- Cerium-Catalyzed C-H Functionalizations of Alkanes Utilizing Alcohols as Hydrogen Atom Transfer Agents
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Modern photoredox catalysis has traditionally relied upon metal-to-ligand charge-transfer (MLCT) excitation of metal polypyridyl complexes for the utilization of light energy for the activation of organic substrates. Here, we demonstrate the catalytic application of ligand-to-metal charge-transfer (LMCT) excitation of cerium alkoxide complexes for the facile activation of alkanes utilizing abundant and inexpensive cerium trichloride as the catalyst. As demonstrated by cerium-catalyzed C-H amination and the alkylation of hydrocarbons, this reaction manifold has enabled the facile use of abundant alcohols as practical and selective hydrogen atom transfer (HAT) agents via the direct access of energetically challenging alkoxy radicals. Furthermore, the LMCT excitation event has been investigated through a series of spectroscopic experiments, revealing a rapid bond homolysis process and an effective production of alkoxy radicals, collectively ruling out the LMCT/homolysis event as the rate-determining step of this C-H functionalization.
- An, Qing,Chen, Yuegang,Liu, Weimin,Pan, Hui,Wang, Xin,Wang, Ziyu,Zhang, Kaining,Zuo, Zhiwei
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p. 6216 - 6226
(2020/04/27)
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- Carbon Dioxide-Mediated C(sp2)-H Arylation of Primary and Secondary Benzylamines
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C-C bond formation by transition metal-catalyzed C-H activation has become an important strategy to fabricate new bonds in a rapid fashion. Despite the pharmacological importance of ortho-arylbenzylamines, however, effective ortho-C-C bond formation of free primary and secondary benzylamines using PdII remains an outstanding challenge. Presented herein is a new strategy for constructing ortho-arylated primary and secondary benzylamines mediated by carbon dioxide (CO2). The use of CO2 with Pd is critical to allowing this transformation to proceed under relatively mild conditions, and mechanistic studies indicate that it (CO2) is directly involved in the rate-determining step. Furthermore, the milder temperatures furnish free amine products that can be directly used or elaborated without the need for deprotection. In cases where diarylation is possible, an interesting chelate effect is shown to facilitate selective monoarylation.
- Kapoor, Mohit,Chand-Thakuri, Pratibha,Young, Michael C.
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supporting information
p. 7980 - 7989
(2019/05/22)
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- Acid Is Key to the Radical-Trapping Antioxidant Activity of Nitroxides
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Persistent dialkylnitroxides (e.g., 2,2,6,6-tetramethylpiperidin-1-oxyl, TEMPO) play a central role in the activity of hindered amine light stabilizers (HALS)-additives that inhibit the (photo)oxidative degradation of consumer and industrial products. The accepted mechanism of HALS comprises a catalytic cycle involving the rapid combination of a nitroxide with an alkyl radical to yield an alkoxyamine that subsequently reacts with a peroxyl radical to eventually re-form the nitroxide. Herein, we offer evidence in favor of an alternative reaction mechanism involving the acid-catalyzed reaction of a nitroxide with a peroxyl radical to yield an oxoammonium ion followed by electron transfer from an alkyl radical to the oxoammonium ion to re-form the nitroxide. In preliminary work, we showed that TEMPO reacts with peroxyl radicals at diffusion-controlled rates in the presence of acids. Now, we show that TEMPO can be regenerated from its oxoammonium ion by reaction with alkyl radicals. We have determined that this reaction, which has been proposed to be a key step in TEMPO-catalyzed synthetic transformations, occurs with k ~ 1-3 × 1010 M-1 s-1, thereby enabling it to compete with O2 for alkyl radicals. The addition of weak acids facilitates this reaction, whereas the addition of strong acids slows it by enabling back electron transfer. The chemistry is shown to occur in hydrocarbon autoxidations at elevated temperatures without added acid due to the in situ formation of carboxylic acids, accounting for the long-known catalytic radical-trapping antioxidant activity of TEMPO that prompted the development of HALS.
