Abstract:The palladium-catalyzed Matsuda-Heck and Suzuki-Miyaura cross-couplings of 2-methoxycarbonylthiophene-3-diazonium tetrafluoroborate 1 were performed to synthesize a series of thiophene derivatives functionalized in the b-position. Good to excellent yields of the cross-coupling products were obtained using palladium acetate [PdA C H T U N G T R E N N U N G (OAc) 2 ], a ligandless palladium catalyst, without a base, at room temperature, under aerobic conditions and with short reaction times. A diazotization and cross-coupling sequence can also be performed in a one-pot process avoiding the isolation of the thiophenediazonium salt derivative. In addition, 2-methoxycarbonylbenzo[b]thiophene-3-diazonium tetrafluoroborate 8 was also efficiently arylated by applying the same Suzuki-Miyaura optimized reaction conditions.

Functionalization of the 3-Position of Thiophene and Benzo[b]thiophene Moieties by Palladium-Catalyzed C-C Bond Forming Reactions Using Diazonium Salts. -The Matsuda-Heck reactions and Suzuki-Miyaura cross-couplings are performed without ligand and base at room temperature, under aerobic conditions and in short reaction times. A diazotization and cross-coupling sequence can also be performed in a one-pot process avoiding the isolation of the thiophenediazonium salt derivative. -(RADUAN, M.; PADROSA, J.; PLA-QUINTANA, A.; PARELLA, T.; ROGLANS*, A.; Adv.