29974-68-3Relevant articles and documents
Linear Paired Electrolysis—Realising 200 % Current Efficiency for Stoichiometric Transformations—The Electrochemical Bromination of Alkenes
Strehl, Julia,Abraham, Marvin L.,Hilt, Gerhard
supporting information, p. 9996 - 10000 (2021/03/31)
The generation of bromine by oxidation of bromide anions at the anode and reduction of molecular oxygen at the cathode to hydrogen peroxide resulted in the overall formation of two molecules of Br2 (=four electron oxidation) by passing just two electrons through the solution. The bromine was used for the bromination of alkenes and thereby a linear paired electrolysis was attained which resulted in current efficencies of up to 200 %. Also, the diiodination of cyclohexene as well as the electrophilic aromatic bromination of an electron-rich arene were realised both in 168 % current efficiencies.
A Highly Efficient Method for the Bromination of Alkenes, Alkynes and Ketones Using Dimethyl Sulfoxide and Oxalyl Bromide
Ding, Rui,Li, Jiaqi,Jiao, Wenyi,Han, Mengru,Liu, Yongguo,Tian, Hongyu,Sun, Baoguo
, p. 4325 - 4335 (2018/11/21)
The pairing of DMSO and oxalyl bromide is reported as a highly efficient brominating reagent for various alkenes, alkynes and ketones. This bromination approach demonstrates remarkable advantages, such as mild conditions, low cost, short reaction times, provides excellent yields in most cases and represents a very attractive alternative for the preparation of dibromides and α-bromoketones.
Facile one-pot synthesis of α-bromoketones from olefins using bromide/bromate couple as a nonhazardous brominating agent
Patil, Rajendra D.,Joshi, Girdhar,Adimurthy, Subbarayappa,Ranu, Brindaban C.
experimental part, p. 2529 - 2532 (2009/09/06)
A new method for the preparation of α-bromoketones from olefins using bromide/bromate couple as a nonhazardous brominating agent has been developed. Several α-bromoketones were successfully prepared from a variety of olefins by this method. This procedure is an alternative to conventional molecular bromine.
Phase-vanishing reactions that use fluorous media as a phase screen. Facile, controlled bromination of alkenes by dibromine and dealkylation of aromatic ethers by boron tribromide
Ryu, Ilhyong,Matsubara, Hiroshi,Yasuda, Shinji,Nakamura, Hiroyuki,Curran, Dennis P.
, p. 12946 - 12947 (2007/10/03)
In fluorous triphasic reactions, such as bromination of alkenes by dibromine and dealkylation of aromatic ethers by boron tribromide, the middle fluorous phase acts as a liquid membrane permitting passive transport of the reagents at the bottom to the top layer involving the substrates, thereby regulating the reactions. Copyright
Debrominations of vic-Dibromides with Diorganotellurides. 1. Stereoselectivity, Relative Rates, and Mechanistic Implications
Butcher, Timothy S.,Zhou, Feng,Detty, Michael R.
, p. 169 - 176 (2007/10/03)
Debrominations of vic-dibromides with diaryl tellurides 1-4 and di-n-hexyl telluride (9) are described. A mechanistic explanation of the debromination is offered which accounts for several key experimental observations: (1) the reaction is highly stereoselective with erythro-dibromides giving trans-olefins and threo-dibromides giving cis-olefins, (2) the reaction is accelerated by more electron-rich diorganotellurides, (3) the reaction is accelerated in a more polar solvent, (4) the reaction is accelerated by the addition of carbocation-stabilizing substituents to the carbons bearing the bromo substituents, and (5) erythro-dibromides are much more reactive than threo-dibromides. It is proposed that bromonium ion formation from the vic-dibromide is slow and rate-determining. Bromonium ion formation is followed by rapid scavenging of "Br-" by the diorganotelluride. The bromonium ion formation provides stereoselectivity and eclipsing interactions lower the reactivity of threo-dibromides. No intermediate species were observed by 1H NMR.
