- The Question of Cyclic Versus Acyclic Ions: The Structure of +. Gas Phase Ions
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The extent of isomerization of acyclic and cyclic gas phase radical cations of composition +. has been investigated by using collisionally activated dissociation spectroscopy.Both electron and charge exchange ionization were employed to form the ions with various internal energies.The +. ions investigated consisted of ionized phenylbutenes, ring-substituted methyl derivatives of allylbenzene and phenylpropene, 1-methyl-isopropenylbenzene, benzylcyclopropane, phenylcyclobutane, tetralin and 1-methylindan.The 1-methylindan and tetralin radical cations are the most stable of the C10H12 isomeric radical ions.The +. formed from acyclic olefins having the double bond in conjugation with the aromatic ring retain the initial structure to a significant extent.However, ions derived from olefins with the double bond out of conjugation with the benzene ring preferentially cyclize to stable five- and six-membered cyclic ions.Ring opening of small-ring cyclic ions, such as ionized benzylcyclopropane and phenylcyclobutane, occurs, followed by ring closure to the tetralin radical cation.
- Dass, Chhabil,Gross, Michael L.
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- Metal-Organic Framework-Confined Single-Site Base-Metal Catalyst for Chemoselective Hydrodeoxygenation of Carbonyls and Alcohols
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Chemoselective deoxygenation of carbonyls and alcohols using hydrogen by heterogeneous base-metal catalysts is crucial for the sustainable production of fine chemicals and biofuels. We report an aluminum metal-organic framework (DUT-5) node support cobalt(II) hydride, which is a highly chemoselective and recyclable heterogeneous catalyst for deoxygenation of a range of aromatic and aliphatic ketones, aldehydes, and primary and secondary alcohols, including biomass-derived substrates under 1 bar H2. The single-site cobalt catalyst (DUT-5-CoH) was easily prepared by postsynthetic metalation of the secondary building units (SBUs) of DUT-5 with CoCl2 followed by the reaction of NaEt3BH. X-ray photoelectron spectroscopy and X-ray absorption near-edge spectroscopy (XANES) indicated the presence of CoII and AlIII centers in DUT-5-CoH and DUT-5-Co after catalysis. The coordination environment of the cobalt center of DUT-5-Co before and after catalysis was established by extended X-ray fine structure spectroscopy (EXAFS) and density functional theory. The kinetic and computational data suggest reversible carbonyl coordination to cobalt preceding the turnover-limiting step, which involves 1,2-insertion of the coordinated carbonyl into the cobalt-hydride bond. The unique coordination environment of the cobalt ion ligated by oxo-nodes within the porous framework and the rate independency on the pressure of H2 allow the deoxygenation reactions chemoselectively under ambient hydrogen pressure.
- Antil, Neha,Kumar, Ajay,Akhtar, Naved,Newar, Rajashree,Begum, Wahida,Manna, Kuntal
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supporting information
p. 9029 - 9039
(2021/06/28)
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- Nickel-catalyzed reductive deoxygenation of diverse C-O bond-bearing functional groups
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We report a catalytic method for the direct deoxygenation of various C-O bond-containing functional groups. Using a Ni(II) pre-catalyst and silane reducing agent, alcohols, epoxides, and ethers are reduced to the corresponding alkane. Unsaturated species including aldehydes and ketones are also deoxygenated via initial formation of an intermediate silylated alcohol. The reaction is chemoselective for C(sp3)-O bonds, leaving amines, anilines, aryl ethers, alkenes, and nitrogen-containing heterocycles untouched. Applications toward catalytic deuteration, benzyl ether deprotection, and the valorization of biomass-derived feedstocks demonstrate some of the practical aspects of this methodology.
- Cook, Adam,MacLean, Haydn,St. Onge, Piers,Newman, Stephen G.
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p. 13337 - 13347
(2021/11/20)
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- Copper-Catalyzed Direct C-H Alkylation of Polyfluoroarenes by Using Hydrocarbons as an Alkylating Source
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Construction of carbon-carbon bonds is one of the most important tools in chemical synthesis. In the previously established cross-coupling reactions, prefunctionalized starting materials were usually employed in the form of aryl or alkyl (pseudo)halides or their metalated derivatives. However, the direct use of arenes and alkanes via a 2-fold oxidative C-H bond activation strategy to access chemoselective C(sp2)-C(sp3) cross-couplings is highly challenging due to the low reactivity of carbon-hydrogen (C-H) bonds and the difficulty in suppressing side reactions such as homocouplings. Herein, we present the new development of a copper-catalyzed cross-dehydrogenative coupling of polyfluoroarenes with alkanes under mild conditions. Relatively weak sp3 C-H bonds at the benzylic or allylic positions, and nonactivated hydrocarbons could be alkylated by the newly developed catalyst system. A moderate-to-high site selectivity was observed among various C-H bonds present in hydrocarbon reactants, including gaseous feedstocks and complex molecules. Mechanistic information was obtained by performing combined experimental and computational studies to reveal that the copper catalyst plays a dual role in activating both alkane sp3 C-H bonds and sp2 polyfluoroarene C-H bonds. It was also suggested that the noncovalent π-πinteraction and weak hydrogen bonds formed in situ between the optimal ligand and arene substrates are key to facilitating the current coupling reactions.
