- Long sought synthesis of quaternary phosphonium salts from phosphine oxides: Inverse reactivity approach
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Quaternary phosphonium salts (QPS), a key class of organophosphorus compounds, have previously only been available by routes involving nucleophilic phosphorus. We report the realisation of the opposite approach to QPS utilising phosphine oxides as the electrophilic partner and Grignard reagents as nucleophiles. The process is enabled through the crucial intermediacy of the derived halophosphonium salts. The route does not suffer from the slow kinetics and limited availability of many parent phosphines and a broad range of QPS were prepared in excellent yields.
- Vetter, Anna C.,Nikitin, Kirill,Gilheany, Declan G.
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supporting information
p. 5843 - 5846
(2018/06/13)
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- Visible Light-Induced Oxidative Chlorination of Alkyl sp3 C-H Bonds with NaCl/Oxone at Room Temperature
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A visible light-induced monochlorination of cyclohexane with sodium chloride (5:1) has been successfully accomplished to afford chlorocyclohexane in excellent yield by using Oxone as the oxidant in H2O/CF3CH2OH at room temperature. Other secondary and primary alkyl sp3 C-H bonds of cycloalkanes and functional branch/linear alkanes can also be chlorinated, respectively, under similar conditions. The selection of a suitable organic solvent is crucial in these efficient radical chlorinations of alkanes in two-phase solutions. It is studied further by the achievement of high chemoselectivity in the chlorination of the benzyl sp3 C-H bond or the aryl sp2 C-H bond of toluene.
- Zhao, Mengdi,Lu, Wenjun
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supporting information
p. 4560 - 4563
(2017/09/11)
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- Oxidative C-C bond formation reactivity of organometallic Ni(II), Ni(III), and Ni(IV) complexes
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The use of the tridentate ligand 1,4,7-trimethyl-1,4,7-triazacyclononane (Me3tacn) and the cyclic alkyl/aryl C-donor ligand-CH2CMe2-o-C6H4-(cycloneophyl) allows for the synthesis of isolable organometallic NiII, NiIII, and NiIV complexes. Surprisingly, the fivecoordinate NiIII complex is stable both in solution and the solid state, and exhibits limited C-C bond formation reactivity. Oxidation by one electron of this NiIII species generates a six-coordinate NiIV complex, with an acetonitrile molecule bound to Ni. Interestingly, illumination of the NiIV complex with blue LEDs results in rapid formation of the cyclic C-C product at room temperature. This reactivity has important implications for the recently developed dual Ni/photoredox catalytic systems proposed to involve high-valent organometallic Ni intermediates. Additional reactivity studies show the corresponding NiII species undergoes oxidative addition with alkyl halides, as well as rapid oxidation by O2, to generate detectable NiIII and/or NiIV intermediates and followed by C-C bond formation.
- Watson, Michael B.,Rath, Nigam P.,Mirica, Liviu M.
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- Ketone-catalyzed photochemical C(sp3)–H chlorination
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Photoexcited arylketones catalyze the direct chlorination of C(sp3)–H groups by N- chlorosuccinimide. Acetophenone is the most effective catalyst for functionalization of unactivated C–H groups while benzophenone provides better yields for benzylic C–H functionalization. Activation of both acetophenone and benzophenone can be achieved by irradiation with a household compact fluorescent lamp. This light-dependent reaction provides a better control of the reaction as compared to the traditional chlorination methods that proceed through a free radical chain propagation mechanism.
