Iridium‐Catalyzed Direct Borylation of Five‐Membered Heteroarenes by Bis(pinacolato)diboron: Regioselective, Stoichiometric, and Room Temperature Reactions

An iridium(I) complex generated from 1/2[Ir(OMe)(COD)]2 and 4,4′‐di‐tert‐butyl‐2,2′‐bipyridine catalyzed the direct borylation of 2‐substituted thiophenes, furans and pyrroles in stoichiometric amounts relative to bis(pinacolato)diboron in hexane at room temperature. The heteroarylboronates from regioselective CH activation at the 5‐position were formed in high yields. Similar borylations of unsubstituted heteroarenes with an equimolar amount of the diboron regioselectively provided 2,5‐bis(boryl)heteroarenes.