Indium(III) chloride/silica gel catalyzed synthesis of pyrazolo[3,4-b]pyrrolo[3,4-d]pyridines

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• 作者：Wan-Ping Yen^a ; ^b ; Po-Lin Liu^c ; ^&dagger ; ; Naoto Uramaru^d ; Hui-Yi Lin^b ; ^{hylin@mail.cmu.edu.tw" class="auth_mail" title="E-mail the corresponding author} ; Fung Fuh Wong^b ; ^c ; ^{wongfungfuh@yahoo.com.tw" class="auth_mail" title="E-mail the corresponding author} ; ^{ffwong@mail.cmu.edu.tw" class="auth_mail" title="E-mail the corresponding author}
• 关键词：Pyrazolopyrrolopyridines ; Aza-Diels&ndash ; Alder reaction ; Pyrazoylimines ; Leaving group effect
• 刊名：Tetrahedron
• 出版年：2015
• 出版时间：18 November 2015
• 年：2015
• 卷：71
• 期：46
• 页码：8798-8803
• 全文大小：435 K

文摘

A facile synthesis of pyrazolo[3,4-b]pyrrolo[3,4-d]pyridine was developed through an Aza-Diels–Alder reaction of pyrazoylimines with maleimides in the presence of 20% wt InCl₃/silica gel in the sealed tube. Based on the metal catalyst scanning study, silica gel impregnated with indium trichloride was found to be the suitable catalyst to improve the Aza-Diels–Alder cycloaddition. In comparison with Brønsted–Lowery acetic acid condition, the Lewis acidic metal catalyst is more efficient for the Aza-Diels–Alder reaction.