- Han, Lei,Xia, Ji-Bao,You, Lin,Chen, Chuo
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p. 3696 - 3701
(2017/06/13)
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- Regio-selective synthesis of key intermediates of fexofenadine
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The present work is focused on improved process of preparation of fexofenadine which is achieved by regio-selective synthesis of intermediate; 1-oxoalkoxy-2-methyl-2-[4-(4-chloro-1-oxobutyl)phenyl]propane. The said intermediate is prepared in good yields and with greater purity wherein the synthesis of side products like 1-oxoalkoxy-2-methyl-2-[3-(4-chloro-1-oxobutyl)phenyl]propane (metaisomer) is reduced to a great amount. The intermediate, 1-oxoalkoxy-2-methyl-2-[4-(4-chloro-1-oxobutyl)phenyl]propane (para-isomer) where, alkyl group is selected from C2-5 carbon chain, is synthesized through preparation of 1-chloro-2-methyl-2-phenylpropane which upon reaction with potassium salt of aliphatic carboxylic acid followed by Friedel-Crafts acylation with 4-chlorobutyrylchloride results into desired intermediate, 1-oxoalkoxy-2-methyl-2-[4-(4-chloro-1-oxobutyl)phenyl]propane and a side impurity, 1-oxoalkoxy-2-methyl-2-[3-(4-chloro-1-oxobutyl)phenyl]propane (meta-isomer) in the ratio of 1:0.09-0.15. The above said mixture can be directly used for the synthesis of fexofenadine and has an advantage of eliminating the purification process at intermediate stage and use of less volume of expensive solvents.
- Kumar, Anil,Bhashkar, Bhuwan,Kumar, Harish,Singh, Gurpreet
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p. 2285 - 2287
(2015/12/19)
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- A process for producing 4-(4-halo-1-oxybutyl)-alpha,alpha-dimethylbenzene acetic acid or alkyl esters thereof
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Disclosed herein is a process for large scale production of pure 4-(4-halo-1-oxybutyl)-α,α-dimethylbenzene acetic acid or alkyl esters thereof, wherein the process comprises of condensing (2-halo-1,1-dimethyl-ethyl)benzene with acetate salt followed by acylation with ω-halo compound, hydrolyzing and cyclizing the resultant regioisomers, subsequently oxidizing and purifying to obtain pure regioisomer, further halogenating and/or esterifying the para regioisomer to produce 4-(4-halo-1-oxybutyl)-α,α-dimethylbenzene acetic acid or their alkyl esters.
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Page/Page column 7
(2011/04/14)
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- Chlorination of various substrates in subcritical carbon tetrachloride
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Various aliphatic hydrocarbons and the side chains of aromatic hydrocarbons were chlorinated in subcritical carbon tetrachloride. Chlorination of aromatic compounds including 1,4-disubstituted benzenes was investigated. Ketones and sulfones were stable under the employed conditions. Sulfoxides were converted into sulfides in a low to modest yields. The coupling adducts between olefins and carbon tetrachloride were obtained from the reactions of olefins.
- Tanemura, Kiyoshi,Suzuki, Tsuneo,Nishida, Yoko,Horaguchi, Takaaki
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experimental part
p. 2881 - 2888
(2010/06/16)
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- Synthesis of ethophenprox
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An ethophenprox synthesis from easily available p-nitroneophyl chloride was developed. The reduction of the latter to aniline derivative followed by Sandmayer's and Claisen's reactions furnished p-ethoxyneophyl chloride that by condensation with 3-phenoxybenzyl alcohol in the presence KOH in DMSO yielded ethophenprox.
- Rakhimov,Galin,Tomilov,Le
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p. 1629 - 1634
(2007/10/03)
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- Mechanistic study of the reaction of 1,1-dihalo-2-methyl-2-phenylpropanes with LDA. Evidence for radical and carbene pathways
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An attempt was made to determine the mechanisms involved in the reactions of the model systems 1,1-dichloro-2-methyl-2-phenylpropane (1) and 1,1-diiodo-2-methyl-2-phenylpropane (2) with LDA.These systems were chosen as ones capable of providing evidence for the formation of radical as well as carbene products.The techniques employed in investigating the mechanistic features of these reactions involved studying the effect of the leaving group, the effect of radical and carbene trapping agents on the product distribution, and isotopic tracer experiments using labeled solvent (THF-d8) and nucleophile (LDA-d2).The major product of the reaction of the geminal dichloride (1) is thought to be derived from a chlorocarbene, whereas the geminal diiodide (2) appears to form products derived from both carbene and radical intermediates.On the basis of the results of radical trapping experiments and those of deuterium-labeling experiments, evidence is presented to support the notion that products A, E, and H are derived from a radical precursor.In addition, products A and H are also believed to be formed from the vinilyc halide D (or B) and the monoiodide E, respectively.Reasonable mechanisms for the formation of the other products formed in these reactions have been proposed on the basis of the available data.
