- Kinetics of 'initial burst' in the solid-liquid phase-transfer catalysis. Nucleophilic substitution of 2-octyl mesylate with potassium bromide
-
The SN2 substitution of 2-octyl mesylate with solid KBr under the conditions of phase-transfer catalysis was studied kinetically using the model approach of 'initial burst.' It is suggested that such kinetics reflect the contribution of mass transfer and surface poisoning. The proposed model is used to explain the influences of catalyst, solvent, stirring speed, activation and agitation effects. The mechanistic scheme suggests that the reaction is described by two separate kinetic stages, one of which reflects the intrinsic rate-limited step and the other the mass transfer-controlled step. Copyright
- Yufit,Zinovyev
-
-
Read Online
- An Unusually Mild and Selective Bromination of Some n-Alkanes with Barium Tetrafluorobromate
-
Abstract: Barium tetrafluorobromate Ba(BrF4)2 is a brominating agent for hexane, octane, and decane. The reaction occurs under very mild conditions at –25 to –20°C and results in preferential formation of 2-bromoalkanes.
- Sobolev,Ostvald,Zherin,Shushpanova,Filimonov
-
p. 297 - 299
(2021/03/26)
-
- Construction of chiral liquid crystal phosphorescent material based on cyclometalated platinum complex and application of chiral liquid crystal phosphorescent material in circular polarizer
-
The invention discloses a chiral liquid crystal luminescent material based on a cyclometalated platinum complex and application of the chiral liquid crystal luminescent material. According to the invention, the cyclometalated platinum complex is used as a light-emitting core, and chiral alkyl chains and liquid crystal elements are respectively introduced to the peripheries of a main ligand and anauxiliary ligand to construct the chiral liquid crystal phosphorescent material. The material shows effective circular polarization luminescence performance in a solid film. The cyclometalated platinum complex is used as a doping agent of a light-emitting layer; a circular polarization organic light-emitting device is prepared through a solution method, the maximum external quantum efficiency is 11.3%, and the maximum electrogenerated circular polarization light-emitting asymmetry factor (glum) is 0.06; and the annealing temperature of the light-emitting layer has great influence on the circular polarization light-emitting performance of the device. The invention provides a research thought for constructing the efficient chiral liquid crystal phosphorescent material.
- -
-
Paragraph 0021
(2020/06/09)
-
- Sodium diisopropylamide-mediated dehydrohalogenations: Influence of primary- A nd secondary-shell solvation
-
Eliminations of alkyl halides by sodium diisopropylamide (NaDA) in tetrahydrofuran (THF)/hexane or THF/N,N-dimethylethylamine (DMEA) solutions are facile and complementary to analogous reactions of lithium diisopropylamide in THF. Rate studies show a dominance of monomer-based metalations and prevalent secondary-shell solvation effects overlaid on primary-shell effects. 1-Halooctanes exclusively undergo elimination rather than substitution. Rate and isotopic labeling studies on 1-bromooctane reveal an E2-like elimination pathway via trisolvated NaDA monomer. By contrast, 1-chlorooctane is eliminated via disolvated monomer through a carbenoid mechanism. exo-2-Norbornyl chloride and bromide are also eliminated via disolvated monomer; a syn E2 mechanism is inferred for these substrates. The cis- A nd trans-4-tert-butylcyclohexyl bromides show a preference for the elimination of the cis isomer (kcis/ax/ktrans/eq = 10). Rate and isotopic labeling studies are consistent with a trans-diaxial E2 elimination via trisolvated monomer for the cis isomer and a carbenoid mechanism via disolvated monomer for the trans isomer. Vicinal haloethers show substrate-dependent reactivities, affording alkynes and enol ethers. trans-1-Bromo-2-methoxycyclohexane provides enol ether 1-methoxycyclohexene, while trans-1-bromo-2-methoxycyclooctane provides dimeric products consistent with fleeting cycloocta-1,2-diene (cyclic allene), which was fully characterized as two conformers.
- Ma, Yun,Algera, Russell F.,Woltornist, Ryan A.,Collum, David B.
