Orthogonal aerobic conversion of N-benzyl amidoximes to 1,2,4-oxadiazoles or quinazolinones

Abstract

Concise synthesis of 1,2,4-oxadiazoles was achieved by heating N-benzyl amidoximes with K₃PO₄ in DMF at 60 °C under an O₂ atmosphere via benzylic C–H oxygenation. On the other hand, aerobic treatment of N-benzyl amidoximes with Cs₂CO₃ in DMSO at 100 °C could result in oxidative skeletal rearrangement to deliver quinazolinones as a major product. This orthogonal product selectivity could be realized by difference of the reaction temperature as well as selection of the solvents and inorganic bases.