ZnBr2-Mediated Cascade Reaction of o-Alkoxy Alkynols: Synthesis of Indeno[1,2-c]chromenes

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• 作者：Amol Milind Garkhedkar ; Gopal Chandru SenadiJeh-Jeng Wang
• 刊名：Organic Letters
• 出版年：2017
• 出版时间：February 3, 2017
• 年：2017
• 卷：19
• 期：3
• 页码：488-491
• 全文大小：442K
• ISSN：1523-7052

文摘

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.