OXIDATION OF PRIMARY AMINES BY DIMETHYLDIOXIRANE - AB-INITIO MODEL STUDIES

We performed ab initio studies of the initial step in dimethyldioxiran e (DMDO) oxidation of primary amines, i.e., transfer of the first oxyg en atom. The activation barrier for oxygen transfer fl om DMDO to meth ylamine 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 Angstr om and shows characteristics of being late along the reaction pathway. Polar solvents substantially decrease the reaction barrier with an ev en more remarkable decrease (to about 10% of its original value) obser ved when solvent molecules are hydrogen-bonded to the peroxy oxygens. DMDO displays characteristics of a typical electrophile in the reactio ns studied here.