Abstract 3,6-Dimethyl-1-phenyl-1H-pyrazolo[3,4-d]pyrimidin-4(5H)-one 3 was prepared by an intramolecular cyclization of N-(4-cyano-3-methyl-1-phenyl-1H-pyrazol-5-yl) acetamide 2 in ethanol in the presence of piperidine. N-allylation and N-propargyl alkylation of N-substituted pyrazolo[3,4-d] pyrimidin-4(5H)-one 3 yielded the corresponding dipolarophiles 4 and 5 which afford by condensation with arylnitrile oxides in toluene the expected new isoxazolines 6 and isoxazoles 7, respectively. On the other hand, the aminopyrazole 1 in refluxing with ethanol in the presence of sodium hydroxide afforded the corresponding carboxamide 8, which then, was converted to its ethyl 3-methyl-4-oxo-1-phenyl-4,5-dihydro-1H-pyrazolo[3,4-d] pyrimidine-6-carboxylate 9 with neat diethyl oxalate. The dipolarophile 10 on regiospecific 1,3-dipolar cycloaddition with arylnitrile oxides affords isoxazoles 11 and the unexpected deethoxycarbonylated isoxazoles 12. The target compounds were completely characterized by 1H NMR, 13C NMR, IR and HRMS.

中文翻译：

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N-取代的吡唑并[3,4-d]嘧啶-4(5H)-one衍生物通过[3+2]环加成合成新型异恶唑啉和异恶唑

摘要 3,6-二甲基-1-苯基-1H-吡唑并[3,4-d]嘧啶-4(5H)-one 3是通过N-(4-cyano-3-methyl-1-苯基-1H-吡唑-5-基）乙酰胺 2 在乙醇中在哌啶存在下。N-取代的吡唑并[3,4-d]嘧啶-4(5H)-one 3的N-烯丙基化和N-炔丙基烷基化产生相应的偶极亲和体4和5，它们通过与芳基腈氧化物在甲苯中缩合得到预期的新异恶唑啉6和异恶唑 7，分别。另一方面，氨基吡唑 1 在氢氧化钠存在下与乙醇回流，得到相应的甲酰胺 8，然后将其转化为其乙基 3-甲基-4-氧代-1-苯基-4,5-二氢- 1H-pyrazolo[3,4-d] pyrimidine-6-carboxylate 9 与纯草酸二乙酯。区域专一性 1 上的偶极体 10，