Reaction of Oximes with Dimethyl Carbonate: A New Entry to3-Methyl-4,5-disubstit uted-4-oxazolin-2-ones

The reaction of ketone oximes with dimethyl carbonate (DMC) carried out in an autoclave at 180-190 "C and in the presence of KzCO3 yields 3-methyl-4,5-disubstituted-4-oxazolin-2-ones. The reaction can be applied to both aliphatic and aromatic ketone oximes, provided that a methylene group be present near the C-N bond. Nonoptimized yields range from 22 to 48 % . The reaction seems to be a [3,3] sigmatropic rearrangement where DMC plays a key role in causing the initial N-methylation of the oximes.