p-Toluenesulfonic acid-catalyzed metal-free formal [4 + 1] heteroannulation via NH/OH/SH functionalization: One-pot access to 2-aryl/hetaryl/alkyl benzazole derivatives

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• 作者：Abhijeet Srivastava ; Gaurav Shukla ; Maya Shankar Singh ; ^{mayashankarbhu@gmail.com}
• 关键词：β-Oxodithioesters ; 2-Amino(thio)phenols ; p-Toluenesulfonic acid ; Heteroannulation ; Benzoxazoles ; Benzothiazoles ; Solventless
• 刊名：Tetrahedron
• 出版年：2017
• 出版时间：16 February 2017
• 年：2017
• 卷：73
• 期：7
• 页码：879-887
• 全文大小：979 K
• 卷排序：73

文摘

A concise and direct one-pot [4 + 1] synthetic strategy for the construction of 2-substituted benzazoles such as benzoxazoles and benzothiazoles has been disclosed in high yields (80–98%) by cascade coupling reaction of 2-amino(thio)phenols with β-oxodithioesters. The current approach enables NH/OH/SH functionalization in one-pot under solventless condition leading to diverse benzazoles without use of any external metal. A wide range of 2-amino(thio)phenols and β-oxodithioesters are compatible toward this transformation with excellent functional group tolerance. Furthermore, we preempt the wider implications of this novel strategy by demonstrating its compatibility toward versatile diversification of DNA Topoisomerase-II inhibitors.