Bromination of Alkenes in Acetonitrile. A Rate and Product Study
Bellucci, Giuseppe,Bianchini, Roberto,Chiappe, Cinzia
, p. 3067 - 3073 (2007/10/02)
The reaction of simple alkenes and aryl alkenes with molecular bromine in damp MeCN occurred with solvent incorporation to give 2-bromo-1-(N-acetylamino)alkanes, 2-methyloxazolines, 2-acetoxyalkylamine hydrobromides, and 2-(N-acetylamino) alcohols.These products arose by the transformation of initially formed 2-bromo-1-(N-acetylamino)alkanes obtained by MeCN attack on bromonium or bromocarbonium ions to give nitrilium tribromide salts.These reacted with water to give 2-bromo-1-(N-acetylamino)alkanes.The kinetic profile of the reaction showed a very fast initial reaction of the alkene and Br2 to yield the nitrilium tribromide, followed by a much slower reaction of Br3(1-) with the alkene.The incorporation of MeCN was Markovnikov and stereospecifically anti.The degree to which incorporation of solvent occurred depended upon the alkene structure and the initial reagent concentrations.A rationalization for the observed chemoselectivity and its dependence on the reaction conditions is offered.
Homolytic Ring Fission reactions of Bicycloalkanes and Bicycloalk-2-yl Radicals: Electron Spin Resonance Study of Cycloalkenylmethyl Radicals
Roberts, Charles,Walton, John C.
, p. 879 - 886 (2007/10/02)
Hydrogen abstraction from bicycloalkanes (n=3-6) by t-butoxyl radicals was examined by an e.s.r. technique.The main site of attack was C(2) giving bicycloalk-2-yl radicals which rearranged by β-scission of the outer cyclopropane bonds to give cycloalkenylmethyl radicals.This is in contrast to the bicycloalk-2-yl radicals (n=1,2) which rearranged by fission of the inter-ring bonds to give cycloalkenyl radicals. β-Scission in bicycloalk-2-yl radicals was examined by semi-empirical SCF MO calculations.The conformations and barriers to internal rotation of the cycloalkenylmethyl radicals were determined from the variation in the β-H hyperfine splitting constants with temperature.Photobromination of bicycloalkanes (n=3,4) was also investigated in CCl4 solution.The main process was bimolecular homolytic substitution (SH2) by bromine atoms at the cyclopropane carbons, but there was an increase in hydrogen abstraction with ring size.The SH2 reactions parallel the β-scission reactions of the bicycloalk-2-yl radicals in that the main bond undergoing fission changes from the inter-ring bond to the outer cyclopropane bond as the ring size increases.
OXIDATION OF N-ALKYL-N'-TOSYLHYDRAZINES WITH BROMINE
Palmieri, Gianni
, p. 4097 - 4102 (2007/10/02)
Oxidation of N-alkyl-N'-tosylhydrazines with bromine yield alkyl bromides, vicinal alkyl dibromides and traces of alcohols.The main products of primary hydrazines are monobromides whereas secondary hydrazines preferably produce dibromides.The reaction proceeds with evolution of nitrogen and hydrobromic acid and by the formation of intermediate sulfinic ester wich may be isolated.Various substrates were examined under different conditions to confirm the validity of the reaction mechanism hypothesized.
One-pot Conversions of Amines into Olefins via Non-isolated Pyridinium Intermediates
Katritzky, Alan R.,Lloyd, Jeremy M.
, p. 2347 - 2352 (2007/10/02)
Secondary alkyl primary amines are converted by the pyrylium salt (1) directly at 20 deg C into olefins via the corresponding secondary carbenium ions.Isomeric olefin mixtures are elucidated and result from carbenium ion rearrangements.
The Effect of Electrochemically Generated Positive Bromine Species in Acetonitrile on the Cleavage of C-Br and C-Cl Bonds.
Becker, James Y.,Zemach, Dvora
, p. 336 - 340 (2007/10/02)
The fate of bromine formed from C-Br cleavage during the course of anodic oxidation of alkyl bromides in acetonitrile on platinum has been investigated potentiostatically.It is suggested that positive bromine species are formed and they are potentially reactive towards alkyl bromides, yielding similar products to those obtained by direct anodic oxidation of the same bromides.Furthermore, whereas alkyl chlorides do not undergo C-Cl fission by direct anodic oxidation it is shown that positive bromine species are energetically sufficient to break C-Cl bonds, although not very efficiently.We suggest that a possible structure for the complex between acetonitrile and positive bromine species is mainly +Br3- and the mechanism for its formation is discussed.The spectrum of this species found identical to that of Br3- (269 nm) in acetonitrile.
