Fernández Rosario, Ferrete Ana, Llera José M, Magriz Antonio, Martín-Zamora Eloísa, Díez Elena, Lassaletta José M
Dpto. de Química Orgánica, Universidad de Sevilla, Seville, Spain.
Chemistry. 2004 Feb 6;10(3):737-45. doi: 10.1002/chem.200305501.
The selective N-oxidation of the most nucleophilic amino nitrogen atom in hydrazides is central to the development of an unprecedented methodology for the cleavage of their N[bond]N bonds under oxidative conditions. Treatment of a series of hydrazides 1-9 with peracids such as magnesium monoperoxyphtalate hexahydrate (MMPP.6 H(2)O) or meta-chloroperbenzoic acid (m-CPBA) afforded the corresponding amides 10-16 in good-to-excellent yields (80-92 %). The extension of the methodology to carbamate-like substrates such as 17 and 18 was also investigated, but in this case the process is synthetically useless in view of the low yields observed of carbamates 19 and 20 (approximately 15 %). Experiments carried out with equivalent amounts of oxidant produced nitrones, such as 26, proceeding from the dialkylamino moiety, and (1)H NMR experiments indicated that this product is formed by fast conversion of the parent hydrazide, without detection of the expected hydrazide N-oxides. In addition, the over oxidation of 26 into nitronate 25 proceeds through an unknown intermediate. This oxidative N[bond]N bond cleavage by peracids is an alternative method for the deamination of hydrazides, and constitutes the only solution compatible with substrates carrying functionalities sensitive to reducing conditions.
酰肼中最具亲核性的氨基氮原子的选择性N-氧化是开发一种前所未有的在氧化条件下裂解其N=N键方法的核心。用诸如六水合单过氧邻苯二甲酸镁（MMPP·6H₂O）或间氯过氧苯甲酸（m-CPBA）等过酸处理一系列酰肼1-9，以良好至优异的产率（80-92%）得到相应的酰胺10-16。还研究了将该方法扩展到类似氨基甲酸酯的底物如17和18，但在这种情况下，鉴于观察到的氨基甲酸酯19和20的低产率（约15%），该过程在合成上没有用处。用等量氧化剂进行的实验产生了源自二烷基氨基部分的硝酮，如26，并且¹H NMR实验表明该产物是由母体酰肼快速转化形成的，未检测到预期的酰肼N-氧化物。此外，26过度氧化成硝酮酸盐25是通过一个未知中间体进行的。这种过酸氧化N=N键裂解是酰肼脱氨基的一种替代方法，并且是与对还原条件敏感的官能团的底物兼容的唯一解决方案。