- Xie, Weilong,Heo, Joon,Kim, Dongwook,Chang, Sukbok
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supporting information
p. 7487 - 7496
(2020/08/06)
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- Lewis Base-Promoted Ring-Opening 1,3-Dioxygenation of Unactivated Cyclopropanes Using a Hypervalent Iodine Reagent
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A facile and effective system has been developed for the regio- and chemoselective ring-opening/electrophilic functionalization of cyclopropanes through C?C bond activation by [bis(trifluoroacetoxy)iodo]benzene with the aid of the Lewis basic promoter p-toluenesulfonamide. The p-toluenesulfonamide-promoted system works well for a wide range of cyclopropanes, resulting in the formation of 1,3-diol products in good yields and regioselectivity.
- Gieuw, Matthew H.,Ke, Zhihai,Yeung, Ying-Yeung
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supporting information
p. 3782 - 3786
(2018/03/13)
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- Asymmetric Photocatalytic C-H Functionalization of Toluene and Derivatives
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Reported herein is a visible-light-mediated organocatalytic direct C-H functionalization of toluene derivatives to afford enantioenriched β-benzylated aldehydes from the corresponding enals. The process combines the oxidative power of a chiral excited-state iminium ion and the basic nature of its counteranion to trigger the generation of benzylic radicals by means of a sequential multisite proton-coupled electron transfer mechanism. This study shows that feedstock chemicals generally used as solvents, such as toluene and xylene derivatives, can be used as substrates for making chiral molecules with high enantioselectivity.
- Mazzarella, Daniele,Crisenza, Giacomo E. M.,Melchiorre, Paolo
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supporting information
p. 8439 - 8443
(2018/07/25)
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- Suzuki coupling of potassium cyclopropyl- and alkoxymethyltrifluoroborates with benzyl chlorides
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Efficient Csp3-Csp3 Suzuki couplings have been developed with both potassium cyclopropyl- and alkoxymethyltrifluoroborates. Moderate to good yields have been achieved in the cross-coupling of potassium cyclopropyltrifluoroborate with benzyl chlorides possessing electron-donating or electron-withdrawing substituents. Benzyl chloride was also successfully cross-coupled to potassium alkoxymethyltrifluoroborates derived from primary, secondary, and tertiary alcohols.
- Colombel, Virginie,Rombouts, Frederik,Oehlrich, Daniel,Molander, Gary A.
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scheme or table
p. 2966 - 2970
(2012/06/01)
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- Facile coupling of propargylic, allylic and benzylic alcohols with allylsilane and alkynylsilane, and their deoxygenation with Et3SiH, catalyzed by Bi(OTf)3 in [BMIM][BF4] ionic liquid (IL), with recycling and reuse of the IL
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Allyltrimethylsilane (allyl-TMS) reacts with propargylic alcohols 1a-1d in the presence of 10% Bi(OTf)3 in [BMIM][BF4] solvent to furnish the corresponding 1,5-enynes in respectable isolated yields (87-93%) at room temperature. The utility of Bi(OTf)3 as a superior catalyst was demonstrated in a survey study on coupling of allyl-TMS with 1a employing several metallic triflates (Bi, Ln, Al, Yb) as well as, B(C6F 5)3, Zn(NTf2)2 and Bi(NO 3)3·5H2O. Coupling of cyclopropyl substituted propargylic alcohol 1e with allyl-TMS gave the skeletally intact 1,5-enyne and a ring opened derivative as a mixture. Coupling of propargylic/allylic alcohol 1f with allyl-TMS resulted in allylation at both benzylic (2 isomers) and propargylic positions, as major and minor products respectively. The scope of this methodology for allylation of a series of allylic and benzylic alcohols was explored. Chemoselective reduction of a host of propargylic, propagylic/allylic, bis-allylic, allylic, and benzylic alcohols with Et3SiH was achieved in high yields with short reaction times. The same approach was successfully applied to couple representative propargylic and allylic alcohols with 1-phenyl-2-trimethylsilylacetylene. The recovery and reuse of the ionic liquid (IL) was gauged in a case study with minimal decrease in isolated yields after six cycles.
- Narayana Kumar,Laali, Kenneth K.
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experimental part
p. 7347 - 7355
(2012/09/25)
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- Deoxygenation of benzylic alcohols using chloroboranes
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New boron-based methods for deoxygenating benzylic alcohols via the corresponding alkoxides are reported.
