Iridium-catalyzed borylation of thiophenes: versatile, synthetic elaboration founded on selective C–H functionalization

Iridium-catalyzed borylation has been applied to various substituted thiophenes to synthesize poly-functionalized thiophenes in good to excellent yields. Apart from common functionalities compatible with iridium-catalyzed borylations, additional functional group tolerance to acyl (COMe) and trimethylsilyl (TMS) groups was also observed. High regioselectivities were observed in borylation of 3- and 2,5-di-substituted thiophenes. Electrophilic aromatic C–H/C–Si bromination on thiophene boronate esters is shown to take place without breaking the C–B bond, and one-pot C–H borylation/Suzuki–Miyaura cross-coupling has been accomplished on 2- and 3-borylated thiophenes.