Synthesis of functionalised cyclic nitrones via regioselective and unusual [3 + 2] cycloadditions of α-nitrosostyrenes with 1,3-diazabuta-1,3-dienes and imines
作者:Arun K. Sharma、Sujit N. Mazumdar、Mohinder P. Mahajan
DOI:10.1039/a702254i
日期:——
The α-nitrosostyrenes 2, generated in situ from α-halogeno oximes, undergo regioselective [3 + 2] cycloaddition with 1,3-diazabuta-1,3-dienes 1 and 5 leading to the cyclic nitrones 3 and 6, respectively. Similarly, the cyclic nitrones 12 are also formed in reactions of 2 with the trisubstituted amidines 11. Thermolysis of the nitrones 3 and 12dâf gives imidazole derivatives 13. The nitrones 6, on the other hand, on thermolysis under similar conditions, give the amidine derivatives 17. Interestingly, the treatment of both 3 and 6 with NaBH4 in methanol and the reactions of 2 with N-arylbenzamidines also yield the imidazole derivatives 13.
由 α-卤代肟原位生成的 α-亚硝基苯乙烯 2,与 1,3-diazabuta-1,3-二烯 1 和 5 进行区域选择性 [3+2] 环加成,生成环状硝酮 3 和 6,分别。类似地,环状硝酮 12 也在 2 与三取代脒 11 的反应中形成。硝酮 3 和 12d-f 的热解得到咪唑衍生物 13。另一方面,硝酮 6 在类似条件下热解,得到脒衍生物 17。有趣的是,用 NaBH4 在甲醇中处理 3 和 6,以及 2 与 N-芳基苯甲脒反应也得到咪唑衍生物 13。