- Ashby, E. C.,Mehdizadeh, Ali,Deshpande, Abhay K.
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p. 1322 - 1330
(2007/10/03)
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- Versatility of Zeolites as Catalysts for Ring or Side-Chain Aromatic Chlorinations by Sulfuryl Chloride
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Zeolites catalyze chlorination of aromatics by sulfuryl chloride SO2Cl2.It is possible by an appropriate choice of the catalyst to effect at will, with very high selectivity, either the ring or the side-chain chlorination.Zeolite ZF520 is the choice catalyst for the former, because of its high Broensted acidity.Zeolite NaX (13X) is a fine catalyst for the latter, free-radical chlorination; the reaction is best effected in the presence of a light source; the catalyst can be reused many times with no loss in activity.Both reaction modes, the ionic (ring chlorination)and the radical (side-chain substitution), are likely to occur outside of the channel network in the microporous solid.The effects of various experimental factors - such as the nature of the solvent, the reaction time and temperature, the Broensted acidity of the solid support, the presence of radical inhibitors, and the quantity of catalysts - were investigated.The procedures resulting from this study are very easy to implement in practice and are quite effective.
- Delaude, Lionel,Laszlo, Pierre
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p. 5260 - 5269
(2007/10/02)
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- REACTIONS OF BrCl WITH ALKYL RADICALS.
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It is demonstrated that photohalogenation of low reactivity substrates with BrCl occurs mainly with Cl. selectivity.With tertiary or benzylic hydrogens in the substrate, mainly Br. selectivity is observed.These observations are rationalized, taking into account the relative concentrations of halogen atoms and their respective rates of hydrogen abstractions.The resultant radicals react with BrCl to make (RBr/RCl) in ratios between 1 and 15.
- Skell, P. S.,Baxter, H. N.,Tanko, J. M.
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p. 5181 - 5184
(2007/10/02)
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- Kinetics of the 1,2-Migration of Carbon-Centered Groups in 2-Substituted 2,2-Dimethylethyl Radicals
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The rearrangements RCMe2CH2. -> RCH2C.Me2 (kr) (R = Ph, Me3CCC, Me3CC=O, and NC) have been studied over a range of temperatures by product analyses with use of the common competiting reaction RCMe2CH2. + CCl4 -> RCMe2CH2Cl + CCl3. (kCl).For R = H2C=CH the rearrangement was so fast that only the rearranged chloride, RCH2CMe2Cl, was produced.All these rearrangements occur via a 3-membered cyclic intermediate radical (or transition state).Various considerations led to the following Arrhenius equation for chlorine abstraction: log (kCl/M-1 s-1)=(8.14 +/- 0.42)-(5.52 +/- 0.63)/τ, where τ=2.3RT kcal/mol, and this equation is used to calculate Arrhenius parameters for migration of all but the H2C=CH group.Comparison of these parameters with those already available from kinetic EPR measurements leads to a choice of preferred Arrhenius parameters for all five rearrangements.The cyano group had an unexpectedly low mobility while the pivaloyl group underwent a surprisingly rapid 1,2-shift.Migratory aptitudes increase along the series R = NC C r at 25 deg C = 0.9, 93, 762, 1.7*105, and 1.0 * 107 s-1, respectively.The preferred pre-exponential factors all lie in the range 1010.9 - 1012.0, while the activation energies vary from 16.4 kcal/mol for R = NC to 5.7 kcal/mol for R = H2C=CH.These results are discussed in relation to the results of thermochemical kinetic calculations and to earlier work on the 1,2-migration of unsaturated groups in radicals.
- Lindsay, D. A.,Lusztyk, J.,Ingold, K. U.
