Metal‐free, Phosphoric Acid‐catalyzed Regioselective 1,6‐Hydroarylation of <i>para</i>‐Quinone Methides with Indoles in Water
Biquan Xiong, Lulu Si, Yu Liu, Weifeng Xu, Tao Jiang, Fan Cao, Kewen Tang, Wai‐Yeung Wong
Abstract
An efficient, cheap and green protocol for the highly regioselective 1,6-hydroarylation of para-quinone methides (p-QMs) with indoles at the C-3 position has been established by phosphoric acid catalysis in water under transition-metal-free reaction conditions. A wide range of indole derivatives and para-quinone methides (p-QMs) are compatible for the reaction, affording the corresponding 1,6-hydroarylation products with good to excellent yields. The possible mechanism of the reaction has been explored through step-by-step control experiments. The protocol is convenient for practical applications, leading to a safe, green and feasible way for the formation of C-3 diarylmethyl functionalized indole derivatives.