| Abstract
| - Diazetine dioxide 1a has been synthesized in a single step via oxidation of meso-2,3-diphenyl-1,2-ethanediamine with dimethyldioxirane, albeit in low yield (7%). Thermal decomposition of 1a affordedpredominantly either trans-stilbene or diphenyl glyoxime depending on solvent, temperature, and thepresence of an amine catalyst. Reaction in chloroform at 69 °C favored elimination of NO and formationof trans-stilbene. The stereospecific formation of trans-stilbene suggests a mechanism of decompositionin which C−N bond cleavage leads to a diradical intermediate stabilized by the phenyl group. Bondrotation followed by cleavage of the second C−N bond accounts for the trans-stilbene. At 25 °C inchloroform, while trans-stilbene was still the major product, some diphenyl glyoxime was also observed(4% yield). However, 1a as a solution in chloroform in the presence of Et3N, or 1a as a solution inDMSO-d6, afforded predominantly diphenyl glyoxime. These results are interpreted in terms of two closelycompeting reactions subject to the effects of entropic contributions.
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