Pyridinium hydrobromide perbromide, oxidation

D KIE of 6.35 has been observed in the oxidation of a-deuteriomandelic acid by pyri-dinium bromochromate to the corresponding oxo acid. The analysis of the D KIE indicated that the reaction involves a symmetric transition state443. The oxidations of phosphinic and phosphorous acids by pyridinium bromochromate exhibits a substantial primary deuterium KIE444. The hydroxyacids, glycolic, lactic, mandelic and malic acids are oxidized by pyridinium hydrobromide perbromide in acetic acid-water mixtures to oxo acids445. The primary KIE in the oxidation of a-deuteriomandelic acid is kn/kn = 5.07, and it does not exhibit a solvent isotope effect. A mechanism involving hydride ion transfer to the oxidant has been proposed445. 

The oxidation of substituted benzylamines by pyridinium hydrobromide perbromide is of first order with respect to both the oxidant and the amine. The oxidation of deuter-ated benzylamine exhibited a kinetic isotope effect (kH/kD = 3.20 at 303 K.). The rates showed excellent correlations in terms of Taft s and Charton s multiparametric equations. A mechanism has been proposed.135... 

Oxidation of the 4a/7-pyrido[2,l-/][l,2,4]triazine (76) with bromine was reported <77LA1718>. The fully conjugated tribromide (77) underwent ring contraction with water to give (78) (Scheme 2). Bromination of the mesoionic (79) with pyridinium hydrobromide perbromide gave 8-mono and 8,10-dibromo derivatives. Compound (79) with DMAD afforded the tetracyclic 1 1 adduct (80) (Equation (6)) <83JCS(P1)349>. 

Methods for the regeneration of ketones from dithioacetals continue to be developed, including the use of ceric ammonium nitrate (four equivalents are necessary), ° sulphuryl chloride fluoride, trimethyloxonium tetrafluorobor-ate, ° mercuric oxide and tetrafluoroboric acid, and pyridinium hydrobromide perbromide under phase-transfer conditions. ... 

Related Reagents. Bromine-r-Butylamine Bromine Chloride Bromine-l,4-Diazabicyclo[2.2.2]octane Bromine-1,4-Dioxane Bromine-Silver(I) Oxide Bromine-Triphenyl Phosphite iV-Bromosuccinimide A7-Bromosiiccinimide-Dimethylformamide 7V-Bromosuccinimide-Dimethyl Sulfide Al-Bromosuccinimide-Sodium Azide Copper(II) Bromide Hy-drobromic Acid Mercury(II) Oxide-Bromine Phosphoms(III) Bromide Pyridinium Hydrobromide Perbromide Sodium Bromide Thallium(III) Acetate-Bromine. 

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