- Yao, Min-Liang,Pippin, Adam B.,Kabalka, George W.
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scheme or table
p. 853 - 855
(2010/03/24)
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- Copper-catalyzed cross-coupling reaction of Grignard reagents with primary-alkyl halides: Remarkable effect of 1-phenylpropyne
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(Chemical Equation Presented) A general get-together: The Cu-catalyzed cross-coupling reaction of primary-alkyl halides with primary-, secondary-, and tertiary-alkyl and phenyl Grignard reagents proceeds efficiently in THF under reflux in the presence of 1-phenylpropyne (see scheme). The reaction is also applicable to alkyl mesylates (OMs) and tosylates (OTs). The reactivities of alkyl-X with a Grignard reagent increase in the order X = Cl F OMs OTs Br.
- Terao, Jun,Todo, Hirohisa,Begum, Shameem Ara,Kuniyasu, Hitoshi,Kambe, Nobuaki
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p. 2086 - 2089
(2008/02/14)
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- Formation of cyclopropanes by homolytic substitution reactions of 3- iodopropyl radicals: Preparative and rate studies
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Reduction of 2-substituted 1,3-diiodopropane derivatives with tin hydride provides substituted cyclopropanes. The reaction occurs through a homolytic substitution of the 3-iodopropyl radical, which has a rate constant of about 5 x 105 s-1 at 80°C.
- Curran, Dennis P.,Gabarda, Ana E.
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p. 3327 - 3336
(2007/10/03)
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- Evidence for the transition from SN to ET mechanism in the reaction of arene radical anion with alkyl halide evoked by the introduction of an electron withdrawing substituent into radical anion
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The interaction of potassium salts of benzonitrile and 1,4-dicyanobenzene radical anions with cyclopropylmethyl bromide provides benzylcyclopropane, in the first case, and 4-alkyl- benzonitriles together with 2-alkyl-1,4-dicyanobenzenes containing both cyclopropylmethyl and it's isomeric 3-butenyl fragment, in the second case. These results provide evidence for the change of reaction mechanism from SN to ET.
- Panteleeva, Elena V.,Vaganova, Tamara A.,Shteingarts, Vitalij D.,Bilkis, Isaak I.
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p. 8465 - 8466
(2007/10/02)
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- RADICAL-ANIONS OF AROMATIC COMPOUNDS. XVII. REACTION OF BENZONITRILE RADICAL-ANION WITH ALKYL HALIDES IN LIQUID AMMONIA
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The main products from the reaction of the potassium salt of the benzonitrile radical-anion with normal alkyl halides (butyl chloride, butyl bromide, butyl iodide, and octyl bromide) in liquid ammonia are the corresponding alkylbenzenes.A small amount of 1-cyano-1-butyl-2,5-cyclohexadiene is also formed in the reactions with butyl iodide and with an excess of butyl bromide.In the reaction of the benzonitrile-4d radical-anion and octyl bromide octyl benzene-4d is formed in an amount corresponding to entry of the alkyl fragment at the ipso position in relation to the cyano group to the extent of not less than 95percent.With cyclopropylmethyl bromide as model it was established that the benzonitrile radical-anion acts as a nucleophile in reaction with alkyl halides.
- Bilkis, I. I.,Vaganova, T. A.,Bobyleva, V. I.,Shteingarts, V. D.
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- STEREOSELECTIVE REDUCTION OF gem-DICHLOROCYCLOPROPANES TO cis-MONOCHLOROCYCLOPROPANES BY LITHIUM ALUMINUM HYDRIDE IN THE PRESENCE OF TITANIUM AND ZIRCONIUM COMPLEXES
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A versatile stereoselective method in presented for the synthesis of cis-monochlorocyclopropanes by the reduction of dehalogenated alkyl- and aryl-gem-dichlorocyclopropanes in the presence of catalytic quantities of titanium and zirconium complexes.
- Dzhemilev, U. M.,Gaisin, R. L.,Turchin, A. A.,Tolstikov, G. A.
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p. 1845 - 1848
(2007/10/02)
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- Photochemistry of alkyl halides. 12. Bromides vs Iodides
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Conditions have been developed for optimizing ionic photobehavior material balances from alkyl bromides. Hydroxide ion as an efficient for the byproduct HBr while giving minimal competing photoreduction via electron transfer to the alkyl bomide. The photobehavior of bromides 1, 11, 25, and 40 has examined and with that of the corresponding iodides 2, 12, 26, 41 under conditions. In each case, the bromide higher yields of products derived from out of cage radical intermidiates than the corresponding iodide. However, with the 2-norbornyl bromides 11 and iodides 12 showed that, of products not formed from the out of cage 2-norbornyl radical 13, the bromides 11 gave a higher percentage of products from the ionic intermediates 15 and 16 than did the iodides. Thus, electron transfer within the radical pair 14 is apparently more rapid for bromides than iodides, as expected on the of the relative electronegativities of bromine iodine. It is that the substantially higher yields of out of radical products from alkyl bromides may be due in to formation of the radical pair with greater excess energy, which results in more rapid escape from the cage. The epimeric 2-norbornyl bromides 11x and 11n underwent no detectable interconversion and afforded somewhat different product ratios. The more hindered epimer 11n underwent conversion to products at a slower than 11x. By contrast, 12x and 12n underwent substantial interconversion via out of transfer of an iodine atom from iodide 12 to radical 13. Epimerization was significantly attenuated in the more viscous solvent tert-butyl alcohol.
