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.