- Palladium-Catalyzed C-H Silylation of Aliphatic Ketones Using an Aminooxyamide Auxiliary
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A palladium-catalyzed β-C(sp3)-H silylation of aliphatic ketones with disilanes to afford β-silyl ketones is reported. The aminooxyamide auxiliary is critical for the C-H activation and silylation. The reaction tolerates a number of functional groups and
- Jiang, Chao,Li, Jianhua
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- Palladium-Catalyzed ortho-C(sp2)-H Silylation of Aromatic Ketones Using an Aminooxyamide Auxiliary
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A palladium-catalyzed direct and selective ortho-C(sp2)-H silylation of aromatic ketones has been achieved using an aminooxyamide auxiliary. The reaction tolerates various orth-, meta-, and para- substituents on the aromatic ring and can be applied to thi
- Li, Jianhua,Ding, Meiying,Jiang, Chao
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supporting information
p. 9036 - 9040
(2021/11/24)
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- Hydrogen Bond Directed Photocatalytic Hydrodefluorination: Overcoming Electronic Control
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The photocatalytic C-F functionalization of highly fluorinated arenes is a powerful method for accessing functionalized multifluorinated arenes. The decisive step in the determining regioselectivity in fluorine functionalization is fluoride fragmentation from the radical anion of the multifluorinated arene. To date, the availability of regioisomers has been dictated by the innate electronics of the fluorinated arene, limiting the synthetic utility of the chemistry. This study investigates the remarkable ability of a strategically located hydrogen bond to transcend the normal regioselectivity of the C-F functionalization event. A significant rate acceleration is additionally observed for hydrodefluorination of fluorines that can undergo intramolecular hydrogen bonds that form 5-8-membered cycles with moderately acidic N-H's. The hydrogen bond is expected to facilitate the fragmentation not only by bending the C-F bond of the radical anion out of planarity but also by increasing the exothermicity of the fluoride extrusion step through protonation of the naked fluoride. Finally, the synthetic utility of the method is demonstrated in an expedited synthesis of the trifluorinated α-phenyl acetic acid derivative required for the commercial synthesis of Januvia, an antidiabetic drug. This represents the first synthesis of a commercially important multifluorinated arene via a defluorination strategy and is significantly shorter than the current strategy.
- Khaled, Mohammad B.,El Mokadem, Roukaya K.,Weaver, Jimmie D.
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supporting information
p. 13092 - 13101
(2017/09/26)
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- General and efficient synthesis of polyfluorinated 2-aminotolans and 2-arylindoles
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It was established here that cross-coupling of polyfluorinated 2-iodoanilines with arylacetylenes in MeCN in the presence catalytic amounts of Pd(PPh3)2Cl2, CuI and Et3N produces the corresponding 2-aminotolans although their yields are decreased from 98% to 40% with increasing fluorination of the substrates. It was shown that the 2-aminotolans with six or fewer fluorine atoms in their rings can be heterocyclised by heating in ethanol containing p-TSA to produce the corresponding polyfluorinated indoles. Cyclisation of tolans containing larger numbers of fluorine atoms in their rings proceeds most efficiently in the presence of KOH, resulting in 2-phenylindoles containing the current maximum of eight fluorine atoms.
- Politanskaya, Larisa V.,Shteingarts, Vitalij D.,Tretyakov, Evgeny V.
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- PALLADIUM(II)-CATALYZED SELECTIVE FLUORINATION OF BENZOIC ACIDS AND DERIVATIVES
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A new method of ortho-fluorination for selectively fluorinating a benzoic acid or derivative compound where an aryl C—H bond is directly replaced by an aryl C—F bond is provided. The method comprises reacting a compound having the formula: wherein X is at
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Paragraph 0135; 0136
(2014/02/16)
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- Continuous flow synthesis of difluoroamine systems by direct fluorination
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Continuous flow methodology for the synthesis of perfluoroaryl difluoroamine derivatives by reaction of fluorine gas with an appropriate perfluoroaniline substrate is described, further demonstrating the efficient use of flow regimes for reactions involvi
- McPake, Christopher B.,Murray, Christopher B.,Sandford, Graham
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p. 145 - 150
(2013/04/10)
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- Pd(II)-catalyzed cross-coupling of C(sp2)h bonds and alkyl, aryl, and vinylboron reagents via Pd(II)/Pd(0) catalysis
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Pd(II)-catalyzed cross-coupling of ortho-CH bonds in benzoic acid and phenylacetic acid amides with alkyl, aryl, and vinylboron reagents have been achieved via Pd(II)/Pd(0) catalysis, demonstrating the unprecedented versatility of CH activation reactions.
