- Absolute Rate Constants for Bromine Abstraction from N-Bromoimides and Br2 by Alkyl Radicals
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Imidyl radicals react with cyclopropanes solely via hydrogen abstraction.In the case of methylcyclopropane, the major product (cyclopropylcarbinyl bromide) is derived from abstraction of hydrogen from the methyl group.The resultant cyclopropylcarbinyl radical is partioned between two pathways: (1) abstraction of Br from N-bromoimide and (2) rearrangement to the allylcarbinyl radical (eventually yielding 4-bromo-1-butene).Since the absolute rate of the rearrangement is known, an absolute rate constant for the abstraction of Br from N-bromoimides by alkyl radicals can be derived (CH2Cl2 solvent, 15 deg C), k ca. (1.3-1.6)1xE10 M-1s-1.Reactions carried out in the presence of Br2 provide a third pathway for scavenging of the cyclopropylcarbinyl radical, providing kBr2=2.2x1E10 M-1s-1.Thus, trapping of primary R. by either N-bromoimides or Br2 occurs at rates that are diffusion-controlled.
- Tanko, James M.,Skell, Philip S.,Seshadri, Sri
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- Facile Preparation of Λ-Shaped Building Blocks: Hünlich Base Derivatization
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Hünlich's base modification has resulted in introducing a series of versatile Λ-shaped building blocks presented in this work. The methods are optimized to provide convenient approaches in the quicker production of these new building blocks in low-cost and low-risk.
- Kazem-Rostami, Masoud
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- Ionic Bromination of Ethane and Other Alkanes (Cycloalkanes) with Bromine Catalyzed by the Polyhalomethane*2AlBr3 Aprotic Organic Superacids under Mild Conditions
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The polyhalomethane*2AlBr3 aprotic organic superacids were shown to effectively catalyze low-temperature ionic bromination of (cyclo)alkanes.Ethane readily reacts with Br2 at 55-65 deg C, affording mainly 1,2-dibromoethane.Propane, butane, and C5-C6 cycloalkanes react at -40 - -20 deg C, resulting in monobromides with high yields and good selectivity.
- Akhrem, Irena S.,Orlinkov, Alexander V.,Afanas'eva, Lyudmila V.,Mysov, Evgenii I.,Vol'pin, Mark E.
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- Direct and Regioselective Transformation of α-Chloro Carbonyl Compounds into Alkenes and Deuterioalkenes
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The successive treatment ethyl chloroacetate or chloroacetyl chloride with Grignard reagents and lithium powder leads to symmetrical terminal olefins in a regioselective manner.The best results are obtained with acid chlorides.The influence of the temperature and the reaction time on overall yield of the process are studied; in general, yields are increased by working at low temperature (-60 deg C).Internally substituted olefins are obtained from α-chloro acid chlorides through a similar process.The treatment of α-chloro aldehydes, ketones and carboxylic acid derivatives (esters or acid chlorides) with lithium aluminium hydride or lithium aluminium hydride/aluminium chloride and lithium powder at low temperature (-60 deg C) leads in a regioselective manner to olefins with the same carbon skeleton as the starting carbonyl compound.Reactions with lithium aluminium deuteride lead to incorporation of deuterium at predetermined positions in the alkene.
- Barluenga, Jose,Yus, Miguel,Concellon, Jose M.,Bernad, Pablo
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- Photolysis of 3-Bromo-3-methyldiazirine
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The photolysis at 354 nm of 3-bromo-3-methyldiazirine in gas phase has been studied.After a careful search of the various possibilities we have found that all available evidence points toward the intermediary formation of hot vinyl bromide, presumably via isomerization of the corresponding carbene.Its unimolecular decomposition can take place by two different paths: one is the molecular detachment of HBr and the other the radical scission of the C-Br bond.This last way of radical formation is responsible for the apparently confusing experimental data.According to our result the activation energy for the radical decomposition is closer to that of the molecular detachment than previously thought.
