Completely regioselective insertion of unsymmetrical alkynes into electron-deficient alkenes for the synthesis of new pentacyclic indoles

Ke Chen, Ting Xu, Jian Liang, Meng Zhou, Jie Zhang, Wen-Juan Hao,* Jianyi Wang,* Shu-Jiang Tu, Bo Jiang*

A Lewis acid-catalyzed insertion of unsymmetrical alkynes into electron-deficient alkenes was developed for the first time, and used to produce 34 hitherto unreported pentacyclic benzo[5,6]chromeno[2,3-b]indoles with generally good yields and complete stereoselectivity. A Yb(OTf)₃-catalyzed reaction between o-alkynylnaphth-2-ols and 3-methyleneindolin-2-ones proceeded efficiently, and provided a simple and convergent protocol for alkyne difunctionalization via oxidant-free C-C double bond breaking/rearrangement. Mechanistic details of this domino process were derived by conducting systematic theoretical calculations.

Chem. Commun. 2019, 55(98), 14757-14760, DOI: 10.1039/C9CC08762A