- Wasa, Masayuki,Chan, Kelvin S. L.,Yu, Jin-Quan
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supporting information; experimental part
p. 1004 - 1006
(2011/12/05)
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- Palladium(II)-catalyzed selective monofluorination of benzoic acids using a practical auxiliary: A weak-coordination approach
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Finally, a choice! A highly selective palladium(II)-catalyzed ortho-monofluorination reaction has been achieved for the first time through a weak coordination (see scheme; Ar=2,3,5,6-tetrafluoro-4-(trifluoromethyl)phenyl) . Simple modification of this protocol allows for a choice between mono- and difluorination. The mono- and difluorinated benzoic acid derivatives are valuable in the pharmaceutical and agrochemical industries. Copyright
- Chan, Kelvin S. L.,Wasa, Masayuki,Wang, Xisheng,Yu, Jin-Quan
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supporting information; experimental part
p. 9081 - 9084
(2011/10/17)
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- Mechanisms of reactions of halogenated compounds. Part 7. Effects of fluorine and other groups as substituents on nucleophilic aromatic substitution
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The effect of fluorine as a substituent group on nucleophilic aromatic substitution is discussed, where a fluorine atom located ortho to the point of substitution may be of variable activating influence, whereas fluorine located para is slightly deactivat
- Chambers, Richard D.,Martin, Peter A.,Sandford, Graham,Williams, D. Lyn H.
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scheme or table
p. 998 - 1002
(2009/04/04)
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- Synthesis of vinylsulfanyl-substitued polyfluorobenzenes from perfluorotoluene
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The reaction of octafluorotoluene in DMF with vinylthiolate ion generated from divinyl sulfide by the action of sodium in liquid ammonia afforded 2,3,5,6-tetrafluoro-4-trifluoromethylaniline, 3,6-difluoro-4-trifluoromethyl-1, 2,5-tris(vinylsulfanyl)benzen
- Amosova,Gavrilova,Afonin
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p. 402 - 405
(2007/10/03)
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- Fluorinated 1,3λ4δ2,2,4-benzodithiadiazines - A synthetic, structural and theoretical study
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The series of title compounds has been prepared through both electrophilic (C6HnF5-n-N=S=N-SiMe3 + SCl2) and nucleophilic (C6HF4_S-N=S=N-SiMe3 + CsF) intramolecular ortho-cyclisation reactions, and the former route seems to be the more effective. High regioselectivity of the ring-closing procedures is observed in both cases. The compounds were characterised by X-ray crystallography and multinuclear (1H, 13C, 15N and 19F) NMR spectroscopy. In accordance with GIAO calculations, 15N{1H} experiments and the effects observed on complete substitution of hydrogen by fluorine, the high-field signal in the 15N NMR spectra can be assigned to N-4 and the low-field signal to N-2. In the crystal, 5,6,7-trifluoro-(5) and 5,6,8-trifluoro-1,3λ4δ22,4- benzodithiadiazine (6) are planar, whereas the 6,8-difluoro derivative 3 is bent along the S1...N4 line by 8.3°. According to NICS calculations the heterocycle moiety in this compound class is antiaromatic while the carbocycle is aromatic. The fluorine substituents increase the aromaticity - and in some cases (especially when a fluorine atom is present in the 8-position) the antiaromaticity - of the corresponding rings. The ortho-fluoro-containing starting material C6HnF5-n-N=S=N-SiMe3 (n = 2: 10) cyclises to the fluorinated 2,1,3-benzothiadiazole 27 upon treatment with CsF instead of SCl2. For starting compound 6-HC6F4-S-N=S=N-SiMe3 (14) the planar (Z,E) configuration features a short intramolecular H...N contact, as evidenced by X-ray diffraction. Both the reaction pathways mentioned are also discussed. Wiley-VCH Verlag GmbH, 69451 Weinheim, Germany, 2003.