- Crespo, Maria T.,Figuera, Juan M.,Rodriguez, Juan C.,Utrilla, Roberto Martinez
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- Halogenobis(N,N-dialkyldithiocarbamato)iron(III) Complexes as Potential Catalysts for Halogen Addition Reactions to Alkenes
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In the presence of a catalytic amount of iron(III) halogenobisdithiocarbamates, the addition of molecular halogens to alkenes occurs rapidly to afford cis-addition products.
- Tsipis, Constantinos A.,Katsoulos, George A.,Vakoulis, Fotios D.
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- Reactivity of Alkaneselenyl Bromide: Conversion of Alcohols into the Corresponding Alkyl Bromides with Dialkylselenium Dibromide
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The reaction of alcohols with dialkylselenium dibromide gave the corresponding bromides in moderate to high yields.Alkaneselenyl bromide, produced by the thermal decomposition from dialkylselenium dibromide, acts as a brominating agent.The reaction of alcohol with dialkylselenium dichloride afforded the corresponding chlorides, although the yields were realtively low compared with those of the bromide.
- Akabori, Sadatoshi,Takanohashi, Yoshinori
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- Functionalization of saturated hydrocarbons by aprotic superacids 4. Ionic bromination of ethane and other alkanes and cycloalkanes with molecular bromine in the presence of systems based on polyhalomethanes and AlBr3 under mild conditions
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Aprotic organic superacids CBr4 · 2AlBr3, CBr4 · AlBr3, · CCl4 · 2AlBr3, CCl4 · 2AlBr3, and C6F5CF3 · 2AlBr3 efficiently catalyze the bromination of alkanes and cycloalkanes with Br2. Ethane is selectively brominated at 55-65 °C to give mostly 1,2-dibromoethane (stoichiometric reaction). Propane, butane, cyclopentane, cyclohexane, and methyl-cyclopentane react with Br2 at -40 to -20 °C with good selectivity affording monobromides in high yields (catalytic reactions).
- Akhrem,Orlinkov,Afanas'eva,Vol'pin
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- Oxidative bromination of alkenes mediated with nitrite in ionic liquids
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The oxidative bromination of C2-C8 alkenes with HBr-NaNO2-O2 in solutions of BMImBr, HMImBr or BMImBF 4 containing 16-28 wt% H2O was studied using volumetric method, GC-MS analysis, 14N NMR and UV-VIS spectroscopy. The optimal conditions to conduct the reaction at high selectivity for 1,2-dibromoalkanes in BMImBr were determined. The composition of ionic liquid affects the catalytic performance. Although in BMImBF4 the reaction runs with equal rate as in bromide ionic liquid, the fraction of bromohydrin in the reaction products increases to 20 %. Generated from NaNO2, NOx operated as a catalyst in the oxidation of Br- and was oxidized to catalytically inert NO3 - anions when complete conversion of HBr was attained. Graphical Abstract: Oxidative bromination of alkenes [Figure not available: see fulltext.]
- Kuznetsova, Lidia I.,Kuznetsova, Nina I.,Zudin, Vladimir N.,Utkin, Viktor A.,Trebushat, Dmitry V.,Fedotov, Martin A.,Larina, Tatyana V.
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- 1,2-Dibromotetrachloroethane: An efficient reagent for many transformations by modified Appel reaction
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An efficient and facile method has been developed for the synthesis of alkyl bromides from various alcohols under mild conditions using a triphenylphosphine (PPh 3) /1,2-dibromotetrachloroethane (DBTCE) complex in excellent yields and very short time (5 min). This method can also be applied for the transformation of chiral alcohols to their corresponding bromides in very high enantiomeric excess. The PPh 3 /DBTCE complex is also successfully applied to ring-opening reactions of cyclic ethers in mild conditions. Esterification, amidation, and formation of acid anhydrides under very mild experimental conditions are also successfully accomplished by following a modification of the Appel reaction protocol in this work.