- Kopp, Paul J.,Adkins, Rick L.
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p. 2709 - 2717
(2007/10/02)
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- EFFICIENT METHOD FOR THE SYNTHESIS OF MONOHALOCYCLOPROPANES BY REDUCTION OF GEM-DIHALOCYCLOPROPANES BY REDUCTION OF GEM-DIHALOCYCLOPROPANES WITH i-Bu2AlH IN THE PRESENCE OF Ti AND Zr COMPLEXES
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We have investigated the reductive dehalogenation reaction of alkyl and aryl substituted gem-dihalocyclopropanes with diisobutyl aluminum hydride in the presence of catalytic amounts of titanium and zirconium complexes.As a result we propose a general method for the synthesis of substituted monohalocyclopropanes and cyclopropanes of various structures.We have also studied the stereochemistry of the reduction.
- Dzhemilev, U. M.,Gaisin, R. L.,Turchin, A. A.,Khalikova, N. R.,Baikova, I. P.,Tolstikov, G. A.
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p. 967 - 974
(2007/10/02)
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- METHYLENATION OF CARBONYL COMPOUNDS WITH METHYLENEDIMAGNESIUM IODIDE IN THE PRESENCE OF Et2AlCl
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A method has been developed for the methylenation of carbonyl compounds with methylenedimagnesium iodide in the presence of Et2AlCl in 35-70percent yield.In the presence of catalytic amounts of Ti and Pd complexes the yield of methylenation products is increased by 15-20percent.
- Dzhemilev, U. M.,Ibragimov, A. G.,Morozov, A. B.,Muslukhov, R. R.,Tolstikov, G. A.
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p. 2350 - 2352
(2007/10/02)
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- REACTIONS OF DIAZOALKANES WITH UNSATURATED COMPOUNDS. 6. CATALYTIC CYCLOPROPANATION OF UNSATURATED HYDROCARBONS AND THEIR DERIVATIVES WITH DIAZOMETHANE
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A systematic study has been conducted of the catalytic reaction of diazomethane with cyclic and polycyclic unsaturated hydrocarbons, conjugated dienes, as well as with a series of functionalized unsaturated conpounds.The feasibility of using transition metal, nontransition metal, and rare earth metal compounds of, for example, Co, Ni, Zr, Rh, and Dy, has been demonstrated for the first time.It has also been established that Pd(acac)2 has very high activity as a catalyst for the cyclopropanation of terminal and endocyclic double bonds by diazomethane, and that its activity is reduced upon the introduction of n-donor ligands or in the presence of strong polar solvents.
- Dzhemilev, U. M.,Dokichev, V. A.,Sultanov, S. Z.,Khusnutdinov, R. I.,Tomilov, Yu. V.,et al.
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p. 1707 - 1714
(2007/10/02)
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- BENZYL- and 2- AND 4-NITROBENZYLCYCLOPROPANES AND THEIR REACTION WITH ORGANIC ACIDS
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The nitration of benzylcyclopropane and its transformations in organic acids were studied.Under the conditions of electrophilic nitration the small ring is preserved, while the ratio of the o- and p-nitrophenyl derivatives amounts to 1.1:1.The reaction of benzylcyclopropane with formic and acetic acids takes place with the addition of the fragments of the acids at the 1,2-bond of the three-carbon ring; o- and p-nitrobenzylcyclopropanes do not react with formic and acetic acids, with trifluoroacetic acid they form trifluoroacetates, and in the case of the ortho-substituted isomer nucleophilic assistance from the nitro group is observed.
- Fedotov, A. N.,Trofimova, E. V.,Mochalov, S. S.,Shabarov, Yu. S.
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p. 1272 - 1275
(2007/10/02)
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- β-STANNYLPROPIONALDEHYDE. A VERSATILE CYCLOPROPANE BUILDING-BLOCK
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Various functional group-substituted cyclopropanes were prepared in good yield starting from β-tributylstannylpropionaldehyde via homoallyl-stannanes or γ-hydroxypropylstannanes.
- Ueno, Yoshio,Ohta, Mitsuaki,Okawara, Makoto
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p. 2577 - 2580
(2007/10/02)
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