A Lewis‐acid promoted chemoselective condensation of 2‐aminobenzimidazoles or 3‐aminoindazoles with 3‐ethoxycyclobutanones is presented. Diverse fused heterocycles benzo[4,5]‐imidazo[1,2‐a]pyrimidine and pyrimido[1,2‐b]‐indazole derivatives were obtained in moderate to high yields under mild conditions, the reaction mechanism of which was in sharp contrast to previous [3+3] annulation reaction of 3‐ethoxycyclobutanones.

中文翻译：

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Lewis酸促进2-氨基苯并咪唑或3-氨基吲唑与3-乙氧基环丁酮的化学选择性缩合，以构建熔融氮杂环

介绍了路易斯酸促进的2-氨基苯并咪唑或3-氨基吲唑与3-乙氧基环丁酮的化学选择性缩合。在温和条件下以中等至高收率获得了多种稠合杂环苯并[4,5]-咪唑并[1,2- a ]嘧啶和嘧啶基[1,2- b ]-吲唑衍生物与以前的3-乙氧基环丁酮的[3 + 3]环化反应形成对比。