- Essiz, Sel?uk,Da?tan, Arif
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p. 150 - 156
(2019/05/16)
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- Formation of acridones by ethylene extrusion in the reaction of arynes with β-lactams and dihydroquinolinones
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N-Unsubstituted β-lactams react with a molecule of aryne by insertion into the amide bond to form a 2,3-dihydroquinolin-4-one, which subsequently reacts with another molecule of aryne to form an acridone by extrusion of a molecule of ethylene. 2,3-Dihydroquinolin-4-ones react under the same reaction conditions to afford identical results. This is the first example of ethylene extrusion in aryne chemistry.
- Fang, Yuesi,Rogness, Donald C.,Larock, Richard C.,Shi, Feng
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scheme or table
p. 6262 - 6270
(2012/09/22)
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- Further insights into the chemistry of niobium and tantalum pentahalides with 1,2-dialkoxyalkanes: Synthesis of bromo- and iodoalkoxides, spectroscopic and computational studies
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The room temperature reactions of a series of 1,2-dialkoxyalkanes ROCH 2CH(R′)OR′′ with MX5 (M = Nb, Ta; X = Br, I) in 1:1 ratio result in single C-O bond cleavage and high-yield formation of the halo-alkoxides MBr4[κ2-OCH 2CH(R′)OR′′] or [NbI4{κ 1-OCH2CH(R′)OR′′}]2, and equimolar amounts of the corresponding alkyl halides RX. The reaction of NbBr5 with 1,2-dimethoxyethane, dme, proceeds with preliminary formation of the ionic species [NbBr4(κ2-dme) (κ1-dme)][NbBr6], 3b, which has been identified by solution NMR at low temperature and conductivity analyses. The gas-phase structure of 3b has been optimized by DFT calculations, confirming that the dme ligands adopt bidentate and monodentate coordination, respectively. Although the formation of NbOBr3(dme), 4b, 1,4-dioxane and MeBr from NbBr 5/dme (ratio 1:2) is an exoergonic process (calculated ΔGr° = -115.96 kcal mol-1), it is inhibited at room temperature. High temperature conditions enhance the production of 1,4-dioxane at the expense of selectivity. The dinuclear species NbOBr3(dme)NbBr5 (Nb-O-Nb), 5b, (X-ray) has been isolated in modest yield as byproduct of the room temperature reaction of NbBr5 with dme. In general, the 1:2 molar reactions of NbX5 (X = Br, I) with ROCH2CH(R′) OR′′ occur with the exclusion of nearly one equivalent of organic reactant.
- Bini, Riccardo,Marchetti, Fabio,Pampaloni, Guido,Zacchini, Stefano
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experimental part
p. 1412 - 1419
(2011/06/22)
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- An economical and convenient synthesis of vinyl sulfones
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A general process for the efficient synthesis of vinyl sulfones has been developed using commercially available sulfinic acid sodium salts and dibromides. A variety of phenyl and methyl vinyl sulfones have been formed in good yields, in the absence of any catalyst. Georg Thieme Verlag Stuttgart.
- Guan, Zheng-Hui,Zuo, Wei,Zhao, Lian-Biao,Ren, Zhi-Hui,Liang, Yong-Min
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p. 1465 - 1470
(2008/02/05)
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- Synthesis of hydroxylated hydrocarbons
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Ethylene glycol, other diols, triols, and polyols are made in an efficient manner by reacting dibromides with water in the presence of a metal oxide. An integrated process of dibromide formation, alcohol synthesis, metal oxide regeneration, and bromine recycling is also provided.
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Page/Page column 5
(2008/06/13)
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- Triphenylphosphine/2,3-dichloro-5,6-dicyanobenzoquinone as a new, selective and neutral system for the facile conversion of alcohols, thiols and selenols to alkyl halides in the presence of halide ions
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A mixture of triphenylphosphine (Ph3P) and 2,3-dichloro-5,6-dicyanobenzoquinone in CH2Cl2 affords a complex which in the presence of R4NX (X=Cl, Br, I) converts alcohols, thiols and selenols into their corresponding alkyl halides in high yields at room temperature. The method is highly selective for the conversion of 1° alcohols in the presence of 2° ones and also 1° and 2° alcohols in the presence of 3° alcohols, thiols, epoxides, trimethylsilyl- and tetrahydropyranyl ethers, 1,3 dithianes, disulfides, and amides.
