2-Indolymethanols as 4-atom-synthons in oxa-Michael reaction cascade: access to tetracyclic indoles
Tian-Jiao Han1, Min-Can Wang1, Guang-Jian Mei1
1Green Catalysis Center, and College of Chemistry, Zhengzhou University, Zhengzhou 450001, China. wangmincan@zzu.edu.cn.
Abstract:
The first Brønsted acid-catalyzed oxa-Michael reaction cascade of 2-indolylmethanols with trione alkenes was accomplished. By using this practical approach, a variety of tetracyclic indoles were readily created in an ordered sequence with excellent regio- and diastereoselectivity. 2-Indolylmethanols commendably served as four-atom synthons, as opposed to the common three-atom synthons in the previous literature reports. The regioselectivity issue was well handled by the employment of a strong Brønsted acid catalyst. In addition, its dual role in activation of substrates via hydrogen-bonding interaction and acceleration of subsequent intramolecular cyclization and dehydration was proposed to account for the high reaction efficiency.
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