Studies on Heteropentalenes. V. Cycloadditions of 5-Aryl-3-methylimidazo[5,1-<i>b</i>]thiazoles with Acetylenic Esters Leading to 5-Aryl-3-methylthiazolo[2,3-<i>c</i>]benzimidazoles and Related Heterocycles
作者:Noritaka Abe、Tarozaemon Nishiwaki、Kotaro Ikeda
DOI:10.1246/bcsj.55.2464
日期:1982.8
Cycloaddition of 5-aryl-3-methylimidazo[5,1-b]thiazoles with dialkyl acetylenedicarboxylate in an aprotic nonpolar solvent gives a number of products including epimeric thiazolo[2,3-c]benzimidazoles (3 and 4) [1:2-cycloadducts], epimeric 5,10b-ethenothiazolo[3′,2′:3,4]imidazo[1,5-a]-pyridines (5 and 6) [1:3-cycloadducts], and thiazolo[3′,2′:3,4]imidazo[1,2-a]pyridines [1:3-adducts]. At higher temperature
在非质子非极性溶剂中,5-芳基-3-甲基咪唑并[5,1-b]噻唑与乙炔二羧酸二烷基酯的环加成得到许多产物,包括差向异构噻唑并[2,3-c]苯并咪唑(3和4)[1:2 -环加合物]、差向异构 5,10b-乙烯噻唑并[3',2':3,4]咪唑并[1,5-a]-吡啶(5和6)[1:3-环加合物]和噻唑并[3', 2':3,4]咪唑并[1,2-a]吡啶[1:3-加合物]。在较高温度下,1:2-环加合物的形成优于 1:3-加合物,而后者在室温下占主导地位。在非质子极性介质中,基本上产生了 1:3-环加合物(5 和 6)和 6-芳基吡啶-2,3,4,5-四羧酸四烷基酯。已发现 3 和 4 的差向异构化与断裂成 4H-1,4-苯并噻嗪有很好的竞争。