Brønsted-Acid-Mediated Divergent Reactions of Betti Bases with Indoles: An Approach to Chromeno[2,3-b]indoles through Intramolecular Dehydrogenative C2-Alkoxylation of Indole

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• 作者：Mohit L. Deb ; Choitanya Dev Pegu ; Bhaskar Deka ; Prantu Dutta ; Amol S. Kotmale and Pranjal K. Baruah
• 刊名：European Journal of Organic Chemistry
• 出版年：2016
• 出版时间：July 2016
• 年：2016
• 卷：2016
• 期：20
• 页码：3441-3448
• 全文大小：2133K
• ISSN：1099-0690

文摘

Divergent reactions of various 1-(aminoalkyl)naphthols and 2-(aminoalkyl)phenols (commonly known as Betti bases) with indoles under Brønsted acid catalysis is reported. With the reaction strategies, one can efficiently synthesize important indole derivatives such as 3-(α,α-diarylmethyl)indoles and chromeno[2,3-b]indoles. Furthermore, we disclose here a new C–C bond-cleavage reaction, in which naphthol and phenol behave as leaving groups to produce diarylmethanes. Inexpensive reagents such as p-toluenesulfonic acid monohydrate and molecular iodine are used to catalyze the reactions. No metal catalyst is required. The starting material of the reactions, Betti bases, are easily prepared from a three-component reaction of naphthol/phenol, aldehydes, and secondary amines. The mechanisms for the reactions are established through some control experiments. Quinone methide is the key intermediate for all the reactions reported herein.