Expedient Synthesis of Substituted Benzoheterocycles using 2-Butoxy-2,3-dihydrofurans as [4+2] Benzannulation Reagents

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• 作者：Changhui Liu ; Wenbo Huang ; Man Wang ; Bin Pan and Yanlong Gu
• 刊名：Advanced Synthesis & Catalysis
• 出版年：2016
• 出版时间：July 14, 2016
• 年：2016
• 卷：358
• 期：14
• 页码：2260-2266
• 全文大小：1638K
• ISSN：1615-4169

文摘

2-Alkoxy-2,3-dihydrofurans were found to be versatile benzannulation reagents. Indoles can be synthesized in good to excellent yields via the [4+2] annulation of 2-butoxy-2,3-dihydrofuran with pyrroles catalyzed by copper bromide. With the same protocol, carbazoles can also be obtained when indoles are used as starting material with the aid of p-toluenesulfonic acid. This type of benzannulation reagent can also be used to synthesize benzofuran, benzothiophene and naphthalene derivatives in the presence of a catalytic amount of triflic acid in moderate yields. This benzannulation protocol features wide substrate scope and mild reaction condition. Moreover, most of examples have a good regioslectivity.