2-Aminobiphenyl Palladacycles: The “Most Powerful” Precatalysts in C–C and C–Heteroatom Cross-Couplings

Abstract

New approaches to the Pd-catalysis employing palladacycle precatalysts have been recently developed. Breakthroughs in this area using 2-aminobiphenyl palladacycle precatalysts are highlighted. High reactivity and selectivity are achieved for the C–C and C–heteroatom bond formation under mild reaction conditions.

Controllable Activation of Pd‐G3 Palladacycle Precatalyst in the Presence of Thiosugars: Rapid Access to 1‐Aminobiphenyl Thioglycoside Atropoisomers at Room Temperature

“…Thus, reaction of 1 a with XantPhos Pd‐G3 in the presence of Et 3 N (1.2 equiv) in H 2 O:THF (8:2, v/v) for 2 h at room temperature led to complete conversion of the precatalyst into the carbazole 3 together with sugar disulfide 4 but the desired compound 2 a was not detected (Table , entry 1). This result is not surprising since the activation of the precatalyst in the presence of Et 3 N is well known . To overcome the formation of this undesired carbazole 3 , we conducted the model reaction in the presence of 0.5 equivalents of Et 3 N. Under these conditions compound 2 a was isolated in an acceptable 56 % yield together with the carbazole 3 and the disulfide 4 (entry 2).…”

Dialkylterphenyl Phosphine‐Based Palladium Precatalysts for Efficient Aryl Amination of N‐Nucleophiles

“…Precatalyst 2 b , with the weakly coordinating BAr F anion, was the less efficient. Probably, the large size of BAr F − brings it close enough to the Pd II cationic species to slow the intermolecular interaction with the base rendering the LPd 0 catalytic species . Overall, the best performances were obtained with palladacycles 4 d and 4 e bearing the bulkiest ligands L4 and L5 , respectively, which provided the highest yields of product at 0.5 mol % catalyst loading without using any excess phosphine ligand .…”

Efficient Buchwald–Hartwig–Migita Cross‐Coupling for DNA Thioglycoconjugation

“…In our efforts to functionalize sugars under transition‐metal catalysis, our group recently reported an efficient protocol for the palladium‐catalyzed coupling of aryl and alkenyl halides with various α‐ and β‐glycosyl thiols . The C−S bond‐forming reaction was rapidly achieved (5 min) at room temperature by using G 3 ‐XantPhos palladacycle pre‐catalyst (1 mol %), in the presence of Et 3 N (1.0 equiv) in THF. We envisioned in the present study whether 5‐iodo 2′‐deoxyuridine (5‐IdU) moiety could be utilized as building blocks for the synthesis of a range of thioglyco‐oligonucleotides (Scheme ).…”