Oxidation of Aromatic Amines with Hydrogen Peroxide Catalyzed by Cetylpyridinium Heteropolyoxometalates

Article abstract of DOI:10.1021/jo00066a012

Various substituted anilines 1 were selectively converted into the corresponsing nitrosobenzenes 2 or nitrobenzenes 3 by oxidation with aqueous hydrogen peroxide catalyzed by heteropolyoxometalates.The oxidation of anilines 1 with 35percent H2O2 catalyzed by peroxotungstophosphate (PCWP) at room temperature in chloroform under two-phase conditions afforded nitrosobenzene 2 with high selectivity.When the same reactions were carried out at higher temperature (e.g., refluxing chloroform), nitrobenzenes 3 were obtained in good yields.The oxidation of aniline (1a) with dilute H2O2 catalyzed by PCWP (2 wtpercent) in an aqueous medium produced azoxybenzene (4a) with high selectivity.Phenylazoxyalkanes 7 were prepared by the first direct cooxidation of 1a in the presence of primary aliphatic amines 6.For example, the oxidation of a 1:2 mixture of 1a and hexylamine (6b) with 35percent H2O2 (6 equiv) in the presence of PCWP produced phenylazoxyhexane (7b) along with a small amount of 4a (8percent).The reaction path for the conversion of anilines to azoxy-, nitroso-, and nitrobenzenes is described.