Synthesis of 1,3-diaryl-1H-benzo[g]indazoles

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• 作者：Meng-Yang Chang ; Hang-Yi Tai ; Yeh-Long Chen ; Ru-Ting Hsu
• 关键词：1H-Benzo[g]indazoles ; Aldol condensation ; Knorr pyrazole synthesis ; One-pot combination ; Oxidative cleavage annulation
• 刊名：Tetrahedron
• 出版年：2012
• 出版时间：23 September, 2012
• 年：2012
• 卷：68
• 期：38
• 页码：7941-7948
• 全文大小：1537 K

文摘

A facile three-step synthetic route toward 1,3-diaryl-1H-benzo[g]indazoles 1a-1n starting with 3,4-dimethoxy-2-allylbenzaldehyde (6) in modest total yield is described. The facile route was carried by aldol condensation of aldehyde 6 with aryl methyl ketones 5a-5d in alkaline MeOH at reflux, Knorr pyrazole synthesis of the resulting chalcones 4a-4d with aryl hydrazines 3a-3e in EtOH at reflux followed by DDQ-mediated aromatization in toluene at reflux, and oxidative cleavage annulation of olefins 2a-2n with the one-pot combination of OsO₄/NaIO₄/HOAc in the aqueous THF at reflux.