivity, but the origin of this “positive” ortho-effect remains unclear. Likely, ortho-methyl groups restrict rotation around the C-S bond, facilitating the attack of the nucleophile. No relevant reactivity changes have been found with propan-1-ol and propan-2-ol in terms of nucleophile steric effect. The existence of isokinetic relationships for all substrates suggests a single mechanism for the series. Solvolysis reactions of all substrates in both alcohols show isokinetic temperatures (Tiso) close to the working temperature range, which is an evidence of the process being influenced by secondary reactivity factors, likely of steric nature in the TS. Solvation plays a relevant role in this reaction, modulating the reactivity. In some cases, the presence of t-Bu instead of Me in para- position leads to changes in the first solvation shell, increasing the energy of the reaction (ca. 1?kJ·mol?1). The obtained results suggest the same kinetic mechanism of solvolysis of arenesulfonyl chlorides for propan-1-ol and propan-2-ol, as in MeOH and EtOH, where bimolecular nucleophilic substitution (SN2) takes place with nucleophilic solvent assistance of one alcohol molecule and the participation of the solvent network involving solvent molecules of the first solvation shell.
- Iazykov, Mykyta,Canle, Moisés,Santaballa, J. Arturo,Rublova, Ludmila
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supporting information
(2017/09/08)
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- Solvent network at the transition state in the solvolysis of hindered sulfonyl compounds
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Alcoholysis rates of unhindered benzenesulfonyl chlorides (X-ArSO2Cl, X = H-; 4-Br-; 4-Me-) are similar in methanol; the same behavior is also observed in ethanol, whereas the reactivity order in iso-propanol is 4 Me- 2Cl) (X = 2,4,6-Me3-3-NO2-; 2,6-Me2-4-tBu-; 2,4,6-Me3-; 2,3,5,6-Me4-; 2,4,6-iPr3-; 2,4-Me2-; 2,4,6-(OMe)3-) in all studied alcohols show a significant increase in reactivity, the so-called positive steric effect. Most of the substrates showed a reaction order b ~ 2 with respect to the nucleophile in methanol and ethanol, and b ~ 3 in iso-propanol. The correlation between reactivity and the Kirkwood function (1/ξ) gives negative sensitivity (U) for all systems. All substrates showed high sensitivity to media nucleophilicity that depends on ΣσX. Obtained results suggest the alcoholysis of benzenesulfonyl chlorides proceeds through SN2 mechanism where the transition state (TS) involves the participation of 2–3 alcohol molecules; such a TS can be cyclic, in the case of unbranched alcohols, or linear, for alcohols with bulkier hydrocarbon groups like iso-propanol. To include the number of alcohol molecules playing such a role in the TS, the following terminology is proposed: cSN2sn for SN2 reactions involving n solvent molecules in a cyclic (c) TS, where “s” stands for the solvent and “n” is either the closest integer or half-integer to the reaction order relative to the solvent or, in computational studies, the proposed number of solvent molecules taking part in the TS, whereas SN2sn is proposed when the TS is not cyclic. Copyright
- Iazykov, Mykyta,Rublova, Ludmila,Canlel, Moisés,Santaballa, J. Arturo
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- Organocatalytic asymmetric mannich reactions of 5H-oxazol-4-ones: Highly enantio- and diastereoselective synthesis of chiral α-alkylisoserine derivatives
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The first organocatalytic Mannich reaction of 5H-oxazol-4-ones with various readily prepared aryl- and alkylsulfonimides has been developed. Two commercially available pseudoenantiomeric Cinchona alkaloids-derived tertiary amine/ureas have been demonstrated as the most efficient catalysts to access the opposite enantiomers of the Mannich products with equally excellent enantio- and diastereoselectivities. From the Mannich adducts, important α-methyl-α-hydroxy-β-amino acid derivatives, such as the α-methylated C-13 side chain of taxol and taxotere, can be conveniently prepared. Copyright
- Han, Zhiqiang,Yang, Wenguo,Tan, Choon-Hong,Jiang, Zhiyong
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p. 1505 - 1511
(2013/06/27)
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- Phenylenediamine urotensin-II receptor antagonists and CCR-9 antagonists
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The present invention relates to urotensin II receptor antagonists, CCR-9 antagonists, pharmaceutical compositions containing them and their use.
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- Highly Diastereoselective Intermolecular β-Addition of Alkyl Radicals to Chiral 2-(Arylsulfinyl)-2-cycloalkenones
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The diastereoselectivity of intermolecular β-addition of alkyl radicals to 2-(arylsulfinyl)-2-cycloalkenones depends largely upon the structure of the arylsulfinyl group. The reaction of 2-cyclopentenones or 2-cyclohexenones having a sterically bulky arylsulfinyl group such as (3,5-di-tert-butyl-4-methoxyphenyl)sulfinyl, (2,4,6-triisopropylphenyl)sulfinyl or (2,4,6-trimethylphenyl)sulfinyl group gives 3-alkyl-2-(arylsulfinyl)-1-cyclopentanones or 3-alkyl-2-(arylsulfinyl)-1-cyclohexanones in excellent yields and with high diastereoselectivity. Both the X-ray crystallographic analysis and the NOE experiment in the 1H NMR spectrum of (S)-2-[(2,4,6-triisopropylphenyl)sulfinyl]- and (S)-2-[(2,4,6-trimethylphenyl)sulfinyl]-2-cyclopentenone reveal an effective shielding of one of the olefin faces at the β-position by o-isopropyl and o-methyl groups. The addition of bidentate Lewis acids reverses the stereoselection through chelating the intermediates to give the addition products with high diastereoselectivity.
- Mase, Nobuyuki,Watanabe, Yoshihiko,Ueno, Yoshio,Toru, Takeshi
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p. 7794 - 7800
(2007/10/03)
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- The 2,4,6-Triisopropylbenzenesulfonyl Residue, a New Protecting Group for the Guanidino Function of Arginine
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The 2,4,6-triisopropylbenzenesulfonyl group is introduced in high yield into the guanidino function of arginine by the reaction of Nα-protected arginine with 2,4,6-triisopropylbenzenesulfonyl chloride.This protecting group was found to be cleaved by commonly used reagents used in peptide synthesis like methanesulfonic, trifluoromethanesulfonic acid or mixtures of trifluoroacetic with methanesulfonic or trifluoromethanesulfonic acid. - Keywords: Arginine Protecting Group, Arginine-Containing Peptides, Guanidino Function, Peptide Synthesis
- Echner, Hartmut,Voelter, Wolfgang
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p. 1591 - 1594
(2007/10/02)
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- CATALYTIC SULFONYLATION OF PHENOL BY STERICALLY HINDERED SULFONYL CHLORIDES
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The sulfonylation of phenol by substituted arenesulfonyl chlorides XArSO2Cl in the presence of triethylamine in benzene was studied by potentiometric titration.A linear relation was obtained between the logaritmhs of the catalytic rate constants and the steric constants Eso of the substituents in the sulfonyl chloride.The contribution from the induction and steric effects of the substituents at position2 to the kinetics of the process was assessed.It was concluded that the steric effect plays a predominant role over the induction and resonance effects.
- Vizgert, R.V.,Maksimenko, N.N.,Rubleva, L.I.
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p. 2144 - 2146
(2007/10/02)
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