-
supporting information
p. 10860 - 10869
(2019/09/30)
-
- Palladium-Catalyzed Alkoxycarbonylation of Unactivated Secondary Alkyl Bromides at Low Pressure
-
Catalytic carbonylations of organohalides are important C-C bond formations in chemical synthesis. Carbonylations of unactivated alkyl halides remain a challenge and currently require the use of alkyl iodides under harsh conditions and high pressures of CO. Herein we report a palladium-catalyzed alkoxycarbonylation of secondary alkyl bromides that proceeds at low pressure (2 atm CO) under mild conditions. Preliminary mechanistic studies are consistent with a hybrid organometallic-radical process. These reactions efficiently deliver esters from unactivated alkyl bromides across a diverse range of substrates and represent the first catalytic carbonylations of alkyl bromides with carbon monoxide.
- Sargent, Brendon T.,Alexanian, Erik J.
-
supporting information
p. 7520 - 7523
(2016/07/06)
-
- A mild method for the replacement of a hydroxyl group by halogen. 1. Scope and chemoselectivity
-
α-Chloro-, bromo- and iodoenamines, which are readily prepared from the corresponding isobutyramides have been found to be excellent reagents for the transformation of a wide variety of alcohols or carboxylic acids into the corresponding halides. Yields are high and conditions are very mild thus allowing for the presence of sensitive functional groups. The reagents can be easily tuned allowing therefore the selective monohalogenation of polyhydroxylated molecules. The scope and chemoselectivity of the reactions have been studied and reaction mechanisms have been proposed.
- Munyemana, Fran?ois,George, Isabelle,Devos, Alain,Colens, Alain,Badarau, Eduard,Frisque-Hesbain, Anne-Marie,Loudet, Aurore,Differding, Edmond,Damien, Jean-Marie,Rémion, Jeanine,Van Uytbergen, Jacqueline,Ghosez, Léon
-
p. 420 - 430
(2015/12/31)
-
- An efficient and selective method for the iodination and bromination of alcohols under mild conditions
-
A straightforward and effective procedure for the conversion of a variety of alcohols into the corresponding alkyl iodides and bromides is described using KX/P2O5 (X = I, Br). The reactions were easily carried out in acetonitrile under mild conditions. Using this method, the selective conversion of benzylic alcohols in the presence of aliphatic alcohols was achieved.
- Khazdooz, Leila,Zarei, Amin,Aghaei, Hamidreza,Azizi, Ghobad,Gheisari, Mohammad Mehdi
-
p. 168 - 171
(2015/12/30)
-
- Tribromoisocyanuric acid/triphenylphosphine: A new system for conversion of alcohols into alkyl bromides
-
An efficient and facile method has been developed for the conversion of alcohols into alkyl bromides under neutral conditions using tribromoisocyanuric acid and triphenylphosphine (molar ratio 1.0:0.7:2.0, alcohol/ tribromoisocyanuric acid/triphenylphosphine) in dichloromethane at room temperature. This method can be applied for the conversion of primary, secondary, benzylic and allylic alcohols, and their corresponding bromides are obtained in 67-82 percent yield. Tertiary alcohols do not react under these conditions.
- De Andrade, Vitor S.C.,De Mattos, Marcio C.S.
-
p. 975 - 979
(2014/06/24)
-
- Copper-catalyzed alkyl-alkyl cross-coupling reactions using hydrocarbon additives: Efficiency of catalyst and roles of additives
-
Cross-coupling of alkyl halides with alkyl Grignard reagents proceeds with extremely high TONs of up to 1230000 using a Cu/unsaturated hydrocarbon catalytic system. Alkyl fluorides, chlorides, bromides, and tosylates are all suitable electrophiles, and a TOF as high as 31200 h-1 was attained using an alkyl iodide. Side reactions of this catalytic system, i.e., reduction, dehydrohalogenation (elimination), and the homocoupling of alkyl halides, occur in the absence of additives. It appears that the reaction involves the β-hydrogen elimination of alkylcopper intermediates, giving rise to olefins and Cu-H species, and that this process triggers both side reactions and the degradation of the Cu catalyst. The formed Cu-H promotes the reduction of alkyl halides to give alkanes and Cu-X or the generation of Cu(0), probably by disproportionation, which can oxidatively add to alkyl halides to yield olefins and, in some cases, homocoupling products. Unsaturated hydrocarbon additives such as 1,3-butadiene and phenylpropyne play important roles in achieving highly efficient cross-coupling by suppressing β-hydrogen elimination, which inhibits both the degradation of the Cu catalyst and undesirable side reactions.