- Makarov, Alexander Yu.,Bagryanskaya, Irina Yu.,Blockhuys, Frank,Van Alsenoy, Christian,Gatilov, Yuri V.,Knyazev, Vladimir V.,Maksimov, Alexander M.,Mikhalina, Tatiana V.,Platonov, Vyacheslav E.,Shakirov, Makhmut M.,Zibarev, Andrey V.
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- Reactions of polyfluoroarenes with hexamethyldisilazane and with 1,1,1-trimethyl-N,N-bis(trimethylsilyl)stannaneamine in the presence of caesium fluoride
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Hexamethyldisilazane and 1,1,1-trimethyl-N,N-bis(trimethylsilyl)stannaneamine aminate pentafluoropyridine, octafluorotoluene, pentafluorobenzonitrile, pentafluoronitrobenzene and pentafluorobenzene sulphonyl fluoride in the presence of caesium fluoride with formation of the corresponding perfluorinated aryl amines (ArNH2), diarylamines (Ar2NH) and triarylamines (Ar3N) (where the amine functions are in positions 4 relative to the arene substituent). - Keywords: Polyfluoroarenes; Hexamethyldisilazane; Caesium fluoride; Silylated amines
- Miller, Alexey O.,Furin, Georgii G.
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p. 169 - 172
(2007/10/03)
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- REACTION OF AROMATIC COMPOUNDS WITH NUCLEOPHILIC REAGENTS IN LIQUID AMMONIA. X. AMINATION OF POLYFLUORINATED AROMATIC COMPOUNDS CONTAINING ELECTRON-WITHDRAWING SUBSTITUENTS
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It was shown for the case of 2,4-difluoro-, 2,4,6-trifluoro-, and pentafluoronitrobenzenes that both liquid ammonia and sodium amide in liquid ammonia are effective reagents for aminodefluorination with respect to the fluorine derivatives of nitrobenzene.The observed tendency for the ortho-orientation with respect to the nitro group to change to para-orientation with increase in the number of fluorine atoms is more clearly defined for sodium amide than for liquid ammonia as nucleophile on account, clearly, of the stabilization of the transition state of ortho-substitution in the latter case by an intramolcular hydrogen bond.
- Selivanova, G. A.,Chuikova, T. V.,Shtark, A. A.,Shteingarts, V. D.
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p. 2267 - 2272
(2007/10/02)
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- N-(POLYFLUOROARYL)-HIDROXYLAMINES. SYNTHESIS AND PROPERTIES
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Fluorine-containing N-arylhydroxylamines have been obtained by the reaction of hydroxylamine or its N- and O-derivatives on polyfluorinated benzenes and pentafluoropyridine.The influence of fluorine atoms on the reactivity of hydroxylamino group has been investigated.The reaction of N-polyflouroarylhydroxylamines with aldehydes has been shown not to occur, whereas their reaction with nitrosobenzenes leads to azoxybenzenes and with Lewis acids leads to corresponding nitrosobenzenes, azoxybenzenes and anilines.The action of acids on 2,3,5,6-tetrafluorophenylhydroxylamine leads to the acid-catalyzed rearrangement of the latter into 4-amino-2,3,5,6-tetrafluorophenol.C,N-Diarylnitrones have been obtained by the oxidation with MnO2 of fluorine-containing arylhydroxylamines possessing the CH-fragment in an α-position.
- Miller, A.O.,Furin, G. G.
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p. 247 - 272
(2007/10/02)
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- MECHANISM FOR REACTIONS OF HALOGENATED COMPOUNDS. PART 4. ACTIVATING INFLUENCES OF RING-NITROGEN AND TRIFLUOROMETHYL IN NUCLEOPHILIC AROMATIC SUBSTITUTION
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Rate constants have been measured for the reactions of ammonia with various fluorinated pyridines and diazines in aqueous dioxan at 25 deg C.From the results the activating effects of ring-nitrogen (relative to C-H) and of trifluoromethyl (relative to -H)
- Chambers, R. D.,Martin, P. A.,Waterhouse, J. S.,Williams, D. L. H.,Anderson, B.
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p. 507 - 514
(2007/10/02)
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