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p. 7087 - 7093
(2007/10/02)
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- Catalytic Replacement of Unactivated Alkane Carbon-Hydrogen Bonds with Carbon-X Bonds (X = Nitrogen, Oxygen, Chlorine, Bromine, or Iodine). Coupling of Intermolecular Hydrocarbon Activation by MnIIITPPX Complexes with Phase-Transfer Catalysis
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A simple system has been devised to facilitate the first processes for the catalytic replacement of unactivated alkane C-H bonds with C-X bonds, X = nitrogen and iodine.The system also enables alkane C-H bonds to be replaced by C-X bonds, X = chlorine, bromine, and oxygen.The system is composed of two liquid phases and the oxidant iodosylbenzene (iodosobenzene).The alkane substrate, the MnIIITPPX catalyst, and the organic solvent (dichloromethane, chlorobenzene, or other aromatic hydrocarbon) constitute one phase, a saturated aqueous solution of the sodium salt of the anion to be incorporated into the alkane, NaX, X = N3(1-), NCO(1-), I(1-), Br(1-), or Cl(1-), constitutes the second phase, and the sparingly soluble oxidant iodosylbenzene constitutes a third phase.When the two liquid phases and the oxidant iodosylbenzene are stirred under an inert atmosphere, both RX and ROH products are produced catalytically based on MnTPP and in reasonable yield based on iodosylbenzene.The MnTPP moiety functions as a catalyst for C-H bond cleavage and for phase transfer of X(1-) from the aqueous phase to the organic phase where the functionalization chemistry takes place.The oxidant hypochlorite can be used in place of, but is less effective than, iodosylbenzene, and the oxidants hydrogen peroxide, periodate, and persulfate are ineffective.Product distributions obtained from the oxidation of cyclohexane, isobutane, 2,3-dimethylbutane, and tert-butylbenzene are most consistent with a product-determining step that involves transfer of X from manganese to a free alkyl radical intermediate.
- Hill, Craig L.,Smegal, John A.,Henly, Timothy J.
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p. 3277 - 3281
(2007/10/02)
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- Hydrocarbon Functionalization by the (Iodosylbenzene)manganese(IV) Porphyrin Complexes from the (Tetraphenylporphinato)manganese(III)-Iodosylbenzene Catalytic Hydrocarbon Oxidation System. Mechanism and Reaction Chemistry
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The two types of complexes isolated from the reaction of (tetraphenylporphinato)manganese(III) derivatives, XMnIIITPP, with iodosylbenzene - IVTPP(OIPh)>2O, 1, X = Cl- or Br-, and IVTPP>2O, 2, X = N3- - are capable of oxidizing alkane substrates in good yields at room temperature.Several lines of evidence establish the intermediacy of free alkyl radicals in the reactions of 1 and 2 with alkanes.Oxygen exchange with water in both the iodosyl (Mn-O-I) and μ-oxo (Mn-O-Mn) moieties of 1 suggests the formation of oxo manganese porphyrin complexes from these moieties.Hydrogen abstraction from the alkane substrate by an oxo manganese porphyrin intermediate is postulated to be mechanism for reaction of 1 and 2 with alkanes.Observation of a monomeric manganese(IV) porphyrin intermediate by EPR spectroscopy during the reactions of 1 with alkanes is consistent with the formation of a hydroxymanganese(IV) porphyrin complex resulting from substrate hydrogen abstraction by an oxo intermediate.The formation of RX product from oxidation of RH by 1 has been determined to result from ligand-transfer oxidation of free alkyl radicals by the porphyrin complexes in solution.Through competition reactions and time-dependent product formation studies, ligand-transfer oxidation by XMnIIITPP was found to be the major pathway for RX production.Observation of MnIITPP by EPR spectroscopy during the reactions of 1 with alkanes supports this conclusion.Formation of ROH product may result from ligand-transfer oxidation of free radicals or from the collapse of an intermediate caged radical pair.The mechanism of ROH product formation in the caged radical pair is postulated to be an outer-sphere electron-transfer process due to the expected slow rate of inner-sphere ligand transfer for the high-spin d3 hydroxymanganese(IV) porphyrin complex.Thus the ability of the substrate radical to undergo electron-transfer oxidation determines the ratio of radicals that undergo cage escape to give free radicals to radicals that undergo oxidation and subsequent formation of alcohol product in the caged species.Studies with tertiary substrates support these conclusions.
- Smegal, John A.,Hill, Craig L.
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p. 3515 - 3521
(2007/10/02)
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