Recent Advances on Regioselective C-H Borylation of Indoles

Borylated indoles are versatile building blocks for functional molecules, such as pharmaceutical and natural products. However, the C-H borylation regioselectivity of unprotected indoles with seven distinct sites has been a problem for a long time. Among the various synthetic approaches to borylated indoles, transition-metal-catalyzed, electrophilic C-H borylation and chelation effect directed C-H borylation are attractive methods because of their powerful ability to rapidly construct various C-H borylation of indoles. In this review, we highlight the developments in the C-H borylation regioselectivity of indole using these methods of C-H borylation over the last 20 years. With a focus on the mechanism of the C-H borylation of indole, further studies and developments of this field would be inspired in the future.