A Lewis acid-mediated cascade annulation of o-alkoxy alkynols in the presence of ZnBr₂ has been developed. The cascade cyclization proceeds through a 5-exo-dig cyclization followed by a Friedel–Crafts reaction and ring-opening sequence to synthesize indeno[1,2-c]chromenes. This protocol provides a broad substrate scope in moderate to good yields with high regioselectivity. The reaction with benzo-fused cycloalkyl ketones gave an unexpected alkyne C–C bond cleavage resulting in fused polycycles.

中文翻译：

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ZnBr ₂介导的邻烷氧基炔醇的级联反应：茚并[1,2- c ]二甲基苯的合成

已经开发了在ZnBr ₂存在下路易斯酸介导的邻烷氧基炔醇的级联环化反应。级联环化是通过5- exo- dig环化进行的，然后进行Friedel-Crafts反应和开环序列以合成茚并[1,2- c ]色烯。该方案以中等至良好的产率和高的区域选择性提供了广泛的底物范围。与苯并稠合的环烷基酮的反应产生了意外的炔烃C–C键断裂，从而导致了稠合的多环。