Ultrasound-Promoted Radical Synthesis of 5-Methylselanyl-4,5-dihydroisoxazoles

The ultrasound-promoted synthesis of 5-methylselanyl-4,5-dihydroisoxazoles through the radical cyclization of unsaturated oximes with diaryl diselenides using Oxone (R) as an oxidant and ethanol as the solvent is described. The key step of the reaction is the ultrasound-initiated homolytic cleavage of KHSO5, leading to the formation of sulfate and hydroxyl radicals. The reactions proceed efficiently using several oximes and diselenides containing both electron-withdrawing and electron-donating groups in the aromatic ring. The positive effect of the sonication resulted in high selectivity, short reaction times (15 to 40 min) and moderate to excellent yields of the expected products (60-93 %).