MCPBA= m-chloroperbenzoic acid. bIsolated yield. Starting material. drt= room temperature.'N-Oxide should be produced but in IC (6 3.32). The 'H NMR spectrum of 5c exhibited signals for four methylene protons of the piperazine moiety as doublets at 3.59 ppm (2 H) and 3.86 ppm (2 H) and as triplets at 4.03 ppm (2 H) and 4.23 ppm (2 H). The mass it could not be isolated. terized by 'H NMR analysis and mass spectrometry (Table ...