- Ethylenebis(N-methylimidazolium) ditribromide (EBMIDTB): An efficient reagent for the monobromination of 1,3-diketones and β-ketoesters
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Ethylenebis(N-methylimidazolium) ditribromide, a stable crystalline solid, is easily prepared by reaction of the corresponding dibromide salt with bromine in n-hexane. 1,3-Diketones and β-ketoesters can be brominated chemoselectively to the corresponding α-monobrominated products by using this reagent at 0-5°C. Under the same reaction conditions, diethyl malonate, ethyl cyanoacetate, and malonitrile were monobrominated at moderate yield.
- Hosseinzadeh, Rahman,Tajbakhsh, Mahmood,Mohadjerani, Maryam,Lasemi, Zahra
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experimental part
p. 57 - 60
(2010/03/30)
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- One-pot synthesis of 2-(2-alkoxy-5-amino-4-cyano-2-methylfuran-3(2H)- ylidene)malononitriles
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A new preparative method was developed for the synthesis of 2-(2-alkoxy-5-amino-4-cyano-2-methyl-3(2H)-ylidene)malononitriles in a single stage from readily obtainable reagents.
- Bardasov,Kayukova,Kayukov,Ershov,Belikov,Nasakin
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experimental part
p. 1035 - 1038
(2010/04/06)
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- Chemical reactivity of 3-hydrazino-5,6-diphenyl-1,2,4-triazine towards π-acceptors activated carbonitriles
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Behaviour of 3-hydrazino-5,6-diphenyl-1,2,4-triazine 1 as electron donor towards different electron acceptors activated carbonitriles has been investigated and a novel fused heterocyclic system and 2,3-disubstituted 1,2,4-triazines have been obtained. Compound 1 reacts with 1,2-dicyanobenzene as π-acceptor in DMF to form benzencarboximidamide 16, while reaction of 1 with a-bromomalononitrile 17 in boiling DMF affords compound 18. On the other hand, compound 1 reacts with tetracyanoethane 23 in DMF to yield compound 24. The route of reaction in DMF indicates that charge-transfer complexation is the key intermediate to obtain new heterocyclic systems. Structures of the products are established by MS, IR, UV-Vis, CHN and 1H NMR spectral data.
- Abdel-Rahman,Abdel-Monem
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p. 838 - 846
(2008/09/18)
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- Tetrameric DABCO-bromine: An efficient and versatile reagent for bromination of various organic compounds
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Tetrameric DABCO-bromine is a powerful brominating agent but shows reasonable selectivity with certain substrates. The selective bromination for activated aromatic compounds and alkenes is reported. Synthesis of α-bromo ketones and nitriles has also been achieved by using this reagent and the results are also reported. All products reported were obtained in good to excellent yields.
- Heravi, Majid M.,Derikvand, Fatemeh,Ghassemzadeh, Mitra
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p. 125 - 128
(2007/10/03)
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- Microwave-assisted synthesis of some BI- and tricyclic pyrimidine derivatives
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Pyrimidine derivatives 4a-4c was prepared by a Biginelli cyclocondensation of β-ketoesters, aryl aldehydes, and thiourea derivatives under microwave irradiation. A simple and fast synthesis of bicyclic pyrimidine derivatives 6a-6c was performed by microwave-assisted reaction of 4a-4c with bromomalononitrile (5). Reaction of bicyclic pyrimidines 6a-6c with HCO2H and HONH3Cl under microwave irradiation gave tricyclic pyrimidines 7a-7c and 8a-8c respectively.
- Foroughifar,Mobinikhaledi,Jirandehi, H. Fathinejad,Memar
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p. 1269 - 1276
(2007/10/03)
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- Photoinduced Nitrene, Carbene, and Atomic Oxygen Transfer Reactions Starting from the Corresponding Pyridinium N-, C-, and O-Ylides
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Ultraviolet irradiation of the pyridinium ylides 1, 2, and 3 led to fragmentation of the exocyclic polar bonds, as well as to skeletal rearrangements.The photoinduced fragmentation processes gave the corresponding pyridines and highly reactive intermediates, i. e. ethoxycarbonylnitrene, dicyanocarbene and atomic oxygen (oxene), respectively.Trapping of the reactive intermediates by alkanes and alkenes permitted the determination of their spin multiplicity.Ethoxycarbonylnitrene was in its triplet ground state at the moment of its formation.Dicyanocarbene occurred as a mixture of singlet and triplet, as determined by dilution experiments with variable amounts of alkenes.As to atomic oxygen, all collected data point to its formation in solution in its triplet ground state.
- Strub, Henri,Strehler, Christiane,Streith, Jacques
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p. 355 - 364
(2007/10/02)
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- Cyanocarbon Acids: Direct Evidence That Their Ionization Is Not an Encounter-Controlled Process and Rationalization of the Unusual Solvent Isotope Effects
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The rate of exchange of the acidic hydrogen of tert-butylmalononitrile was examined by using as a tracer, and the process was found not to be inhibited by hydronium ions in dilute aqueous hydrochloric acid solutions.This rules out the Swain-Grunwald mechanism for this reaction under these conditions.The bromination of malonitrile was investigated under conditions where reprotonation of the dicyanomethyl carbanion and its reaction with bromine occur at comparable rates, and the bromination reaction was found to have a specific rate twice that for reprotonation.Reprotonation therefore cannot be a diffusion-controlled process, and malonitrile is not a "normal" acid.The unusually large solvent kinetic isotope effects found for these cyanocarbon acid ionization reactions are explained by postulating that the transferring hydrogen and its positive charge are becoming associated with a solvent cluster rather than with a single water molecule.The thermodynamic acidity constant of malonitrile was determined to be 11.41 in aqueous solution at 25 deg C.
- Hojatti, M.,Kresge, A. J.,Wang, W.-H.
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p. 4023 - 4028
(2007/10/02)
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