Reaction of Oximes with Dimethyl Carbonate: A New Entry to 3-Methyl-4,5-disubstituted-4-oxazolin-2-ones
The reaction of ketone oximes with dimethyl carbonate (DMC) carried out in an autoclave at 180-190 deg C and in the presence of K2CO3 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 48percent.The reaction seems to be a sigmatropic rearrangement where DMC plays a key role in causing the initial N-methylation of the oximes.
Marques, C. A.,Selva, M.,Tundo, P.,Montanari, F.
p. 5765 - 5770
(2007/10/02)
STEREOSELECTIVE SYNTHESIS OF (+/-)-CONHYDRINE, (+/-)-EPHEDRINE, AND (+/-)-METHYLEPHEDRINE
(+/-)-Conhydrine, (+/-)-ephedrine, and (+/-)-N-methylephedrine have been synthesized with a complete stereochemical control by utilizing carbanions in which the negative charge is located at the position α to the nitrogen atom of N-acylamines.