SYNTHESIS AND REARRANGEMENT OF 2-OXO-3-PHENYLISOXAZOLO[2,3-A]PYRIMIDINES

2-Oxo-3-phenylisoxazolo[2,3-alpha]pyrimidine derivatives were synthesi zed by the reaction of 3-amino-4-phenyl-5-isoxazolone with malonaldehy de tetraacetal, 3-oxobutyraldehyde diacetal, 2,4-pentanedione, and 1-p henyl-1,3-butanedione. The regioselectivity of this reaction was deter mined by X-ray single crystal structural analysis. Upon heating either in water or in ethanol this bicyclic system underwent a ring opening, followed by decarboxylation to yield phenylpyrimidylmethanol and phen ylpyrimidyl methyl ethers. The structures of these 2-oxoisoxazolo[2,3- alpha]pyrimidines and the mechanism of their rearrangement is discusse d.