- Iranpoor,Firouzabadi,Aghapour,Vaez zadeh
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p. 8689 - 8693
(2007/10/03)
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- A facile conversion of thiols to alkyl halides by triphenylphosphine/N-halosuccinimides
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Thiols are efficiently converted to alkyl halides in high to excellent yields when treated with triphenylphosphin/N-halosuccinimide (halogen: Br,Cl, and I) in dichloromethane at room temperature.
- Iranpoor,Firouzabadi,Aghapour
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p. 1176 - 1178
(2007/10/03)
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- 4-substituted piperidine analogs and their use as subtype selective NMDA receptor antagonists
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PCT No. PCT/US96/20872 Sec. 371 Date Sep. 16, 1998 Sec. 102(e) Date Sep. 16, 1998 PCT Filed Dec. 20, 1996 PCT Pub. No. WO97/23216 PCT Pub. Date Jul. 3, 1997Novel 4-substituted piperidine analogs, pharmaceutical compositions containing the same and the method of using 4-substituted piperidine analogs are selective active antagonists of N-methyl-D-aspartate (NMDA) receptor subtypes for treating conditions such as stroke, cerebral ischemia, central nervous system trauma, hypoglycemia, psychosis, anxiety, migraine headaches, glaucoma, CMV retinitis, aminoglycoside antibiotics-induced hearing loss, convulsions, chronic pain, opioid tolerance or withdrawal, urinary incontinence or neurodegenerative disorders, such as lathyrism, Alzheimer's Disease, Parkinsonism and Huntington's Disease are described.
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- Coordination Catalysis in Organic Electrosynthesis. Stoichiometry and Products of Reduction of Dibromomethane by Ni(0) Complexes with π-Acceptor Ligands
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Reaction of Ni(0) complexes with dibromomethane gives different final products depending on the nature of the process in the stage of oxidative addition, which proceeds either through the elimination of two bromide ions to give intermediate carbene, or by the elimination of one bromide ion, depending on the ligand enviroment in the metal complex.
- Budnikova,Petrukhina,Kargin
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p. 257 - 259
(2007/10/03)
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- Palladium(II)-mediated oxidation of alcohols using 1,2-dichloroethane as Pd(0) reoxidant
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The oxidation of primary and secondary, saturated, allylic or benzylic, alcohols is carried out in 1,2-dichloroethane at reflux using catalytic amounts of both PdCl2 and Adogen 464 in the presence of an excess of sodium carbonate. High selectivities are obtained from saturated and benzylic, secondary alcohols. Primary alcohols afford mixtures of aldehydes and esters. The migration of the double bond of α,β-unsaturated alcohols is a competing reaction. It is clearly shown that 1,2-dichloroethane reoxidizes the Pd(0) species.
- Ait-Mohand,Henin,Muzart
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p. 2473 - 2476
(2007/10/02)
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- Imidyl Radicals. The Chemistries of 1,8-Naphthalenedicarboximidyl and Phthalimidyl Radicals
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The chemistries of 1,8-naphthalenedicarboximidyl (N.) and phthalimidyl (P.) radicals are described.Hydrogen abstractions from alkanes and additions to olefins and benzene proceed in high yield.The low cost of phthalimide, coupled with the absence of a parasitic ring-opening reaction for P., makes N-bromophthalimide an economical reagent for low-selectivity brominations.The chemistry of N. resembles that of other imidyl radicals (succinimidyl, glutarimidyl) with respect to selectivities.Conversely, P. is somewhat of a maverick among imidyl radicals, being slightly more selective in its reactions, but still 102-103 less selective than Br..
- Day, J. C.,Govindaraj, N.,McBain, D. S.,Skell, P. S.,Tanko, J. M.