- Iwasaki, Takanori,Imanishi, Reiko,Shimizu, Ryohei,Kuniyasu, Hitoshi,Terao, Jun,Kambe, Nobuaki
-
p. 8522 - 8532
(2015/01/08)
-
- In situ generated Ph3P(OAc)2as a novel reagent for the efficient acetylation of alcohols and thiols at room temperature
-
Ph3P, Br2, and ammonium acetate are used for the in situ generation of Ph3P(OAc)2, which was characterized by different NMR techniques. The Ph3P(OAc)2generated was used as a novel and efficient reagent for the acetylation of alcohols and thiols in acetonitrile at room temperature under homogeneous conditions. This reaction was also performed under heterogeneous conditions using 1,3,2,4- diazadiphosphetidine as an easily prepared, stable, and heterogeneous P(III) compound.
- Iranpoor, Nasser,Firouzabadi, Habib,Elham, Etemadi Davan
-
p. 1813 - 1816
(2013/04/24)
-
- Synthesis of silica bromide as heterogeneous reagent and its application to conversion of alcohols to alkyl bromides
-
Silica bromide as heterogeneous reagent is prepared from the reaction of silica gel with PBr3 as a nonhydroscopic, filterable, cheap, and stable yellowish powder that can be stored for months. The results show that the silica bromide is a suitable and efficient reagent for conversion of alcohols to alkyl bromides under mild conditions at room temperature. The easy availability of this reagent makes this simple procedure attractive and a practical alternative to the existing methods.
- Mohanazadeh, Farajollah,Sedrpoushan, Alireza,Zolfigol, Mohammad A.,Veisi, Hojat
-
p. 598 - 603,6
(2012/12/11)
-
- A facile and green protocol for nucleophilic substitution reactions of sulfonate esters by recyclable ionic liquids [bmim][X]
-
Ionic liquids [bmim][X] (X = Cl, Br, I, OAc, SCN) are highly efficient reagents for nucleophilic substitution reactions of sulfonate esters derived from primary and secondary alcohols. The counter anions (X-) of the ionic liquids, [bmim][X], effectively replace the sufonates affording the corresponding substitution products such as alkyl halides, acetates, and thiocyanides in excellent yields. The newly developed protocol is very environmentally attractive because the reactions use stoichiometric amounts of ionic liquids as sole reagents in most cases and do not require additional solvents, any other activating reagents, non-conventional equipment, or special precautions. Moreover, these ionic liquids can be readily recycled without loss of reactivity, making the whole process greener.
- Liu, Yajun,Xu, Yongnan,Jung, Sun Ho,Chae, Junghyun
-
p. 2692 - 2698,7
(2012/12/12)
-
- A facile and green protocol for nucleophilic substitution reactions of sulfonate esters by recyclable ionic liquids [bmim][X]
-
Ionic liquids [bmim][X] (X = Cl, Br, I, OAc, SCN) are highly efficient reagents for nucleophilic substitution reactions of sulfonate esters derived from primary and secondary alcohols. The counter anions (X-) of the ionic liquids, [bmim][X], effectively replace the sufonates affording the corresponding substitution products such as alkyl halides, acetates, and thiocyanides in excellent yields. The newly developed protocol is very environmentally attractive because the reactions use stoichiometric amounts of ionic liquids as sole reagents in most cases and do not require additional solvents, any other activating reagents, non-conventional equipment, or special precautions. Moreover, these ionic liquids can be readily recycled without loss of reactivity, making the whole process greener. Georg Thieme Verlag KG Stuttgart · New York.
- Liu, Yajun,Xu, Yongnan,Jung, Sun Ho,Chae, Junghyun
-
p. 2692 - 2698
(2013/01/15)
-
- Efficient procedures to prepare primary and secondary alkyl halides from alkanols via the corresponding sulfonates under mild conditions
-
The study presented herein shows that sulfonate/halide exchange can be advantageously performed in THF to avoid several side reactions such as elimination and epimerization when the reaction is performed from a chiral alkyl sulfonate or a substrate having a C-H acidic chiral center. The main limitation of this procedure was found to be the conversion of secondary alkyl sulfonates to alkyl chlorides. In this case, the addition of a catalytic amount of manganese chloride clearly accelerates the rate and the efficiency of the reaction. Copyright
- Cahiez, Gerard,Gager, Olivier,Moyeux, Alban,Delacroix, Thomas
-
supporting information; experimental part
p. 1519 - 1528
(2012/07/03)
-
- Catalytic distillation process for primary haloalkanes
-
A process for making primary haloalkanes by catalytic distillation of internal haloalkanes which comprises a) introducing an internal haloalkane feed into a catalytic distillation column; b) isomerizing at least a portion of the internal haloalkane feed in the presence of an internal haloalkane isomerization catalyst at a temperature at or above the boiling point of the internal haloalkanes and below the temperature and pressure at which hydrogen halide is formed to form primary haloalkanes; and removing the primary haloalkanes from the catalytic distillation column.
