- Meta C-H Arylation of Electron-Rich Arenes: Reversing the Conventional Site Selectivity
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Controlling site selectivity of C-H activation without using a directing group remains a significant challenge. While Pd(II) catalysts modulated by a mutually repulsive pyridine-type ligand have been shown to favor the relatively electron-rich carbon centers of arenes, reversing the selectivity to favor palladation at the relatively electron-deficient positions has not been possible. Herein we report the first catalytic system that effectively performs meta C-H arylation of a variety of alkoxy aromatics including 2,3-dihydrobenzofuran and chromane with exclusive meta site selectivity, thus reversing the conventional site selectivity governed by native electronic effects. The identification of an effective ligand and modified norbornene (NBE-CO2Me), as well as taking advantage of the statistics, are essential for achieving the exclusive meta selectivity.
- Liu, Luo-Yan,Qiao, Jennifer X.,Yeung, Kap-Sun,Ewing, William R.,Yu, Jin-Quan
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supporting information
p. 14870 - 14877
(2019/10/02)
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- Conversion of thiols into sulfonyl halogenides under aerobic and metal-free conditions
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An environmentally benign, metal-free synthesis of sulfonyl chlorides and bromides from thiols in the presence of ammonium nitrate, an aqueous solution of HCl and HBr and oxygen as a terminal oxidant was developed. The reactivity of various substituted thiophenols, benzylic-, aliphatic- and heteroaromatic thiols was examined. Ammonium nitrate served as a source of nitrogen oxides (NO/NO2), which are the crucial players in a redox-catalytic cycle. Sulfonyl chlorides and bromides were isolated without extraction and "filtered" over a short pad of silica gel; the use of solvents was greatly reduced in comparison with traditional isolation and purification. A "one-pot" protocol for the conversion of thiol into sulfonamide is also demonstrated. Scale-up experiments on the preparation of sulfonyl chloride and bromide are shown. A possible reaction pathway is discussed.
- Jereb, Marjan,Hribernik, Luka
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supporting information
p. 2286 - 2295
(2017/07/24)
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- Aromatic Chlorosulfonylation by Photoredox Catalysis
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Visible-light photoredox catalysis enables the efficient synthesis of arenesulfonyl chlorides from anilines. The new protocol involves the convenient in situ preparation of arenediazonium salts (from anilines) and the reactive gases SO2and HCl (from aqueous SOCl2). The photocatalytic chlorosulfonylation operates at mild conditions (room temperature, acetonitrile/water) with low catalyst loading. Various functional groups are tolerated (e.g., halides, azides, nitro groups, CF3, SF5, esters, heteroarenes). Theoretical and experimental studies support a photoredox-catalysis mechanism.
- Májek, Michal,Neumeier, Michael,Jacobi von Wangelin, Axel
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p. 151 - 155
(2017/01/17)
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- A simple and highly effective oxidative chlorination protocol for the preparation of arenesulfonyl chlorides
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2,4-Dichloro-5,5-dimethylhydantoin (DCDMH) was found to be a mild and efficient reagent for the direct oxidative conversion of sulfur compounds to the corresponding arenesulfonyl chlorides in good to excellent yields through oxidative chlorination. The method is suitable for many types of sulfur substrates (thiols, disulfides, and benzylic sulfides). The overall process is simple, practical, and it provides convenient access to a variety of aryl or heteroarylsulfonyl chlorides. The mild reaction conditions and the broad substrate scope render this method attractive and complementary to existing syntheses of aryl or heteroarylsulfonyl chlorides.
- Pu, Yu-Ming,Christesen, Alan,Ku, Yi-Yin
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supporting information; experimental part
p. 418 - 421
(2010/03/04)
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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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- Bispiperidines as antithrombotic agents
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Novel compounds which are inhibitors of the binding of fibrinogen to the Gp IIb/IIIa platelet receptors, and which can be used therepeutically as antithrombotic agents
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- Elimination of substituted fluoren-9-ylmethyl benzenesulfonates: Hammett substituent effects at a mechanistic borderline
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Rates of elimination of fourteen substituted fluoren-9-ylmethyl benzenesulfonates have been measured in methanolic sodium methoxide and 90% aqueous ethanolic solutions of triethylamine, trimethylamine and 4-methyl morpholine. For the sodium methoxide, a linear Hammett plot with ρ = 0.74, consistent with reaction by an E2 mechanism, is observed. For the amine bases the Hammett plots are curved, suggesting a transition from an E2 mechanism for electron-withdrawing substituents to an irreversible E1cB mechanism with a smaller value of ρ for electron-donating substituents. The evidence for a change of mechanism is weakened by systematic and random deviations of substituents from correlations which span small changes in reactivity (less than ten-fold), by a surprisingly large value of ρ = 2 implied for the concerted (E2) reaction and by the possible influence of negative hyperconjugation. Nevertheless, it is consistent with independent evidence that the borderline between concerted and stepwise mechanisms is associated with chemically distinguishable reaction paths, even though pronounced carbanion character (and probably a small extent of bond-breaking to the leaving group) ensures a degree of similarity of structure and sensitivity to substituents of their transition states.
- Larkin, Finbar G.,More O'Ferrall, Rory A.,Murphy, Donal G.
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p. 1833 - 1848
(2007/10/03)
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- An Improved Synthesis of Arylsulfonyl Chlorides from Aryl Halides
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Arylsulfonyl chlorides 8 are prepared from aryl bromides 5 via lithium arylsulfinates 7 in excellent yields.
- Hamada, Tatsuo,Yonemitsu, Osamu
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p. 852 - 854
(2007/10/02)
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- DISSOCIATION OF SUBSTITUTED BENZENESULPHONAMIDES IN WATER, METHANOL AND ETHANOL
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Thirteen monosubstituted arylsulphonamides (XC6H4SO2NH2) and two 3,4-disubstituted arylsulphonamides (X2C6H3SO2NH2) have been synthetized and their dissociation constants have been measured by potentiometric titration in water, methanol, and ethanol.The Hammett substitution dependences have been calculated for all the media, and changes in the reaction constants due to transition from water to alcohols are discussed in confrontation with analogous dependences of benzoic acids.The reaction constant ρ found in methanol is lower than that in water.The dissociation constants have been treated by the method of the principal components and by multiple linear regression.
- Ludwig, Miroslav,Pytela, Oldrich,Kalfus, Karel,Vecera, Miroslav
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p. 1182 - 1192
(2007/10/02)
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- Process for preparing amides by reaction in presence of molecular sieve
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There is provided a process for preparing amides which comprises reacting an amine, or an amide, and an acid halide, or anhydride, in suitable molecular proportions, in an inert organic diluent, in the presence of an effective amount of a molecular sieve, until the reaction is completed, separating the molecular sieve, and recovering the amide from the organic mother liquor.
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