Functionalization of the 3‐Position of Thiophene and Benzo[b]thiophene Moieties by Palladium‐Catalyzed CC Bond Forming Reactions using Diazonium Salts

Abstract

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.

Benign Arylations of Dimethyl Itaconate via Heck–Matsuda Reaction Utilizing in‐Situ Generated Palladium on Aluminum Oxide

“…The reason for this could be found in an intermolecular or intramolecular stabilization of the palladium after the oxidative addition or in a catalyst poisoning by the thiophene sulfur. Since in the literature the above mentioned diazonium salt was successfully converted by Raduán et al with ethyl acrylate and by Brunner et al with butanone in the Heck–Matsuda reaction, catalyst poisoning seems unlikely , …”

Styrylsulfonates and ‐Sulfonamides through Pd‐Catalysed Matsuda–Heck Reactions of Vinylsulfonic Acid Derivatives and Arenediazonium Salts

“…The reasons might be, as mentioned above, the comparatively high reaction temperatures and the occasionally reported high loadings of Pd precatalysts and expensive ligands. Based on our own and others' positive experiences with arene diazonium salts as electrophilic coupling partners in Pd‐catalysed coupling reactions, we investigated these reagents in the Heck reactions of vinylsulfonates and vinylsulfonamides. Heck reactions using arene diazonium salts were pioneered by Matsuda and coworkers in the late 1970's, and are therefore referred to as Matsuda–Heck reactions .…”

Dimethyl Sulfoxide-Accelerated Reductive Deamination of Aromatic Amines with T-BuONO in Tetrahydrofuran

“…We then examined the feasibility of this protocol for the deutero-deamination of aromatic amines 2a using d 8 -THF as solvent. According to 1 H NMR analysis, the deuterated 3a' and 3a were isolated in 93% yield with 93:7 D/H ratio. Finally, we performed the deamination of 2a in THF using 2,2,6,6-tetramethylpiperidinyl-1-oxy radical (TEMPO) as a radical trap (Scheme 2) and adduct 7 was isolated in 35% yield after purification.…”

“…GC analysis was determined by an Agilent Technologies 6890N Network GC System and Agilent Technologies 7683B Series Injector. 1 H NMR and 13 C NMR were recorded on a Varian Mercury Plus 400 instrument at 400 and 100 MHz, respectively, and TMS was used as internal standard. Mass spectra were measured with a Thermo Finnigan LCQ-Advantage instrument.…”