Intramolecular Cyclization in 4-Azido-5-ethoxycarbonyl-2-(2′-hydroxyphenyOpyrimidine: Synthesis and Properties of 3-Ethoxy-6-(2′-hydroxyphenyl)isoxazolo[3,4-d]pyrimidine

The title azide in the solid state or in DMSO solution cyclizes thermally to isoxazolo[3,4-d]pyrimidine 2, which can either further rearrange to isoxazolone 3 or be transformed to hydroxylamine 5 or sulfoximine 7 on interaction with water or upon dilution of its DMSO solution by water, respectively; the tetrazolo tautomer 1T yields the acrylate 6.