- Haidasz, Evan A.,Meng, Derek,Amorati, Riccardo,Baschieri, Andrea,Ingold, Keith U.,Valgimigli, Luca,Pratt, Derek A.
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supporting information
p. 5290 - 5298
(2016/05/19)
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- Self-propagated Lossen rearrangement induced by a catalytic amount of activating agents under mild conditions
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A mild self-propagated Lossen rearrangement induced by a catalytic amount of activating agents in medium to high polar organic solvents has been developed. The rearrangement of aromatic and aliphatic hydroxamic acids in the presence of a catalytic amount (0.01 equiv) of acetic anhydride and an equimolar amount of base such as well-dried potassium carbonate afforded the corresponding amines in high yields. This alternative to traditional Lossen rearrangement provides a simple and mild method for the synthesis of amines from free hydroxamic acids.
- Hoshino, Yujiro,Shimbo, Yuki,Ohtsuka, Naoya,Honda, Kiyoshi
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supporting information
p. 710 - 712
(2015/01/30)
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- PRODUCTION METHOD FOR COMPOUND COMPRISING AMINO GROUP AND/OR HYDROXYL GROUP
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Disclosed is a method for producing a compound having an amino group and/or a hydroxyl group from a substrate compound having an atomic group containing CO or CS by eliminating said atomic group. The substrate compound having an atomic group containing CO or CS (for example, an amide, a carbamate, or the like) is allowed to react with a compound expressed by formula (I) below, at a temperature of 120°C or lower, preferably in the presence of an ammonium salt, to eliminate said atomic group containing CO or CS. In formula (I) A may not be present, and in a case where A is present, A represents an alkyl group having 1 to 6 carbon atoms. ????????H2N-A-NH2?????(I)
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Paragraph 0040; 0043
(2015/01/18)
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- Selective and potent urea inhibitors of cryptosporidium parvum inosine 5′-monophosphate dehydrogenase
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Cryptosporidium parvum and related species are zoonotic intracellular parasites of the intestine. Cryptosporidium is a leading cause of diarrhea in small children around the world. Infection can cause severe pathology in children and immunocompromised patients. This waterborne parasite is resistant to common methods of water treatment and therefore a prominent threat to drinking and recreation water even in countries with strong water safety systems. The drugs currently used to combat these organisms are ineffective. Genomic analysis revealed that the parasite relies solely on inosine-5′-monophosphate dehydrogenase (IMPDH) for the biosynthesis of guanine nucleotides. Herein, we report a selective urea-based inhibitor of C. parvum IMPDH (CpIMPDH) identified by high-throughput screening. We performed a SAR study of these inhibitors with some analogues exhibiting high potency (IC50 1000-fold versus human IMPDH type 2 and good stability in mouse liver microsomes. A subset of inhibitors also displayed potent antiparasitic activity in a Toxoplasma gondii model.
- Gorla, Suresh Kumar,Kavitha, Mandapati,Zhang, Minjia,Liu, Xiaoping,Sharling, Lisa,Gollapalli, Deviprasad R.,Striepen, Boris,Hedstrom, Lizbeth,Cuny, Gregory D.
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p. 7759 - 7771
(2012/11/06)
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- Directed ortho -metalation-cross-coupling strategies. One-pot Suzuki reaction to biaryl and heterobiaryl sulfonamides
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A general synthesis of stable ortho-boropinacolato aryl and heteroaryl sulfonamides by directed ortho-metalation (DoM) and either MeOBPin or i-PrOBpin electrophile quench, 3 → 4, is described. A one-pot metalation-Suzuki cross-coupling procedure for the synthesis of biaryls and heterobiaryls, 3 → 5, and a complementary DoM-Ir-catalyzed boronation sequence (Scheme 6) are delineated.