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p. 4959 - 4963
(2007/10/02)
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- PARTICIPATION OF SULFONATE IONS IN THE ELECTROPHILIC ADDITION OF HALOGENS TO OLEFINS
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The reactions of ethylene, 1-heptene, cyclohexene, and styrene with chlorine and bromine in methylene chloride and chloroform in the presence of tetrabutylammonium p-toluenesulfonate and tetrabutylammonium methanesulfonate were investigated.In all cases the 2-halogenoalkyl esters of the sulfonic acids were obtained with comparable yields in addition to the 1,2-dihalides.The addition of chlorine and bromine to cyclohexene and also of bromine to 1-heptene in acetic acid in the presence of lithium p-nitrobenzenesulfonate leads to 2-halogenoalkyl esters of the sulfonicacids and acetic acid in addition to the 1,2-dihalides.These data indicate concurrent combination of the sulfonate anions at the concluding stage of AdE reactions.The mechanistic aspects and consequences of this effect are discussed.
- Zefirov, N. S.,Koz'min, A. S.,Dan'kov, Yu. V.,Zhdankin, V. V.,Kirin, V. N.
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p. 205 - 213
(2007/10/02)
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- Synthesis, N.m.r. Spectra, and Structure of Macrocyclic Compounds containing the Ferrocene Unit
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The condensation of 1,1'-bis(chlorocarbonyl)ferrocene with diaza-18-crown-6 gives 1,1'-(1,4,10,13-tetraoxa-7,16-diazacyclo-octadecane-7,16-diyldicarbonyl)ferrocene (5) together with its dimer 1,1'':1',1'''-bis-(1,4,10,13-tetraoxa-7,16-diazacyclo-octadecane-7,16-diyldicarbonyl)bisferrocene (6) and the separation and isolation of these compounds are described.High resolution 1H and 13C n.m.r. spectra using homo- and hetero-nuclear decoupling techniques allow a complete assignment of the spectral data for (5) and (6) and lead to a proposal of a structure for (5) involving a trans-disposition of the amide carbonyl groups.Variable-temperature n.m.r. data on (6) reveal two distinct dynamic processes within the molecule involving rotation about the ferrocene-carbonyl bond (ΔG=50 kJ mol-1, Tc=-10 deg C) and rotation about the N-CO bond (ΔG=67 kJ mol-1, Tc=+60 deg C).The preparation, 1H and 13C n.m.r. data of monocyclic compounds containing the ferrocene unit (13a-c), (14) and (15) are also described and the details of the synthesis of an 15N-labelled analogue of (13c), the macrocycle (16), are reported.
- Hammond, Philip J.,Bell, Alan P.,Hall, C. Dennis
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p. 707 - 715
(2007/10/02)
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- Ambident Electrophilic Character of Thioxophosphoranesulphenyl Bromides =P(S)SBr. A Novel Observation of Electrophilic Addition to a Carbon-Carbon Double Bond
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The thioxophosphoranesulphenyl bromides (1) act as ambident electrophiles towards alkenes and react, depending on the structure of the alkene, to give either the normal addition products -SC(R1)(R2)CR3(R4)(Br) or 1,2-dibromides and -disulphides.
- Lopusinski, Andrzej,Michalski, Jan,Potrzebowski, Mark
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p. 1362 - 1364
(2007/10/02)
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- Lithium Perchlorate as a Reagent for Synthesis of Covalently Bonded Organic Perchlorates via Electrophilic Additions of Halogens and Nitronium Tetrafluoroborate to Olefins
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The reaction of a series of olefins with chlorine and bromine in the presence of a large excess of lithium perchlorate in ether gave 1,2-halo perchlorates together with the corresponding 1,2-dihalides.Analogous reactions of NO2BF4 in methylene chloride or ethyl acetate with monoolefins gave 1,2-nitro perchlorates.Norbornadiene reacted with a NO2BF4/LiClO4 system to give two isomeric nitro perchlorates of nortricyclenic structure.Several synthetic and mechanistic aspects of this new reaction of electrophilic perchloration of olefins are discussed.
- Zefirov, N.S.,Koz'min, A.S.,Zhdankin, V.V.,Nikulin, A.V.,Zyk, N.V.
