We report that structurally complex guanidinium heterocycles can be prepared in one step by regio- and stereoselective [4 + 2]-cycloadditions of N-amidinyliminium ions with indoles or benzothiophene. In contrast to reactions of these heterodienes with alkenes, density functional theory (DFT) calculations show that these cycloadditions take place in a concerted asynchronous fashion. The [4 + 2]-cycloaddition of N-amidinyliminium ions (1,3-diaza-1,3-dienes) with indoles and benzothiophene are distinctive, as related [4 + 2]-cycloadditions of N-acyliminium ions (1-oxa-3-aza-1,3-dienes) are apparently unknown.

中文翻译：

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N-脒基亚胺离子与吲哚环加成构建饱和胍杂环

我们报告说，结构复杂的胍杂环可以通过N-脒基亚胺离子与吲哚或苯并噻吩的区域和立体选择性 [4 + 2]-环加成反应一步制备。与这些异二烯与烯烃的反应相反，密度泛函理论 (DFT) 计算表明，这些环加成以协调的异步方式发生。在[4 + 2] -环的Ñ -amidinyliminium离子（1,3-二氮杂-1,3-二烯）与吲哚和苯并噻吩是独特的，作为与[4 + 2]的-cycloadditions N- acyliminium离子（1- oxa-3-aza-1,3-diene）显然是未知的。