作者:I. B. Chernikova、S. L. Khursan、L. V. Spirikhin、M. S. Yunusov
DOI:10.1007/s11172-013-0354-0
日期:2013.11
Treatment of 5-iodo-1,3,6-trimethyluracil with 50% H2SO4 gives 1,3,6-trimethyluracil; with 5-bromo-1,3,6-trimethyluracil, a mixture of 1,3,6-trimethyluracil and 6-bromomethyl-1,3-dimethyluracil is obtained. 5-Chloro-1,3,6-trimethyluracil remains inert under these conditions. According to the DFT modeling of the reactions of 5-halo-1,3,6-trimethyluracils, a nucleophilic agent can abstract either Hal+ or the methyl proton from the carbocation formed by protonation of the starting halouracil at position 5, which accounts for the formation of two products from the 5-bromo derivative. Under similar conditions, 6-methyluracil dibromohydrin yields N-bromo-5-bromo-6-hydroxymethyluracil. Bromination or chlorination of 5-hydroxymethyl- or 5-formyl-6-methyluracils follows the ipso-substitution scheme leading to 6-methyluracil 5-halo- and 5,5-dihalohydrins.
5-碘-1,3,6-三甲基尿苷在50%硫酸中处理生成1,3,6-三甲基尿苷;而在5-溴-1,3,6-三甲基尿苷中,则得到1,3,6-三甲基尿苷和6-溴甲基-1,3-二甲基尿苷的混合物。5-氯-1,3,6-三甲基尿苷在这些条件下保持惰性。根据5-卤-1,3,6-三甲基尿苷反应的DFT建模,亲核试剂可以抽象出形成于起始卤代尿苷5位质子化所产生的碳正离子中的Hal+或甲基质子,这解释了为何5-溴衍生化合物会生成两种产物。在相似条件下,6-甲基尿苷二溴醇生成N-溴-5-溴-6-羟甲基尿苷。5-羟甲基或5-醛基-6-甲基尿苷的溴化或氯化遵循邻位取代机制,生成6-甲基尿苷5-卤代物和5,5-二卤醇。