Lai Bo-Wen, Qu Shi-Yu, Yin Yu-Xian, Li Rui, Dong Kuiyong, Shi Feng
Research Center of Chiral Functional Heterocycles, School of Chemistry and Materials Science, Jiangsu Normal University, Xuzhou 221116, China.
School of Petrochemical Engineering, Changzhou University, Changzhou 213164, China.
J Org Chem. 2024 Jul 19;89(14):10197-10211. doi: 10.1021/acs.joc.4c01080. Epub 2024 Jul 3.
A cooperative catalysis-enabled (4 + 3) cycloaddition of 2-indolylmethanols with -naphthoquinone methides (-NQMs), which were generated from enynones, has been established in the presence of silver/Brønsted acid cocatalysts. In the reaction pathway, the key -NQM intermediates were formed through Ag(I)-catalyzed cyclization of enynones, while the indole-based carbocation intermediates were generated via Brønsted acid-catalyzed dehydration of 2-indolylmethanols. By this approach, a wide range of seven-membered cyclohepta[]indoles were synthesized in good yields with high efficiency under mild reaction conditions, which serves as a useful strategy toward constructing indole-fused seven-membered rings. Moreover, the catalytic asymmetric version of this (4 + 3) cycloaddition has been realized under the cooperative catalysis of Ag(I) with chiral phosphoric acid, which offered chiral cyclohepta[]indole with a good enantioselectivity (75% ee). This work not only represents the first cooperative catalysis-enabled (4 + 3) cycloaddition of 2-indolylmethanols but also provides a good example for -NQM-involved cycloadditions, which will contribute to the chemistry of 2-indolylmethanols and enrich the research contents of cooperative catalysis.
在银/布朗斯特酸共催化剂存在下，实现了2-吲哚甲醇与由烯炔酮生成的α-萘醌甲基化物（α-NQMs）的协同催化（4 + 3）环加成反应。在反应途径中，关键的α-NQM中间体通过银（I）催化的烯炔酮环化形成，而基于吲哚的碳正离子中间体则通过布朗斯特酸催化的2-吲哚甲醇脱水生成。通过这种方法，在温和的反应条件下高效地以良好产率合成了多种七元环庚并[ ]吲哚，这是构建吲哚稠合七元环的一种有用策略。此外，在银（I）与手性磷酸的协同催化下实现了该（4 + 3）环加成反应的催化不对称版本，得到了具有良好对映选择性（75% ee）的手性环庚并[ ]吲哚。这项工作不仅代表了首例2-吲哚甲醇的协同催化（4 + 3）环加成反应，也为涉及α-NQM的环加成反应提供了一个很好的例子，这将有助于2-吲哚甲醇化学的发展并丰富协同催化的研究内容。
