Hexamethylenetetramine Bromine Research Articles

One-Pot Synthesis of Tetracyanocyclopropane Derivatives Using Hexamethylenetetramine-Bromine (HMTAB)

Herein a direct method for synthesis of tetracyanocyclopropanes by the treatment of carbonyl compounds, malononitrile and hexamethylenetetramine-bromine (HMTAB) is described in the presence of catalytic amount of DABCO in ethanol media at room temperature.

ChemInform Abstract: Synthesis of 2‐Arylbenzimidazoles and 2‐Arylbenzothiazoles in Both Room Temperature and Microwave Condition Catalyzed by Hexamethylenetetramine—Bromine Complex.

AbstractSimilar yields are obtained at room temperature within 8h.

Synthesis of 2-arylbenzimidazoles and 2-arylbenzothiazoles in both room temperature and microwave condition catalyzed by hexamethylenetetramine–bromine complex

Abstract One-pot condensation of 2-aminothiophenol or 1,2-phenylenediamine with different aldehydes has been catalyzed by hexamethylenetetramine–bromine (HMTA-Bromine) as new, available and effective catalyst. 2-Arylbenzo-thiazoles and 2-aryl-benzimidazoles have been achieved in excellent yield and good purity.

Regioselective and High‐Yielding Bromination of Aromatic Compounds Using Hexamethylenetetramine—Bromine.

AbstractChemInform is a weekly Abstracting Service, delivering concise information at a glance that was extracted from about 200 leading journals. To access a ChemInform Abstract, please click on HTML or PDF.

Regioselective and high-yielding bromination of aromatic compounds using hexamethylenetetramine–bromine

A regioselective and highly efficient method for bromination of aromatic compounds in the presence of a stoichiometric amount of hexamethylenetetramine–bromine (HMTAB) as an efficient reagent in dichloromethane is reported. The selectivity depends on the temperature and nature of the substituent on the substrate. The reactivity of this reagent was increased by supporting it to silica gel for bromination of less activated compounds.

Efficient Hexamethylenetetramine‐Bromine (HMTAB)‐Catalyzed Synthesis of Bis(indolyl)methanes in Water.

AbstractFor Abstract see ChemInform Abstract in Full Text.

Efficient Hexamethylenetetramine‐Bromine (HMTAB)‐Catalyzed Synthesis of Bis(indolyl)methanes in Water

An efficient, facile, and environmentally friendly electrophilic substitution reaction of indoles with various aldehydes and ketones proceeded smoothly in water using the hexamethylenetetramine–bromine complex to afford the corresponding bis(indolyl)methanes in excellent yields. This method provides several advantages such as being environmentally friendly, giving high yields, and having simple workup procedure. Water was chosen as a cheap, nontoxic, green solvent.

Kinetics and mechanism of the oxidation of some α-hydroxy acids by hexamethylenetetramine-bromine

The oxidation of lactic acid, mandelic acid and ten monosubstituted mandelic acids by hexamethylenetetramine-bromine (HABR) in glacial acetic acid, leads to the formation of the corresponding oxoacid. The reaction is first order with respect to each of the hydroxy acids and HABR. It is proposed that HABR itself is the reactive oxidizing species. The oxidation of α-deuteriomandelic acid exhibits the presence of a substantial kinetic isotope effect (k H /k D = 5.91 at 298 K). The rates of oxidation of the substituted mandelic acids show excellent correlation with Brown’s σ+ values. The reaction constants are negative. The oxidation exhibits an extensive cross conjugation between the electron-donating substituent and the reaction centre in the transition state. A mechanism involving transfer of a hydride ion from the acid to the oxidant is postulated.

Kinetics and mechanism of the oxidation of substituted benzylamines by hexamethylenetetramine‐bromine

AbstractThe oxidation of substituted benzylamines by hexamethylenetetramine‐bromine (HABR) to the corresponding aldimines is first order with respect to each the amine and HABR. It is proposed that HABR itself is the reactive oxidizing species. The oxidation of deuterated benzylamine (PhCD2NH2) indicated a substantial kinetic isotope effect (kH/kD = 5.60 at 293 K). This confirmed the cleavage of an α‐C—H bond in the rate‐determining step. Correlation analyses of the rates of oxidation of 20 monosubstituted benzylamines were performed with various single‐ and multi‐parametric equations. The rates of the oxidation showed excellent correlations in terms of the Yukawa–Tsuno and Brown equations. The polar reaction constants were negative. The oxidation exhibited extensive cross‐conjugation, in the transition state, between the electron‐donating substituents and the reaction centre. A mechanism involving a hydride ion transfer from the amine to HABR, in the rate‐determining step, is proposed. Copyright © 2001 John Wiley & Sons, Ltd.

