An improved method for the synthesis of 4-substituted-3, 5-bis (methoxycarbonyl)-isoxazoline N-oxides (3) was developed by one-step cyclization of aldehydes with methyl nitroacetate in N, N-dimethylacetamide. The reaction mechanism was found to involve intramolecular nitrite ion displacement by the nitronate anion (9) ; this was confirmed by the formation of 3, 5-bis (methoxycarbonyl)-4-phenylisoxazoline N-oxide-4-d (11), starting from benzaldehyde-1-d and methyl nitroacetate. Conversion of isoxazoline N-oxides (3) to the corresponding 3, 5-bis (butylcarbamoyl) isoxazoles (7) is also discussed.
通过醛与
硝基乙酸甲酯在 N,N-二甲基乙酰胺中一步环化,开发了一种合成 4-取代-3, 5-双(甲氧基羰基)-
异恶唑啉 N-氧化物 (3) 的改进方法。发现反应机理涉及分子内
亚硝酸根离子被硝基阴离子置换 (9) ;这通过从
苯甲醛-1-d 和
硝基乙酸甲酯开始形成 3, 5-双(甲氧基羰基)-4-苯基
异恶唑啉 N-氧化物-4-d (11) 得到证实。还讨论了
异恶唑啉 N-氧化物 (3) 转化为相应的 3, 5-双(丁基
氨基甲酰基)
异恶唑 (7)。