The Mechanism of Oxygen Transfer from an Oxaziridine to a Sulfide and a Sulfoxide: A Theoretical Study

Chiral oxaziridines provide synthetically useful reagents for the asymmetric transfer of an oxygen atom to a variety of substrates. One of the fundamental questions pertaining to the approach of the reactants is whether either of the lone pairs on the electrophilic oxygen exerts a significant electronic influence on the transition structure. Employing a model reaction system, we have found that oxygen atom transfer from an oxaziridine to a sulfoxide is essentially invarient to the torsional orientation of the two fragments in the transition state. The planar and spiro transition structures differ in energy by only 0.4 kcal/mol at the MP4SDTQ/4-31G(d) level of calculation. These data are consistent with experimental observations and with the earlier ab initio calculations on this type of oxygen atom transfer.