- Practical and Selective sp3 C?H Bond Chlorination via Aminium Radicals
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The introduction of chlorine atoms into organic molecules is fundamental to the manufacture of industrial chemicals, the elaboration of advanced synthetic intermediates and also the fine-tuning of physicochemical and biological properties of drugs, agrochemicals and polymers. We report here a general and practical photochemical strategy enabling the site-selective chlorination of sp3 C?H bonds. This process exploits the ability of protonated N-chloroamines to serve as aminium radical precursors and also radical chlorinating agents. Upon photochemical initiation, an efficient radical-chain propagation is established allowing the functionalization of a broad range of substrates due to the large number of compatible functionalities. The ability to synergistically maximize both polar and steric effects in the H-atom transfer transition state through appropriate selection of the aminium radical has provided the highest known selectivity in radical sp3 C?H chlorination.
- McMillan, Alastair J.,Sieńkowska, Martyna,Di Lorenzo, Piero,Gransbury, Gemma K.,Chilton, Nicholas F.,Salamone, Michela,Ruffoni, Alessandro,Bietti, Massimo,Leonori, Daniele
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supporting information
p. 7132 - 7139
(2021/03/03)
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- Palladium-Catalyzed Zinc-Amide-Mediated C-H Arylation of Fluoroarenes and Heteroarenes with Aryl Sulfides
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C-H arylation of polyfluoroarenes and heteroarenes with aryl sulfides proceeds smoothly with the aid of a palladium-N-heterocyclic carbene catalyst. A bulky zinc amide, TMPZnCl an effective base to generate the corresponding arylzinc species in situ. This arylation protocol is practically much easier to perform than our previous method, which necessitates preparation of the arylzinc reagents in advance from the corresponding aryl halides. Aryl sulfides that are prepared through sulfur-specific reactions, such as SNAr sulfanylation and extended Pummerer reactions, undergo this direct arylation, offering interesting transformations that are otherwise difficult to achieve with conventional halogen-based organic synthesis.
- Otsuka, Shinya,Yorimitsu, Hideki,Osuka, Atsuhiro
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supporting information
p. 14703 - 14707
(2015/10/20)
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- 2,2,6,6-Tetramethylpiperidine-catalyzed, ortho-selective chlorination of phenols by sulfuryl chloride
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2,2,6,6-Tetramethylpiperidine (TMP)-catalyzed (1- 10%) chlorinations of phenols by SO2Cl2 in aromatic solvents are more ortho selective than with primary and less hindered secondary amine catalysts. Ortho-selective chlorination is successful even with electron deficient phenols such as 2-hydroxybenzaldehyde and 2'- hydroxyacetophenone. Notably, ortho selectivity increases with the reaction temperature. On the other hand, tetraalkylammonium chloride-catalyzed chlorinations are moderately para selective.
- Saper, Noam I.,Snider, Barry B.
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p. 809 - 813
(2014/04/03)
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- PROCESS FOR PREPARING CHLOROAMINES
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The present application relates to a process for preparing chloroamines which can be used as precursors for syntheses of fine chemicals and active ingredients from pharmaceuticals and/or agriculture, by reaction of secondary amines of the formula (II) with chlorine gas in the presence of an aqueous alkali metal or alkaline earth metal oxide base.
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Page/Page column 8
(2013/08/28)
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- Mechanism of electrochemical oxidation of 1-chloro-2,2,6,6- tetramethylpiperidine
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In contrast to 2,2,6,6-tetramethylpiperidine and other aliphatic amines, at the electrochemical oxidation of 1-chloro-2,2,6,6-tetramethylpiperidine a sufficiently stable cation-radical is formed. Its formation is confirmed by the data of cyclic voltammetry and electron paramagnetic resonance. Further transformation of the cation-radical leads to the formation of 2,2,6,6-tetramethylpiperidin-1-oxyl.
- Kagan,Yanilkin,Morozov,Nastapova,Zhukova,Kashparov,Kashparova
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scheme or table
p. 1001 - 1003
(2011/04/16)
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- ELECTROCHEMICAL CHLORINATION AND BROMINATION OF DERIVATIVES OF 2,2,6,6-TETRAMETHYLPIPERIDINE
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It was shown that the direction of electrochemical chlorination and bromination in the derivatives of 2,2,6,6-tetramethylpiperidine depends on the acidity of the medium.In an acidic medium 3,5-dibromo-4-oxo-2,2,6,6-tetramethylpiperidine and 3,3,5,6-tetrachloro-4-oxo-2,2,6,6-tetramethylpiperidine respectively are formed from 4-oxo-2,2,6,6-tetramethylpiperidine; derivatives of 2,2,6,6-tetramethylpiperidine not containing a carbonyl group form perbromides during bromination under these conditions.Electrochemical chlorination and bromination in a neutral medium lead to the corresponding N-halogeno derivatives.It was established that 3,3,5,5-tetrachloro-4-oxo-2,2,6,6-tetramethylpiperidine enters into the Favorskii rearrangement with the formation of 3-hydroxy-4-oxo-2,2,5,5-tetramethylpyrrolidine-3-carboxamide.
- Zhukova, I. Yu.,Pozhidaeva, S. A.,Kagan, E. Sh.,Smirnov, V. A.
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p. 626 - 631
(2007/10/02)
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- Kinetics and mechanism of chlorine exchange between chloramine-T and secondary amines
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The kinetics and mechanisms of chlorine transfer from chloramine-T (CAT) to several amines are second order and independent of p-toluenesulfonamide concentration; thus, the reaction does not involve disproportionation of CAT to dichloramine-T. From the profile of pH versus rate, the following mechanisms were proposed: (1) reaction of the ionized species of CAT with the ionized amine (ionic mechanism) and (2) reaction of the un-ionized species of CAT with the un-ionized amine (nonionic mechanism). The second-order, pH- independent rate constants calculated for the ionic and nonionic mechanisms were 1.6 and 5 x 106 M-1 s-1, respectively. Although these two mechanisms are kinetically indistinguishable, the rate constant for the nonionic mechanism is of the same order of magnitude as those calculated for similar chlorination reactions involving nonionizable chloramines, such as N- chlorosuccinimide, N-chloroquinuclidine, and N-chloro-N- methylbenzenesulfonamide. The proposed mechanism for the chlorine exchange involves a molecule of water in a cyclic, six-membered transition state.
- Dannan,Crooks,Dittert,Hussain
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p. 652 - 656
(2007/10/02)
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- A SIMPLE METHOD FOR THE SYNTHESIS OF THE STERICALLY HINDERED CHLORAMINES
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A simple route to the hindered chloramines, starting from the corresponding hindered amines is reported.Sodium dichlorisocyanurate is the chlorinating agent.
- Zakrzewski, Jerzy
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p. 2135 - 2140
(2007/10/02)
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