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p. 3679 - 3684
(2007/10/02)
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- KETTENVERLAENGERUNG DURCH CARBONYLINSERTION BEI DER REAKTION VON (TETRACARBONYL)-(OLEFIN)EISEN(O)-KOMPLEXEN MIT OXIDATIONSMITTELN
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On oxidation of (tetracarbonyl)(olefin)iron(O)-complexes in alcoholic solvents esters carrying a substituent in the 3-position are formed by a carbonylinsertion reaction.
- Schmidt, E. K. G.,Wiese, W.
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p. 4425 - 4428
(2007/10/02)
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- 4-PYRIMIDONE COMPOUNDS
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The compounds are substituted isocytosines which are histamine H 2-antagonists. Two specific compounds of the present invention are 2-2-(5-methyl-4-imidazolylmethylthio)-ethylamino!-5-(3-methoxybenzyl)-4-pyrim idone and 2-2-(5-methyl-4-imidazolylmethylthio)ethylamino!-5-benzyloxy-4-pyrimidone.
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- Synthesis of aldehydes and products of such synthesis
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The disclosure describes the production of complex aliphatic, unsaturated and cycloalkane aldehydes utilizing heterocyclic ring compounds, such as oxazines, particularly dihydro-1,3-oxazines. The oxazines are treated with an alkali metal-alkane compound, such as butyl lithium in the presence of an organic solvent at subzero temperature to form an anion of the oxazine. This anion is then alkylated in the anhydrous reaction mixture by introduction of a suitable halide, epoxide or ketone while still at a subzero temperature and mixture is permitted to warm up to room temperature, following which the reaction mixture is acidified, as with hydrochloric acid to pH 2 to 3, extracted and then made basic, as with caustic alkali with cooling. The reaction mixture is then extracted, as with ether, to produce after evaporation the alkylated dihydro-1,3-oxazine. The alkylated dihydro-1,3-oxazine is then reacted with an alkali metal or sodium borohydride or borodeuteride or borotritide, with cooling to subzero temperatures at about a neutral pH and then transferred into a basic aqueous environment following extraction of the aqueous layer with an organic solvent, such as ether, to give a tetrahydro-1,3-oxazine. This compound may then be converted to the aldehyde desired by steam distillation or by hydrolysis in the presence of a dilute or weak acid, such as hydrochloric or oxalic acid. The aldehydes may then be extracted. These aldehydes are useful as components or intermediates in flavoring or perfumes, in insect attractants and repellants, and in pharmaceuticals.
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- Divinyl stilbenes as optical brighteners
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Disclosed are compounds of formula I STR1 in which R1 and R4, independently, are hydrogen, a non-chromophoric second order substituent, or alkyl or alkenyl unsubstituted or substituted by a non-chromophoric group, R2 and R5, independently, are hydrogen or alkyl or alkenyl, unsubstituted or substituted by a non-chromophoric group, R3 and R6, independently, are hydrogen, alkyl, carboxyl or a non-chromophoric esterified carboxyl group, or R2, together with R3, and/or R5 together with R6, signify an alkylene bridge, R7 and R8, independently, signify hydrogen or a non-chromophoric substituent, or, when R7 is in the 3-position and/or R8 in the 3' position, R7 together with R2, and/or R8 together with R5 signify an alkylene bridge, With the proviso that no more than one of R1 and R2 and no more than one of R4 and R5 signify hydrogen, their production and use as optical brightening agents.
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- ALKOXY PYRIDINE COMPOUNDS
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The compounds are alkoxypyridine compounds which are histamine H 2-antagonists. Two specific compounds of the present invention are N-cyano-N'-methyl-N"-2-((3-methoxy-2-pyridyl)methylthio)ethyl!guanidine and 1-methylamino-1-2-(3-methoxy-2-pyridyl)methylthio)ethylamino!-2-nitroethylene. "
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- Propynyl benzyl ethers
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Propynyl benzyl ethers having juvenile hormone-like activity which are 4-halogen, lower alkyl, lower alkoxy or propynyloxy substituted or 3,4-lower alkylenedioxy substituted and which can also be 3,5- and/or α-substituted, and insecticide compositions that include at least one propynyl benzyl ether and that can also include a conventional insect-poison.
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