Oxidation of Primary Amines by Dimethyldioxirane: Ab Initio Model Studies

Abstract

We performed ab initio studies of the initial step in dimethyldioxirane (DMDO) oxidation of primary amines, i.e., transfer of the first oxygen atom. The activation barrier for oxygen transfer from DMDO to methylamine is 17.7 kcal/mol (in vacuum) calculated at the MP2/6-311+G** level. The reaction is exothermic: −13.0 kcal/mol (MP2/6-311+G**). The transition structure occurs at an N···O distance of 1.702 A and shows characteristics of being late along the reaction pathway. Polar solvents substantially decrease the reaction barrier with an even more remarkable decrease (to about 10% of its original value) observed when solvent molecules are hydrogen-bonded to the peroxy oxygens. DMDO displays characteristics of a typical electrophile in the reactions studied here.