- Schneider, Cedric,Broda, Ellen,Snieckus, Victor
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supporting information; experimental part
p. 3588 - 3591
(2011/10/03)
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- Rapid Ti(Oi-Pr)4 facilitated synthesis of α,α,α-trisubstituted primary amines by the addition of Grignard reagents to nitriles under microwave heating conditions
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A series of carbinamines (α,α,α-trisubstituted amines) have been prepared in a simple and efficient one-pot procedure by the addition of Grignard reagents to a series of aliphatic, aromatic and heteroaromatic nitriles. The resulting magnesium imines are subsequently converted to the desired amine after treatment with Ti(Oi-Pr)4 and additional microwave heating. Key to this procedure is the use of microwave heating for both steps of the reaction protocol, which significantly improves both reaction yields and reduces reaction times. In general, the Grignard addition reaction is complete within 5-10 min at 100 °C followed by conversion with Ti(Oi-Pr)4 and additional microwave heating to give the target amines in good yields.
- Wang, Ruifang,Gregg, Brian T.,Zhang, Wei,Golden, Kathryn C.,Quinn, John F.,Cui, Peng,Tymoshenko, Dmytro O.
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experimental part
p. 7070 - 7073
(2010/03/01)
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- Directed Ortho metalation-cross coupling strategies. N-cumyl arylsulfonamides. Facile deprotection and expedient route to 7- and 4,7-substituted saccharins
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(Chemical Equation Presented) By using the powerful N-cumylsulfonamide directed metalation group (DMG), a series of 2-substituted derivatives were prepared according to the directed ortho metalation (DoM) tactic (Table 1). Mild conditions for N-decumylation and other simple transformations of the products have been achieved (Scheme 2). The 3-silyloxy sultam 12 undergoes further DoM to give formyl, thiomethyl, iodo, and amide derivatives 13a-g of potential value for saccharin synthesis (Table 2). An effective route to target 7-aryl saccharins via Suzuki cross coupling (Table 3) followed by further metalation-carbamoylation and cyclization (Table 5) is described. 4,7-Disubstituted saccharins have been obtained by similar sequences (Scheme 3). Mild TFA-mediated N-decumylation furnishes substituted primary arylsulfonamides (Table 4).
- Blanchet, Jerome,Macklin, Todd,Ang, Patrick,Metallinos, Costa,Snieckus, Victor
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p. 3199 - 3206
(2008/02/04)
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- Evidence for significant through-space and through-bond electronic coupling in the 1,4-diphenylcyclohexane-1,4-diyl radical cation gained by absorption spectroscopy and DFT calculations
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Photoinduced single-electron-transfer promoted oxidation of 2,5-diphenyl-l,5-hexadiene by using N-methylquinolinium tetrafluoroborate/ biphenyl co-sensitization takes place with the formation of an intense electronic absorption band at 476 nm, which is attributed to the 1,4-diphenylcyclohexane-1,4-diyl radical cation. The absorption maximum (λob) of this transient occurs at a longer wavelength than is expected for either the cumyl radical or the cumyl cation components. Substitution at the para positions of the phenyl groups in this radical cation by CH3O, CH3, F, Cl, and Br leads to an increasingly larger redshift of λob. A comparison of the ρ value, which was obtained from a Hammett plot of the electronic transition energies of the radical cations versus σ+, with that for the cumyl cation shows that the substituent effects on the transition energies for the 1,4-diarylcyclohexane-1,4-diyl radical cations are approximately one half of the substituent effects on the transition energies of the cumyl cation. The observed substitu_ent-induced redshifts of λob and the reduced sensitivity of λob to substituent changes are in accordance with the proposal that significant through-space and -bond electronic interactions exist between the cumyl radical and the cumyl cation moieties of the 1,4-diphenylcyclohexane-1,4-diyl radical cation. This proposal gains strong support from the results of density functional theory (DFT) calculations. Moreover, the results of time-dependent DFT calculations indicate that the absorption band at 476 nm for the 1,4-diphenylcyclohexane-1,4-diyl radical cation corresponds to a SOMO-3-SOMO transition.