- -
-
Page/Page column 9-10
(2012/02/17)
-
- Silver-catalyzed benzylation and allylation of tertiary alkyl bromides with organozinc reagents
-
Silver salts catalyze the benzylation and allylation of tertiary alkyl bromides with organozinc reagents. The reactions create quaternary carbon centers efficiently. Treatment of gem-dibromoalkanes with benzylic or allylic zinc reagents under silver catalysis leads to dibenzylation or diallylation. The functional-group compatibility of the present reactions is wider than that of the previous reactions with Grignard reagents.
- Mitamura, Yukihiro,Asada, Yoshihiro,Murakami, Kei,Someya, Hidenori,Yorimitsu, Hideki,Oshima, Koichiro
-
experimental part
p. 1487 - 1493
(2011/07/07)
-
- Highly efficient oxidative bromination of alkanes with the HBr-H 2O2 system in the presence of catalyst
-
Various cycloalkanes and straight-chain alkanes were efficiently brominated with an aqueous HBr-H2O2 system. This oxidative brominating process was promoted by catalysis and irradiation with light. The cycloalkanes were converted to the corresponding bromo-cycloalkanes in moderate yields and the straight-chain alkanes produced dominantly secondary bromides. This simple but effective bromination method of alkanes is characterized by high atom efficiency, inexpensive reagents and the absence of organic waste, which make it a good alternative to the existing method for Ci£H activation through bromination. A simple, effective, environmentally friendly method was researched for bromination of alkanes in good yield with HBr as the origin of bromine.
- Li, Yujin,Ju, Jie,Jia, Jianhong,Sheng, Weijian,Han, Liang,Gao, Jianrong
-
experimental part
p. 2428 - 2432
(2011/10/03)
-
- Hexabromoacetone and ethyl tribromoacetate: a highly efficient reagent for bromination of alcohol
-
A new and efficient method for the bromination of alcohols utilizing Br3CCOCBr3/PPh3 and Br3CCO2Et/PPh3 is described. Various alcohols can be converted smoothly into their corresponding alkyl bromides in high yields under mild conditions with short reaction times. Based upon 1H NMR studies using competitive reactions between selected brominating agents and Cl3CCN, Br3CCOCBr3 displays the highest reactivity approximately nine times that of CBr4.
- Tongkate, Pratoomrat,Pluempanupat, Wanchai,Chavasiri, Warinthorn
-
p. 1146 - 1148
(2008/09/18)
-
- Facile conversion of alcohols into their bromides and iodides by N-bromo and N-iodosaccharins/triphenylphosphine under neutral conditions
-
N-Bromo and N-iodosaccharins in the presence of triphenylphosphine convert alcohols into the corresponding bromides and iodides in good to excellent yields at room temperature under neutral conditions.
- Firouzabadi, Habib,Iranpoor, Nasser,Ebrahimzadeh, Farzaneh
-
p. 1771 - 1775
(2007/10/03)
-
- 4-Aminophenyldiphenylphosphinite (APDPP), a new heterogeneous and acid scavenger phosphinite - Conversion of alcohols, trimethylsilyl, and tetrahydropyranyl ethers to alkyl halides with halogens or N-halosuccinimides
-
A new heterogeneous phosphinite, 4-aminophenyldiphenylphosphinite (APDPP), is prepared and used for the efficient conversion of alcohols, trimethylsilyl ethers, and tetrahydropyranyl ethers to their corresponding bromides, iodides, and chlorides in the presence of molecular halogens or N-halosuccinimides. The amino group in this phosphinite acts as an acid scavenger and removes the produced acid. A simple filtration easily removes the phosphinate by-product.
