Synthesis of dihydrocarbazoles via (4+2) annulation of donor-acceptor cyclopropanes to indoles

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• 作者：Changhui Liu^a ; Li Zhou^a ; Wenbo Huang^a ; Man Wang^a ; Yanlong Gu^a ; ^b ; ^{klgyl@hust.edu.cn" class="auth_mail" title="E-mail the corresponding author}
• 关键词：Dihydrocarbazoles ; Cyclopropanes ; Acid catalysis ; Ring-opening reactions
• 刊名：Tetrahedron
• 出版年：2016
• 出版时间：28 January 2016
• 年：2016
• 卷：72
• 期：4
• 页码：563-570
• 全文大小：640 K

文摘

Dihydrocarbazoles were synthesized through a novel [4+2] annulation of donor-acceptor cyclopropanes (DACs) to indoles. This reaction was performed in ethanol by using para-toluenesulfonic acid as catalyst. Mechanism of this reaction might involve the following three steps: (i) an electrophilic ring-opening reaction of the DACs with indoles, in which C3 position of indole acts as a nucleophilic site, (ii) an intramolecular dehydration induced ring-closing reaction occurs that offers a spiro intermediate, and (iii) a following 1,2-migration which leading to a dihydrocarbazole scaffold. Otherwise, dihydroisoindole can also be constructed by replacing the indole component with pyrrole as nucleophile.