- Ikeda, Hiroshi,Hoshi, Yosuke,Namai, Hayato,Tanaka, Futoshi,Goodman, Joshua L.,Mizuno, Kazuhiko
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p. 9207 - 9215
(2008/12/21)
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- One-pot synthesis of primary tert-alkylamines by the addition of organometallic reagents to nitriles mediated by Ti(Oi-Pr)4
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A number of primary tert-alkylamines (18 examples, 25-72% yields) have been prepared according to a simple one-pot procedure by the addition of organometallic reagents such as Grignard reagents and organolithium compounds to nitriles in the presence of Ti(Oi-Pr)4. Georg Thieme Verlag Stuttgart.
- Tomashenko, Olesya,Sokolov, Viktor,Tomashevskiy, Alexander,De Meijere, Armin
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p. 652 - 654
(2007/10/03)
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- Efficient one-pot formation of 4-N-substituted 2,4-dihydro-3H-1,2,4-triazolin-3-ones from primary amines using N′-(ethoxymethylene)hydrazinecarboxylic acid methyl ester
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(E)-N′-(Ethoxymethylene)hydrazinecarboxylic acid methyl ester was synthesized in one step in good yield. This reagent was successfully applied to the one-pot synthesis of 4-substituted 2,4-dihydro-3H-1,2,4-triazolin-3-ones from readily available primary alkyl and aryl amines. This reaction process is relatively mild and easy to carry out. It is especially useful for the formation of sterically hindered triazolinones, which are otherwise difficult to obtain via existing literature procedures. A possible mechanistic pathway for the transformation is outlined.
- Shao, Ning,Wang, Cheng,Huang, Xianhai,Xiao, Dong,Palani, Anandan,Aslanian, Robert,Shih, Neng-Yang
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p. 6743 - 6746
(2007/10/03)
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- Behaviour of N-pyridylbenzamides versus benzanilides in the ortho-directed lithiation of masked aromatic carboxylic acids
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The reaction of N-pyridylbenzamides 1-3 with n-butyllithium or sec-butyllithium has been examined. The perfect selectivity that has been observed until now in the lithiation of anilides, a reaction used for ortho-functionalisation of masked aromatic carboxylic acids, has been broken; our results indicate that the pyridine ring at the position ortho to the directed metallation group is more susceptible to lithiation than the homoaromatic ring itself. This was proved in an intermolecular comparative study of benz-, picolin- and isonicotinanilides 14-16, and N-cumylbenzamide (17). Wiley-VCH Verlag GmbH & Co. KGaA, 69451 Weinheim, Germany, 2004.
- Jozwiak, Andrzej,Brzezinski, Jacek Z.,Plotka, Mieczyslaw W.,Szczesniak, Aleksandra K.,Malinowski, Zbigniew,Epsztajn, Jan
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p. 3254 - 3261
(2007/10/03)
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- Thermolysis of free-radical initiators: tert-butylazocumene and its 1,3- and 1,4-bisazo and 1,3,5-trisazo analogues
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Four tert-butylazocumenes (4-7) were prepared from the corresponding cyanobenzenes, and their nitrogen evolution kinetics and products were analyzed. In combination with TEMPO, the simplest compound, tert-butylazocumene (4), shows promise as a "one-radical" initiator of styrene polymerization. The ABNO-trapped cumyl radical 29 is a particularly stable trialkylhydroxylamine, whose thermolysis half-life is 2.1 h at 150 °C. Taking advantage of this stability, we trapped the cumyl radical centers from 7 to afford tris adduct 32a. While the behavior of the meta bisazoalkane 6 can be mostly predicted from that of 4, the para isomer 5 exhibits both unusual products and kinetics, attributed to the formation of quinodimethane 33 via azo-containing radical 34. In fact, flash vacuum pyrolysis of 5 allowed observation of the 1H and 13C NMR spectra of 33, whose persistence even at ambient temperature showed that this quinodimethane is far more stable than the parent 36. Finally, evidence is presented that 7 is an initiator of star polymerization.
- Engel,Pan,Ying,Alemany
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p. 3706 - 3715
(2007/10/03)
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- The electrochemical reduction of α-nitrocumene in a protic and basic medium on large surface area (porous) electrodes: Electronation-protonation or electrocatalytic hydrogenation?
