Imines and derivatives. Part 24. Nitrone synthesis by imine oxidation using either a peroxyacid or dimethyldioxirane

The oxidation of N-alkyl imines by m-chloroperoxybenzoic acid to yield nitrones was facilitated by (i) the presence of C-aryl substituents, (ii) steric inhibition of attack at the imino C-atom, (iii) electron donating para-substituents on the C-aryl substituent, (iv) non-hydroxylic solvents, (v) optimal conjugation between C-aryl substituents and the imino group, and (vi) less bulky N-alkyl groups.The oxidation of N-alkyl imines by dimethyldioxirane (DMD) in dichloromethane–acetone solution yielded nitrones without evidence of oxaziridine formation. The yields of isolated nitrones were higher for C,C-diaryl imines and for imines bearing less bulky N-alkyl substituents. N–H substituted ketimines were found to yield oximes after reaction with dimethyldioxirane.