Oxidation of anilines by isoquinolinium bromochromate (IQBC) in aqueous acetic acid leads to the formation of corresponding azobenzenes. The reaction is first order with respect to both aniline and IQBC and is catalyzed by hydrogen ion. The rate of oxidation decreases with increasing dielectric constant of solvent, indicating the presence of an ion-dipole interaction. The rate of oxidation decreases with increase in concentration of KCl, possibly due to the formation of less reactive species by interaction of Cl -and protonated IQBC. The specific rate of oxidizing species anilines reaction correlates with substituents constant affording a negative reaction constant. Hammett plot is found to be valid and the correlation between enthalpies and free energies of activation is reasonably linear with an isokinetic temperature of 401 K.
Halogenation Halogenation O 0235 Pyridinium Bromochromate: A New and Efficient Reagent for Bromination of Hydroxy Aromatics. -The title compound, readily prepared from HBr, pyridine and CrO3 is described as a useful reagent for the regioselective high-yielding bromination of hydroxyarenes. -(PATWARI, S. B.; BASEER, M. A.; VIBHUTE*, Y. B.; BHUSARE, S. R.; Tetrahedron Lett. 44 (2003) 26, 4893-4894; Dep. Chem., Yeshwant Mahavidyalaya, Nanded 431 602, India; Eng.) -Mais 39-044
The copper nanoparticles grafted on carbon microsphere is employed for an efficient one-pot three-component synthesis of spirooxoindole derivatives involving isatin, malononitrile and enolizable ketones such as 3-methyl-1-phenyl-2-pyrazolin-5-one, 3-methyl-1-(2chlorophenyl)-2-pyrazoline 5-one, 4-hydroxy-6-methyl-2-pyrone and 1-methyl-4-hydroxyquinoline-2-one. The cheap starting material, easy separation, high catalytic efficiency and reusability of the catalyst for several times without loss of its efficiency, good yield of products, and simple workup are promising features of the reaction in 1:1 (v/v) aqueous-alcoholic medium.
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