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The electrochemical reduction of α-nitrocumene (1) has been investigated under controlled potential, at a mercury pool cathode and at Raney metal (Raney nickel, Raney cobalt and Devarda copper) and fractal nickel electrodes in basic aqueous ethanol. A comparison of the product distribution from the reduction at Hg (electronation-protonation (EP) mechanism) and that from the reduction at Raney metals and fractal nickel has shown that both the electrocatalytic hydrogenation (ECH) and EP mechanisms can be involved at large surface area (porous) transition metal electrodes in a basic protic medium. Cyclic voltammetry was used to determine the reduction potential of 1 at Hg and at bright polycrystalline nickel, cobalt, and copper cathodes in the same medium.
- Chan-Shing, Elisa Soazara,Boucher, Denys,Lessard, Jean
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p. 687 - 694
(2007/10/03)
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- N-cumyl benzamide, sulfonamide, and aryl O-carbamate directed metalation groups. Mild hydrolytic lability for facile manipulation of directed ortho metalation derived aromatics
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(Matrix Presented) N-Cumyl benzamide (2), sulfonamide (8), and O-carbamate (11) compounds undergo directed ortho metalation under standard conditions to give, after quench with a variety of electrophiles, the substituted products 3, 9, and 12, respectively. Regiospecific and convenient approaches to phthalimides (7), 1,2-benzisothiazole 1,1-dioxides (10b), and ortho-substituted phenols (13a) and salicylamides (13b) are thereby established The mild deprotection protocol for these new cumyl directed metalation groups (DMGs) suggests that they will supersede previous corresponding groups for synthetic anionic aromatic chemistry.
- Metallinos, Costa,Nerdinger, Sven,Snieckus, Victor
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p. 1183 - 1186
(2008/02/09)
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- Syntheses and reactions of 1-amino-2,2-dialkylcyclopropane-1- carbonitriles and -carboxamides - Potential precursors of ACC derivatives
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The direct cyclization of 2-amino-4-chloro,3,3-dimethylbutanenitrile with potassium tert-butoxide in THF afforded 1-amino-2,2- dimethylcyclopropane-1-carbonitrile and a dimerization product. Various new cis- and trans-1-(tert-butylamino)-2-benzyl-2-methylcyclopropane- carbonitriles and the corresponding cyclopropanecarboxamides have been synthesized, with focus on the isolation of the pure stereoisomeric cyclopropanecarboxamides. The relative configuration of the stereoisomers was established by X-ray crystallographic analysis of one of the model compounds. A new route to the latter functionalized cyclopropanes was developed by reaction of 1-methoxycyclopropylamines with potassium cyanide. Some remarkable rearrangements of 1-aminocyclopropane-1-carbonitriles into azetidine and oxazine derivatives via Favorskil-derived intermediates are reported. Various aspects of the chemistry of geminally functionalized cyclopropanes are discussed.
- Aelterman, Wim,Tehrani, Kourosch Abbaspour,Coppens, Wim,Huybrechts, Tom,De Kimpe, Norbert,Tourwe, Dirk,Declercq, Jean-Paul
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p. 239 - 250
(2007/10/03)
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- Sulfenamide accelerators and rubber compositions containing the same
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Novel mono- and bis-benzothiazole sulfenamide compounds based on primary amines are provided which may be employed as rubber vulcanization accelerators having excellent scorch safety. Vulcanizable rubber compositions containing rubber, sulfur and the novel benzothiazole sulfenamide compounds are also provided.
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- Organocerium reactions of benzamides and thiobenzamides: A direct synthesis of tertiary carbinamines
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A simple and efficient process has been developed for the direct conversion of benzamides and thiobenzamides into tertiary carbinamines. A synthesis of benzonitriles from simple benzamides and a thiobenzamide is also described.
- Calderwood, David J.,Davies, Roy V.,Rafferty, Paul,Twigger, Helen L.,Whelan, Helen M.