- Iranpoor, Nasser,Firouzabadi, Habib,Gholinejad, Mohammad
-
p. 1006 - 1012
(2007/10/03)
-
- A new diphenylphosphinite ionic liquid (IL-OPPh2) as reagent and solvent for highly selective bromination, thiocyanation or isothiocyanation of alcohols and trimethylsilyl and tetrahydropyranyl ethers
-
A new diphenylphosphinite ionic liquid (IL-OPPh2) is introduced. This ionic liquid is used as both a reagent and a solvent to convert alcohols and trimethylsilyl and tetrahydropyranyl (THP) ethers into their corresponding alkyl bromides, thiocyanates or isothiocyanates in the presence of Br2 and SCN- at 80 °C. In this ionic liquid, bromination and thiocyanation of alcohols occurs highly selectively in the presence of trimethylsilyl and THP-ethers and also between different classes of alcohols. The use of this ionic liquid allows easy separation of the desired products from the phosphinate by-product.
- Iranpoor, Nasser,Firouzabadi, Habib,Azadi, Roya
-
p. 5531 - 5534
(2007/10/03)
-
- Silicaphosphine (Silphos): A filterable reagent for the conversion of alcohols and thiols to alkyl bromides and iodides
-
Silicaphosphine (Silphos), [P(Cl)3-n(SiO2) n], as a new heterogeneous reagent is introduced. This reagent converts alcohols and thiols to their corresponding bromides and iodides in the presence of X2 (X=Br, I) in refluxing CH3CN in high to quantitative yields. Use of Silphos provides a highly practical method for the easy separation of the Silphos oxide byproduct by a simple filtration.
- Iranpoor, Nasser,Firouzabadi, Habib,Jamalian, Arezu,Kazemi, Foad
-
p. 5699 - 5704
(2007/10/03)
-
- Conversion of alcohols to bromides using a fluorous phosphine
-
Reaction of alcohols with the fluorous phosphine-carbon tetrabromide complex in toluene or in a two-phase toluene-FC-72 system afforded the corresponding bromides in good yields. The fluorous-phosphine oxide is readily separated by liquid-liquid extraction, providing an alternative to the homogeneous triphenylphosphine-carbon tetrachloride conversion, as well as to the polymer-supported phosphine method. The fluorous phosphine oxide could be reduced and the product reused.
- Desmaris, Laurence,Percina, Nathalie,Cottier, Louis,Sinou, Denis
-
p. 7589 - 7591
(2007/10/03)
-
- A comparative kinetic study of nucleophilic substitution under PTC conditions in liquid-liquid and solid-liquid systems
-
The phenomenon of initial exponential burst (IB) on kinetic curves in the reaction with solid salts was observed in the study on the S(N)2 substitution reaction of 2-octylmesylate with potassium halides under phase- transfer catalysis (PTC) conditions in liquid-liquid (l/l) and solid-liquid (s/l) systems. The mechanistic scheme describing the IB phenomenon in application to s/l PTC has been developed from the analysis of IB kinetic model known in enzyme kinetics.
- Yufit, Sergei S.,Zinovyev, Sergei S.
-
p. 6319 - 6328
(2007/10/03)
-
- Kinetics of SN2 substitution reactions under conditions of phase-transfer catalysis in the systems liquid-liquid and liquid-solid. Initial jump phenomenon in reactions with solid salt
-
Comparative study of the kinetics of substitution of the mesyl group in 1-methylheptyl methanesulfonate by halogen under conditions of phase-transfer catalysis in the two-phase systems liquid-liquid and liquid-solid has revealed an initial jump on the kinetic curves for the liquid-solid system. Such phenomenon has been known previously for some complex enzymatic reactions but unknown for phase-transfer reactions. Parameters of the initial jump on kinetic curves allow one to draw some conclusions on the reaction mechanism in the system liquid-solid. The effect of reactant concentrations and temperature on the initial jump parameters has been estimated for the first time.
