一种关于NIH迁移的新机制。
A novel mechanism for the NIH-shift.
作者信息
Yagi H, Jerina D M, Kasperek G J, Bruice T C
出版信息
Proc Natl Acad Sci U S A. 1972 Jul;69(7):1985-6. doi: 10.1073/pnas.69.7.1985.
Kinetics of aromatization of 1,4-dimethylbenzene oxide (I) to 2,5-dimethylphenol (II) and 2,4-dimethylphenol (III), the latter arising by an NIH-Shift of a methyl group, as measured in the pH range 1-12, follow the equation -d[I]/dt = [I][k(0) + (k[unk] + k[unk])aH], where k(0) = 4.8 x 10(-3) sec(-1), k[unk] = 7.3 x 10(2) M(-1) sec(-1), and k[unk] = 5.3 x 10(2) M(-1) sec(-1). The ratio of products II to III at pH >/= 6 in the spontaneous rearrangement (k(0)) is 13 to 87, and changes to 54 to 46 in the acid-catalyzed rearrangement (k[unk] and k[unk]). While no intermediate is detectable in the acid-catalyzed rearrangement of the arene oxide by pathway k[unk], simultaneous addition of water (and other nucleophiles) by pathway k[unk] leads, via the intermediate 1,4-dimethyl-2,5-cyclohexadiene-1,4-diol (IV), to the phenols II and III. This new mechanism for the NIH-Shift serves as a model for the ease of nucleophilic addition to other arene oxides, such as those of the polycyclic aromatic hydrocarbons recently implicated in mechanisms of carcinogenesis.
在pH值1 - 12范围内测定了1,4 - 二甲基苯氧化物（I）芳香化为2,5 - 二甲基苯酚（II）和2,4 - 二甲基苯酚（III）的动力学过程，后者是通过甲基的NIH迁移产生的，其遵循方程 -d[I]/dt = [I][k(0) + (k[unk] + k[unk])aH]，其中k(0) = 4.8 x 10(-3) 秒(-1)，k[unk] = 7.3 x 10(2) M(-1) 秒(-1)，k[unk] = 5.3 x 10(2) M(-1) 秒(-1)。在自发重排（k(0)）中，pH≥6时产物II与III的比例为13比87，在酸催化重排（k[unk]和k[unk]）中变为54比46。虽然在通过途径k[unk]进行的酸催化芳烃氧化物重排中未检测到中间体，但通过途径k[unk]同时加入水（和其他亲核试剂）会经由中间体1,4 - 二甲基 - 2,5 - 环己二烯 - 1,4 - 二醇（IV）生成酚II和III。这种新的NIH迁移机制为亲核试剂加成到其他芳烃氧化物（如最近涉及致癌机制的多环芳烃的那些氧化物）的难易程度提供了一个模型。
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