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p. 1241 - 1244
(2007/10/03)
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- Electron-Transfer Substitution Reactions: Facilitation by the Cyano Group
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It is now clear that a cyano group facilitates electron-transfer substitution reactions.Of particular interest is the demonstration that electron-transfer chain substitution at a saturated carbon atom has been achieved in the absence of a nitro group.
- Kornblum, Nathan,Fifolt, Michael J.
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p. 1311 - 1322
(2007/10/02)
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- Screw Sense Selective Polymerization of Achiral Isocyanides Catalysed by Optically Active Nickel(II) Complexes
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Poly(isocyanides), (RN=Cn, can be prepared from isocyanides, , by the catalytic action of nickel(II) compounds.The main chain of these polymers is a rigid helix.This helical conformation results from a restricted rotation around the single bonds that connect the main-chain carbon atoms.Polymerization of achiral isocyanides generally gives a racemic mixture of left- and right-handed helices, whereas polymerization of optically active isocyanides results in helices with an excess of one screw sense.We describe a procedure for obtaining poly(isocyanides) with predominantly one screw sense, starting from an achiral monomer.A catalyst is prepared by adding an optically active amine to a tetrakis(isocyanide)nickel(II) perchlorate complex.Polymerization of various achiral isocyanides with this catalist yields optically active polymers with an enantiomeric excess up to 83percent.
- Kamer, Paul C. J.,Nolte, Roeland J. M.,Drenth, Wiendelt
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p. 6818 - 6825
(2007/10/02)
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- Synthesis and Herbicidal Activities of 1,2-Benzisoxazole-3-acetamide Derivatives
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Many 1,2-benzisoxazole-3-acetamides were synthesized and their herbicidal activities in the paddy field were studied.Of the compounds tested, N-α,α-dimethylbenzyl-2-bromo-(1,2-benzisoxazol-3-yl)acetamide 10a was the most effective.Details of the synthesis and the results of herbicidal evaluations are given.
- Sato, Kazuo,Honma, Toyokuni,Sugai, Soji
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p. 3563 - 3568
(2007/10/02)
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- Thiadiaziridine 1,1-Dioxides: Synthesis and Chemistry
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The synthesis and chemical reactions of a series of thiadiaziridine 1,1-dioxides (2) are described.The thermal stability is highly dependent on the R group and in one case (R = tert-octyl) is postulated that the thermolysis initially produces a diradical intermediate which can be trapped or further fragments to give a nitrene.A temperature-dependent NMR study on the coalescence of the diastereotopic α-methyl protons of 2b gives a ΔG = 20 kcal*mol-1.
- Timberlake, Jack W.,Alender, Jeff,Garner, Archie W.,Hodges, Melvin L.,Oezmeral, Cenan,et al.
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p. 2082 - 2089
(2007/10/02)
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- Decomposition of Azocumene on Silica Surfaces
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The decomposition of azocumene on silica surfaces in the absence of solvent is slower than in toluene solution and has a much lower radical efficiency.Radicals that escape geminate reaction can be trapped by adsorbed bisdiphenylenephenylallyl.The ratio of cumene to α,α-dicumyl is about five times that in toluene.Aromatized α-ortho and α-para cumyl dimers, found only in the reactions on silica, are formed in low yield.These products (10 and 11) are formed via the quinoidal α-ortho and α-para dimers, which have been reported as transient products in toluene.The aromatized dimers (10 and 11) are exclusively geminate recombination products, presumably because they are formed only if the site at which the azocumene decomposes is also a catalytic site for the aromatization of the quinoidal dimers.The rates and product ratios depend to some extent on the purity and degree of hydroxylation of the silica.They also depend on the fraction of a monolayer occupied by the azocumene.At low monolayer coverages the azocumene is preferentially adsorbed on sites that give lower rates, higher cumene to α,α-dicumyl ratios, and higher yields of the aromatized dimers 10 and 11.The silicas were characterized by their acidities, Rf values, catalytic properties, and the electron paramagnetic resonance spectra of adsorbed radicals.
- Leffler, J. E.,Zupancic, J. J.
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p. 259 - 267
(2007/10/02)
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