Synthetic studies of the formation of oxazoles and isoxazoles from N-acetoacetyl derivatives: scope and limitations

[reaction: see text] The preparation of two types of heterocycles, oxazoles and isoxazoles, were achieved in good yields in a rapid and simple way by using N-acetoacetyl derivatives. Steric and electronic effects caused by the nature of the substituents at C1, C2, and C3 were studied. The best results were obtained with a chiral oxazolidinone moiety on C1 derived from (1R,2S)-(-)-norephedrine.