- Yufit,Zinov'ev
-
p. 1222 - 1225
(2007/10/03)
-
- Halide assisted addition of hydrogen halides to alkenes
-
The addition of 0.1 M quaternary ammonium halide to a solution of 20% trifluoroacetic acid in methylene chloride causes a large rate increase in the reaction of simple alkenes leading to a mixture of alkyl halides and trifluoroacetates. The mechanism is proposed to involve a halide assisted protonation of the alkene which produces a carbocation intermediate sandwiched between the attacking halide ion and the trifluoroacetate ion. At higher concentrations of halide ion, the proton donating ability of the solution decreases, slowing the reaction and increasing the efficiency of cation capture by the halide ion. This leads to a greater proportion of unrearranged halide product. At the highest concentration of halide ion, cation rearrangement is virtually eliminated.
- Weiss, Hilton M.,Touchette, Kim M.
-
p. 1517 - 1522
(2007/10/03)
-
- Formation of three-membered rings by SHi displacement. Reverse of cyclopropyl ring opening
-
The general methods, photoinitiated or peroxide-initiated free radical chain additions of halomethanes to olefins, yield 1,2-addition products at temperatures ranging from 20 to 100°C. At lower temperatures, -42 to -104°C, a competitive reaction, subsequent to the addition of CCl2X., yields alkylcyclopropanes. The reactions of 1-octene or 1-hexene and 1-methylcyclohexene with atomic hydrogen carried out in the presence of several transfer agents (CCl4, CCl3Br, CCl2Br2) initiate a radical chain addition of CCl2X. and yield cyclized materials resulting from the SHi displacement of halogen by a carbon-centered radical. The radical displacement of a halogen on carbon, the reverse of homolytic displacement on cyclopropyl carbon, is dominant at low temperatures. The rate constants for cyclization (kc) vs transfer with halomethane (kt) showed isokinetic temperatures of -46°C (CCl4, 1-hexene); -35°C (CCl4, 1-methylcyclohexene). The isokinetic temperatures for the reactions of the two substrates carried out in the presence of BrCCl3 were calculated as -204 °C (1-octene) and -109°C (1-methylcyclohexene).
- Tanner, Dennis D.,Zhang, Liying,Hu, Li Qing,Kandanarachchi, Pramod
-
p. 6818 - 6824
(2007/10/03)
-
- A Convenient Conversion of Primary Amines into the Corresponding Halides Radical Promoted Halodeamination via N-Substituted-N-Tosylhydrazines
-
Treatment of 1-substituted-1-tosylhydrazines with 2 equivalents of NCS or NBS in dry THF in presence of light affords the corresponding alkyl halides in good yields.This reaction presumably involves the initial formation of a stabilized hydrazyl radical which is halogenated in a radical chain process.Elimination of p-toluenesulfinic acid and extrusion of nitrogen leads to the corresponding alkyl halide.This route provides an improved method for halodeamination under neutral reaction conditions.
- Collazo, Luis R.,Guziec, Frank S.,Hu, Wei-Xiao Jr.,Pankayatselvan, Ratnadevi
-
p. 7911 - 7914
(2007/10/02)
-
- REGIOSPECIFIC AND STEREOSPECIFIC SUBSTITUTION OF HYDROXYL IN ALIPHATIC ALCOHOLS BY HALOGEN
-
A new system containing triphenylphosphine and trichloro- and tribromoacetic ester makes it possible to substitute the hydroxyl group in alcohols by halogen.Regiospecific and stereospecific substitution of the hydroxyl by the halogen takes place as a result of the reaction of primary and secondary aliphatic alcohols and of 2-alkenols, susceptible to isomerization processes, with this system.
- Matveeva, E. D.,Kurts, A. L.,Yalovskaya, A. I.,Nikishova, N. G.,Bundel', Yu. G.
-
p. 642 - 646
(2007/10/02)
-
- SYNTHESIS OF ALKYL HALIDES UNDER NEUTRAL CONDITIONS
-
Primary and secondary alcohols are efficiently converted to the corresponding alkyl halides under neutral conditions.
