Heteroaromatic Annulation of 2-Methyl/2-Cyanomethylbenzimidazole Dianions with <i>α</i>-Oxoketene Dithioacetals: A Highly Regioselective Synthetic Protocol for 1,2- and 2,3-Substituted/Annulated Pyrido[1,2-<i>a</i>]benzimidazoles
作者:Kausik Panda、J. R. Suresh、H. Ila、H. Junjappa
DOI:10.1021/jo026786w
日期:2003.5.1
involving [3 + 3] cyclocondensation of the dianions generated from 2-methyl (2A) and 2-cyanomethyl (3A) benzimidazoles with a variety of alpha-oxoketene dithioacetals has been reported. Thus the dianion 2A derived from 2-methylbenzimidazole has been shown to undergo regioselective 1,2-addition with various alpha-oxoketene dithioacetals derived from acyclic (4a-d) and cyclic ketones (13a,b, 20, 29 and
一系列2,3-和角1,2-取代的和成环的吡啶并[1,2-a]苯并咪唑类化合物的高效且区域选择性的环化方案,涉及由[3- + 3]生成的二价阴离子的[3 + 3]环缩合已经报道了2A)和2-氰基甲基(3A)苯并咪唑与各种α-氧杂环丁烯二硫缩醛。因此,已经证明衍生自2-甲基苯并咪唑的二价阴离子2A与衍生自无环(4a-d)和环状酮(13a,b,20、29和32)的各种α-氧杂环丁烯二硫缩醛进行区域选择性1,2-加成得到在磷酸存在下进行分子内环缩合的各种甲醇缩醛可提供相应的1-甲硫基-2,3-取代的(5a-c)和2,3-稠合的线性多环(14a,b,21、30和33)高产率的吡啶并[1,2-a]苯并咪唑。