Tandem [8 + 2] Cycloaddition−[2 + 6 + 2] Dehydrogenation Reactions Involving Imidazo[1,2-<i>a</i>]pyridines and Imidazo[1,2-<i>a</i>]pyrimidines
作者:Maialen Aginagalde、Yosu Vara、Ana Arrieta、Ronen Zangi、Vicente L. Cebolla、Arantzazu Delgado-Camón、Fernando P. Cossío
DOI:10.1021/jo9022815
日期:2010.5.7
The reaction between benzynes and imidazo[1,2-a]pyridines (pyrimidines) to form benzo[a]imidazo[5,1,2-cd]indolizines and 2,3,9c-triazocyclopenta[j,k]fluorenes has been studied computationally and experimentally. It is found that these reactions take place via tandem [π8s + π2s] and [σ2s + π6s + σ2s] processes. The [8 + 2] cycloaddition steps are essentially barrierless, and the aromatization steps
苯并炔与咪唑并[1,2- a ]吡啶(嘧啶)之间形成苯并[ a ]咪唑并[5,1,2- cd ]吲哚并2,3,9c-三偶氮环戊[ j,k ]芴的反应通过计算和实验研究。据发现,这些反应通过串联发生[ π 8个小号+ π 2小号]和[ σ 2小号+ π 6小号+ σ 2个小号]流程。[8 + 2]环加成步骤基本无障碍,芳构化步骤通过高度同步的芳族过渡结构进行。从实验的角度来看,该反应在微波辐射下并且使用2-(三甲基甲硅烷基)苯基三氟甲磺酸酯作为苯炔前体是可行的。根据起始三氟甲磺酸酯的取代方式,可以实现反应的完全区域控制。如此制备的四环化合物在365 nm激发时发出蓝光,并表现出令人感兴趣的光物理性质。