- Munyemana, Francois,Frisque-Hesbain, Anne-Marie,Devos, Alain,Ghosez, Leon
-
p. 3077 - 3080
(2007/10/02)
-
- ORGANOBORANES FOR SYNTHESIS. 10. THE BASE-INDUCED REACTION OF BROMINE WITH ORGANOBORNES. A CONVENIENT PROCEDURE FOR THE CONVERSION OF ALKENES INTO ALKYL BROMIDES VIA HYDROBORATION
-
The reaction of trialkylboranes with bromine is greatly accelerated by base.Bromination in the presence of sodium hydroxide provides alkyl bromide along with a large amount of the corresponding alcohol.The use of sodium methoxide as a base eliminates this undesirable side reaction and provides an improved yield of alkyl bromide.Consequently, hydroboration, followed by bromination in the presence of sodium methoxide, provides a convenient new procedure for the conversion of alkenes into alkyl bromides.The organoboranes, obtained via hydroboration of terminal alkenes, react with the utilization of all three alkyl groups attached to boron, providing nearly quantitative yields of alkyl bromides. This procedure also accommodates common organic functional groups, as demonstrated by the preparation of methyl 11-bromoundecanoate and 11-bromoundecyl acetate from the corresponding functionally substituted alkenes.Under these conditions, secondary and bulky primary alkyl groups react more sluggishly.However, a procedure involving simultaneous addition of bromine and methanolic sodium methoxide provides improved results for such derivatives.Surprisingly, the base-induced bromination of tri-exo-nobornylborane results in an inversion of configuration at the reaction center to give predominantly endo-2-bromonorbornane.A mechanism is proposed to account for this remarkable inversion.
- Brown, Herbert C.,Lane, Clinton F.
-
p. 2763 - 2772
(2007/10/02)
-
- Triphase Catalytic Conversion of Alkenes to Organic Halides
-
Reactions of alkenes with hydrohalogenic acids (HCl and HBr) have been studied in the presence of polystyrylmethylenehexadecylbutylphosphonium bromide (1) and polystyrylmethylenehexadecyldiphenylphosphonium bromides (2) as triphase catalysts to yield organic halides by a simple product isolation.The catalysts could be recovered and recycled without loss of activity
- Khurana, Jitender M.,Tetenyi, Peter,Kodomari, Mitsuo,Regen, Steven L.
-
p. 1129 - 1130
(2007/10/02)
-
- CONVERSION OF ALCOHOLS INTO ALKYL BROMIDES AND IODINES VIA O-ALKYLISOUREAS
-
Treatment of O-alkylisoureas with trifluoromethanesulphonic acid and a tetrabutylammonium salt (bromide or iodide) affords alkyl halides in high yields.
- Collingwood, Stephen P,Davies, Alan P,Golding, Bernard T
-
p. 4445 - 4448
(2007/10/02)
-
- 1,2-BIS (DIPHENYLPHOSPHINO)ETHANE TETRAHALIDE: A CONVENIENT REAGENT FOR THE CONVERSION OF ALCOHOLS TO THE CORRESPONDING HALIDES
-
Efficient and rapid conversion under mild conditions of various alcohols and tetrahydro-2-pyranyl (THP) protected alcohols into the corresponding halide (Br or I) are described using the corresponding 1,2-bis (triphenylphosphino)ethane tetrahalide.Tert-butyldimethylsilyl ethers, esters and olefins are stable to these conditions.
- Schmidt, Steven P.,Brooks, Dee W.
-
p. 767 - 768
(2007/10/02)
-
- The Synthesis of (E)-7-Methyl-tridec-6-en-1-ol: A Comparative Study on the Stereoselective Synthesis of (E)-Trisubstituted Double Bonds
-
Several routes to (E)-7-methyltridec-6-en-1-ol (2) have been carried out in order to present a useful comparative study on the stereoselective synthesis of (E)-trisubstituted double bonds.Di-n-pentyl-lithiumcuprate addition to four different allylic systems gave (2), after depyranylation, with E Z selectivities ranging from 3:1 to 40:1 depending on the nature and the position of the leaving group.
- Bernardi, Anna,Cabri, Walter,Poli, Giovanni,Prati, Laura
-
p. 701 - 717
(2007/10/02)
-
- A CONVENITENT PREPARATION OF ALKYL HALIDES AND CYANIDES FROM ALCOHOLS BY MODIFICATION OF THE MITSUNOBU PROSCEDURE
-
Alakanols are converted to the corresponding halides and cyanides with inversion of configuration by lithium salts in combination with a preformed complex of diethyl azodicarboxylate and triphenylphosphine.