Remarkably Fast Deprotection of Semicarbazones and Tosylhydrazones Under Mild, Neutral and Solvent‐Free Conditions

AbstractRapid and selective regeneration of carbonyl compounds from their semicarbazones and tosylhydrazones was carried out using hexamethylenetetramine‐bromine (HMTAB) and N‐bromosuccinimide (NBS). Good to excellent yields, mild, neutral and solvent‐free conditions are important features of this method.

Kinetics and correlation analysis of reactivity in oxidation of organic sulfides by hexamethylenetetramine–bromine

Kinetics and correlation analysis of reactivity in oxidation of organic sulfides by hexamethylenetetramine–bromine

Kinetics and mechanism of the oxidation of lower oxyacids of phosphorus by hexamethylenetetramine bromine

The oxidation of lower oxyacids of phosphorus by hexamethylenetetramine bromine (HABR) in glacial acetic acid resulted in the formation of corresponding oxyacids with phosphorus in a higher oxidation state. The reaction exhibited 2:1 stoichiometry. The reaction is first order with respect to HABR. Michaelis–Menten-type kinetics were observed with respect to the acids. The formation constant of the phenylphosphinic acid–HABR complex also has been determined spectrophotometrically. The thermodynamic parameters for the complex formation and the activation parameters for their decomposition were calculated. The reaction showed the presence of a substantial kinetic isotope effect. It is proposed that the HABR itself is the reactive oxidizing species. It has been shown that the pentacoordinated tautomer of the phosphorus oxyacid is the reactive reductant. A suitable mechanism has been proposed. © 2000 John Wiley & Sons, Inc. Int J Chem Kinet 32: 165–170, 2000

Kinetics and mechanism of the oxidation of substituted benzaldehydes by hexamethylenetetramine-bromine

The oxidation of thirty-six monosubstituted benzaldehydes by hexa-methylenetetramine-bromine (HABR), in aqueous acetic acid solution, leads to the formation of the corresponding benzoic acids. The reaction is first order with respect to HABR. Michaelis-Menten–type kinetics were observed with respect to aldehyde. The reaction failed to induce the polymerization of acrylonitrile. There is no effect of hexamethylenetetramine on the reaction rate. The oxidation of [2H]benzaldehyde (PhCDO) indicated the presence of a substantial kinetic isotope effect. The effect of solvent composition indicated that the reaction rate increases with an increase in the polarity of the solvent. The rates of oxidation of meta- and para-substituted benzaldehydes showed excellent correlations in terms of Charton's triparametric LDR equation, whereas the oxidation of ortho-substituted benzaldehydes correlated well with tetraparametric LDRS equation. The oxidation of para-substituted benzaldehydes is more susceptible to the delocalization effect but the oxidation of ortho- and meta-substituted compounds displayed a greater dependence on the field effect. The positive value of γ suggests the presence of an electron-deficient reaction center in the rate-determining step. The reaction is subjected to steric acceleration when ortho-substituents are present. © 2000 John Wiley & Sons, Inc. Int J Chem Kinet 32: 615–622, 2000

Kinetics and Mechanism of Oxidation of Diols by Hexamethylenetetramine-bromine

The oxidation of vicinal diols by hexamethylenetetramine-bromine (HABR) proceeds by a glycol-bond fission via an intermediate complex whereas non-vicinal diols behave like monohydric alcohols towards HABR.

Kinetics and Mechanism of Oxidation of Diols by Hexamethylenetetramine–bromine

The oxidation of vicinal diols by hexamethylenetetramine–bromine (HABR) proceeds by a glycol-bond fission via an intermediate complex whereas non-vicinal diols behave like monohydric alcohols towards HABR.

Hexamethylenetetramine–Bromine: A Novel Reagent for Selective Regeneration of Carbonyl Compounds from Oximes and Tosylhydrazones†‡

Hexamethylenetetramine–bromine (HMTAB) has been found to be an efficient and selective reagent for the mild oxidative cleavage of the CN of oximes and tosylhydrazones to yield their corresponding carbonyl compounds in good to excellent yields under mild conditions.