Tetrabutylammonium tribromid

In general, it is difficult to carry out a step-by-step bromination of phenols with bromine, since phenols react very rapidly with bromine, which leads to the polybromo-substituted phenols. We found that the reaction of phenols with calculated amounts of tetrabutylammonium tribromide (TBA Br3) or BTMA Br3 in... 

Berthelot et al. have already reported that the reaction of aromatic amines with tetrabutylammonium tribromide (TBA Br3) in chloroform gave p-selective bromo-substituted aromatic amines (ref. 10). We also carried out the bromination of... 

Both the CTC and the bromonium tribromide species have their A-max at 272 nm, but with very different e. Furthermore, at the employed Br2 concentrations the counteranion of the bromonium ion is partitioned between Br3 and Br5 , the latter having its A-max batochromically shifted at 310 nm. The equilibrium constant between the tribromide and the pentabromide species of Scheme 4 is 22.3 M l, that is nearly coincident with that found for the tetrabutylammonium tribromide-pentabromide equilibrium (ref. 22). 

Monobromination (para) of aromatic amines has been achieved with tetrabutylammonium tribromide Berthelot, J. Guette, C. Desbene, P. Basselier, J. Chaquin, R Masure, D. Can. J. Chem., 1989, 67, 2061. For another procedure, see Onaka, M. Izumi, Y. Chem. Lett., 1984, 2007. 

Tetrabutylammonium tribromide, Bu4N+Br3 (1), m.p. 84°. Supplier Janssen Chimica. 

Phenyl azide-Aluminum chloride, 240 Haloboration Boron tribromide, 43 Halogenation Boron tribromide, 43 Tetrabutylammonium tribromide, 287 Hydroacylation Dicarbonyl(nitrosyl)triphenyl-phosphinecobalt, 101 Hydrofluorination... 

Dimethyl tartrate, 124 of arenes Bromine, 170 of other substrates N-Bromosuccinimide, 49 Dimethyl tartrate, 124 Tetrabutylammonium tribromide, 287... 

Another approach in the study of the mechanism and synthetic applications of bromination of alkenes and alkynes involves the use of crystalline bromine-amine complexes such as pyridine hydrobromide perbromide (PyHBts), pyridine dibromide (PyBn), and tetrabutylammonium tribromide (BiMNBn) which show stereochemical differences and improved selectivities for addition to alkenes and alkynes compared to Bn itself.81 The improved selectivity of bromination by PyHBn forms the basis for a synthetically useful procedure for selective monoprotection of the higher alkylated double bond in dienes by bromination (Scheme 42).80 The less-alkylated double bonds in dienes can be selectively monoprotected by tetrabromination followed by monodeprotection at the higher alkylated double bond by controlled-potential electrolysis (the reduction potential of vicinal dibromides is shifted to more anodic values with increasing alkylation Scheme 42).80 The question of which diastereotopic face in chiral allylic alcohols reacts with bromine has been probed by Midland and Halterman as part of a stereoselective synthesis of bromo epoxides (Scheme 43).82... 

The reaction between selenium(IV) and tetrabutylammonium tribromide is postulated to involve a direct two-electron transfer as the test for the formation of free radical was negative. The proposed active reacting species are tribromide ion and HSe03 ion.165... 

Oxidation of thio acids by tetrabutylammonium tribromide showed Michaelis-Menten-type kinetics with respect to the thio acid. The effect of solvent composition was analysed using the Grunwald-Winstein equation. A mechanism involving the formation of an intermediate complex in the pre-equilibrium and its subsequent decomposition in a slow step is proposed.129... 

Butylcalix[n]arenes can be converted into monospirodienones 43 by mild oxidation (tetrabutylammonium tribromide) under alkaline conditions.89 The structure of two examples 43a,b has been established by single-crystal X-ray analysis.90 Their chirality is mainly due to the asymmetrically substituted spiro carbon atom, however, compound 43a has also some similarity with calix[4]arenes having three different phenolic units in the order AABC (see below). Under neutral conditions the oxidation of r-butylcalix[4]arene leads to the formation of 44 which has been also confirmed by single-crystal X-ray analysis.91... 

H0(CH2)20H, Tetrabutylammonium tribromide, triethylorthoformate, 21-97% yield. This method produces HBr in situ and can be use to prepare both cyclic and acyclic acetals." ... 

HS(CH2) SH, neat, Me2S-Br2, 65-98% yield. HBr, probably generated in situ by oxidation of the dithiol, is probably the true catalyst in this reaction. Aldehydes react selectively in the presence of ketones. This catalyst has also been used to prepare 1,3-dioxolanes. Tetrabutylammonium tribromide similarly serves as a catalyst. ... 

The addition of bromine to C —C triple bonds with tetrabutylammonium tribromide gives the ( )-dibromoalkene stereoselectively 14°. 

Bromination also can be carried out with reagents that supply bromine in the form of the Br anion. One such reagent is pyridinium bromide tribromide. Another is tetrabutylammonium tribromide. These reagents are believed to react via the Brj-alkene complex and have a strong preference for anti addition. 

E-l,2-dibromoalkenes has been demonstrated using tetrabutylammonium tribromide, the high product stereoselectivity being rationalized by... 

With tetrabutylammonium tribromide, the reaction was second order, first order in [cyclohexene] and first order in Bra". 

The tetrabutylammonium tribromide (TBATB) oxidation of p-substituted acetophenones to a-bromoacetophenone in ACOH-H2O (50% vol/vol) was first order in TBATB and the rate increased with the substrate concentration. The reactive TBATB species was Br3 ion, and its electrophilic attack on acetophenone gave a transition state which decomposed in the rate-determining step. °... 

A related system for the bromination of alkenes and alkynes using NaOCl, sodium bromide and a phase transfer agent such as tetra-butylammonium hydrogen sulfate has been reported [28]. In this reaction a third, red coloured phase formed between the aqueous and organic layers, which consisted mainly of tetrabutylammonium tribromide. This brominating system converted cyclohexene to 1,2-dibromocyclohexane (40%) and l-bromo-2-chlorocyclohexane (46%), 1-octyne to 1-bromo-l-octene (88%) and diphenylmethane to benzophenone (65%). 

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