- Manna, Sukumar,Falck, J. R.,Mioskowski, Charles
-
p. 663 - 668
(2007/10/02)
-
- Solvent and Counterion Effects on the Stereochemistry and the Competition between Electron-Transfer and SN2 Mechanisms in the Reaction of (Trimethylstannyl)alkalies with Bromides
-
Recations of (trimethylstannyl)alkalies (Me3SnM, M=Li, Na, K) with bromides have been studied in solvents including tetraglyme and tetrahydrofuran, in mixtures of tetrahydrofuran with ether and with benzene, and with added crown ether, 18-C-6.Product distributions and stereochemistry have been examined.Dicyclohexylphosphine (DCPH) was used as a trap for intermediate free radicals to detect participation of an electron-transfer (ET) process which occurs in competition with the SN2 mechanism.The effect of the nature of the cation on the course of the reaction depends upon the medium.The effects is not usually in simple relation to the size of the cation.The SN2 mechanism competes most effectively in a good coordinating medium but is not the exclusive one with 2-bromooctane even in THF containing 18-C-6.In the poorly coordinating mixed solvents, 2-bromooctane reacts virtually exclusively by an ET process.Even the primary 1-bromooctane and 6-bromo-1-hexene show ET contributions in the mixed solvents of low cation coordinating ability.In the latter case the ET component was established both by DCPH trapping experiments and by formation of the cyclic substitution product, (cyclopentylmethyl)trimethylstannane.The mechanistic implications of these and other observations are examined.
- Alnajjar, Mikhail S.,Kuivila, Henry G.
-
p. 416 - 423
(2007/10/02)
-
- Conversion of Alcohols into Alkyl Bromides using Polymer-supported Triphenylphosphine Dibromide and Polymer-supported Triphenylphosphine and Carbon Tetrabromide
-
Alcohols were converted into alkyl bromides by reaction with polymer-supported triphenylphosphine dibromide and with polymer-supported triphenylphosphine and carbon tetrabromide.With both reagents excellent yields of bromides were obtained, but reaction with the latter reagent were faster and cleaner and in favourable cases high yields of bromide were obtained within 15 min at 20 deg C.An advantage of the polymer-supported reagents is that product isolation is facilitated by the ready separation of the supported from the non-supported species.
- Hodge, Philip,Khoshdel, Ezzatollah
-
p. 195 - 198
(2007/10/02)
-
- A NOVEL ONE STEP CONVERSION OF ALCOHOLS INTO ALKYL BROMIDES OR IODIDES
-
Alcohols are converted in high yields into alkyl bromides or iodides by a one step reaction with N,N'-carbonyldiimidazole and an excess of reactive halides such as allyl bromide or methyl iodide.KEYWORDS - alcohol; N,N'-carbonyldiimidazole; bromination; iodination; 1-alkoxycarbonylimidazole; 1-alkoxycarbonyl-3-substituted imidazolium salt; allyl bromide; methyl iodide
- Kamijo, Tetsuhide,Harada, Hiromu,Iizuka, Kinji
-
p. 4189 - 4192
(2007/10/02)
-
- Synthesis and spin trapping kinetics of new alkyl substituted cyclic nitrones
-
Three new nitrones, 5-n-propyl-5-methyl-1-pyrroline-N-oxide (PMPO), 5-n-hexyl-5-methyl-1-pyrroline-N-oxide (HMPO), and 5-n-decyl-5-methyl-1-pyrroline-N-oxide (DeMPO), amphiphilic versions of the spin trap 5,5-dimethyl-1-pyrroline-N-oxide (DMPO), have been synthesized.A comparative study of the absolute rate constants for formation and decay of the tert-butoxyl spin adducts to these cyclic nitrones as well as 3,3,5,5-tetramethyl-1-pyrroline-N-oxide (M4PO) has been undertaken using esr kinetic techniques.
- Haire, D. L.,anzen, Edward G.
-
p. 1514 - 1522
(2007/10/02)
-
- MOLECULAR MECHANISM OF HYDROGEN BROMIDE ADDITION TO OLEFINS
-
Experimental results on the products and the kinetics of the hydrogen bromide addition to alkenes-1 in non-polar solvents and on complex formation in hydrogen bromide-olefin-solvent systems are reviewed.Theoretical calculations concerning hydrogen bromide-olefin complexes are used along with the experimental evidence to suggest a molecular mechanism of addition involving intermediate cyclic structures.
- Sergeev, G. B.,Stepanov, N. F.,Leenson, I. A.,Smirnov, V. V.,Pupyshev, V. I.,et al.
-
p. 2585 - 2590
(2007/10/02)
-