Sx. Candeias et al., A practical method for the acylation of 2-imidazolidinone and 2-oxazolidinone chiral auxiliaries with 2-bromoacyl halides, SYN COMMUN, 31(21), 2001, pp. 3241-3254
Optimised conditions for the acylation of (S)-4-(1-methylethyl) -oxazolidin
-2-one 4, (R)-4-phenyloxazolidin-2-one 5 and 4-(R), (5S)-1,5-dimethyl-4-phe
nylimidazolidin-2-one 3 with 2-bromoacyl halides were developed. For imidaz
olidin-2-one 3 the optimum conditions require the use of the hindered bases
2,6-di-t-butylpyridine or 2,6-lutidine in order to reduce the ketene format
ion which has a strong preference for O-acylation.