Deuterium Isotope Effects on the Oxygen Atom Transfer Reactions of α-Azo Hydroperoxides

Article abstract of DOI:10.1021/jo00386a009

Cyclic α-azo hydroperoxide 1 (cis-3-bromo-4,5-dihydro-5-hydroperoxy-4,4-dimethyl-3,5-diphenyl-3H-pyrazole) and acyclic α-azo hydroperoxide 2 <(4-methoxyphenyl)(phenylazo)methyl hydroperoxide> were converted to the ROOD analogues 1-d and 2-d.The reactions of 1 and 1-d in CDCl3 at 34 deg C with amines, diphenyl sulfide, and 2,3-dimethyl-2-butene yielded the corresponding amine oxides, sulfoxides, and epoxides in better than 90percent yields.The reactions were found to be of the first order in both hydroperoxide and substrate (second order overall).Deuterium isotope effects (k_H/k_D) of 1.3+/-0.1 were found for the oxidation of the three types of substrate.The reactions of 2 and 2-d with benzyl methyl sulfide and 2,3-dimethyl-2-butene, carried out in C6D6 at 34 deg C, produced the corresponding sulfoxide and epoxide in 90percent+ yields.As expected, the reactions were of the second order overall (first order in hydroperoxide) in the aprotic medium.Values of k_H/k_D of 1.3+/-0.1 were found for these oxidations.The mechanistic implications of these results are discussed.