Iridium-catalyzed C-H coupling reaction of heteroaromatic compounds with bis(pinacolato)diboron: regioselective synthesis of heteroarylboronates

The C-H coupling of aromatic heterocycles with bis(pinacolato)diboron was carried out in octane at 80 100degreesC in the presence of a 1/2-[IrCl(COD)](2)-(4,4'-di-tert-butyl-2,2'-bipyridine)catalyst (3 mol%). The reactions of five-membered substrates such as thiophene, furan, pyrrole, and their benzo-fused derivatives exclusively produced 2-borylated products, whereas those of six-membered heterocycles including pyridine and quinoline selectively occurred at the 3-position. Regioselective synthesis of bis(boryl)heteroaromaties was also achieved by using an almost equimolar amount of substrates and the diboron. (C) 2002 Elsevier Science Ltd. All rights reserved.