Nitration of Bio-related Compounds with Peroxynitrite Mechanistic Implications to Biological Nitration

为了深入了解生物硝化的机理，研究了过氧亚硝酸根与一些生物相关模型化合物在缓冲水溶液和乙腈中的反应。所用化合物包括酚类、N，N-二甲基苯胺和活性烯烃，如二苯乙烯、1，4-二苯基丁二烯和1，4-二苯基丁烯。在碱性水溶液中，叠氮化钠被臭氧氧化生成过氧亚硝酸根，在苯酚的作用下，芳香环上同时发生硝化和羟基化反应，产物分布呈现典型的亲电性。副产品包括苯二酮和环己二烯。A^A^-二甲基苯胺发生了广泛的脱甲基化反应，表明亚硝酸根离子是活性物种。二苯乙烯得到苯甲醛、二苯乙烯环氧化物和苯甲醛，以及一些环硝化产物。氧化断裂碳-碳键的机理目前尚不清楚，因为氧化二苯乙烯、1，2-二苯基乙醇和二苯基-甲氧基乙酮对过氧亚硝酸根都是惰性的。在相似的条件下，二苯乙酰与环硝化产物一起以苯并苯为主要产物；奇怪的是，其取代方式只有邻位和间位。烯键比乙酰键活性更强，但亲电过程的差异并不像预期的那么大。烯键和多烯键之间的相对反应性差异也不是很大。

In order to get insight into the mechanism of biological nitration, the reaction of peroxynitrite with some bio-related model compounds has been investigated in buffered aqueous solutions and acetonitrile. The compounds employed included phenols, N, N- i dimethylanline and activated olefines such as stilbene, 1, 4-diphenylbutadiene and 1, 4- diphenylbutenyne. Peroxynitrite was generated by the oxidation of sodium azide with ozone in aqueous alkaline solution.With phenols, concurrent nitration and hydroxylation took place on aromatic ring and the product distribution pattern showed a typical electrophilic nature. Side products included quinones and cyclohexadienes. A^A^-Dimethylaniline underwent extensive demethylation, which suggested involvement of the nitrosonium ion as active species. Stilbene afforded benzil, stilbene epoxide and benzaldehyde, together with some ring nitration products. The mechanism of oxidative cleavage of the carbon-carbon bond is not clear at present, since stilbene oxide, 1, 2-diphenylethanediol and diphenylhy＆roxyethanone were all found to be inert toward peroxynitrite. Under similar conditions, diphenylacetyle afforded benzil as the main product along with ring nitration products ; strangely enough, the substitution pattern of which was only ortho and meta. The olefinic bond was more reactive than the acetylenic one, but the difference was not so large as expected from the electrophilic process. The difference in relative reactivity between the olefinic and polyenic bonds was not so large, either.