Practical Palladium Catalysts for C-N and C-O Bond Formation

Highly Reactive, General and Long-Lived Catalysts for Palladium-Catalyzed Amination of Heteroaryl and Aryl Chlorides, Bromides, and Iodides: Scope and Structure–Activity Relationships

“…12 The steric hindrance of the catalyst did not prohibit reactions of more sterically hindered primary amines. tert-Butylamine reacted in good yield with 3-chloropyridine ( Enantiomerically enriched amines containing stereogenic centers α to the nitrogen have been shown to undergo racemerization in competition with cross-coupling when Pd(0) and monodendate ligands, such as P(o-tolyl) 3 or PPh 3 , were used as the catalyst. 57,58 This racemerization is proposed to result from reversible β-hydrogen elimination, which should occur more readily from complexes containing monophosphine ligands than from those containing bisphosphine ligands.…”

“…[46][47][48][49] Replacement of phosphine ligands in the catalyst by primary amine nucleophiles or by heteroaryl substrates through a basic heterocyclic nitrogen is one possible side reaction that limits the lifetime of the catalyst. Ammonia, 50 pyridine 50 and benzylamine 51 have been shown to displace the phosphine from the arylpalladium(II) halide complex {Pd[P(o-tolyl) 3 ](Ar) (Br)} 2 (Ar = p-tol, p-t BuC 6 H 4 ). 50 More recently, benzylamine and pyridine have been shown do displace the phosphine from Pd[P(t-Bu) 3 ](Ar)(Br) (Ar=o-tol, Ph) to form [Pd (pyridine) 2 (o-tol)Br] and [Pd(PhCH 2 NH 2 ) 2 (Ph)Br] and free ligand.…”

“…Ammonia, 50 pyridine 50 and benzylamine 51 have been shown to displace the phosphine from the arylpalladium(II) halide complex {Pd[P(o-tolyl) 3 ](Ar) (Br)} 2 (Ar = p-tol, p-t BuC 6 H 4 ). 50 More recently, benzylamine and pyridine have been shown do displace the phosphine from Pd[P(t-Bu) 3 ](Ar)(Br) (Ar=o-tol, Ph) to form [Pd (pyridine) 2 (o-tol)Br] and [Pd(PhCH 2 NH 2 ) 2 (Ph)Br] and free ligand. 52 Apparently the high basicity of the alkylphosphine does not sufficiently stabilize the Pd(II)-P bond toward the less hindered nitrogen donors.…”

Biaryl Phosphane Ligands in Palladium‐Catalyzed Amination

“…[53,54] Palladium-catalyzed amination has rapidly become an important tool in organic synthesis, pharmaceutical and materials science. [55][56][57][58][59][60][61][62][63][64][65][66][67][68][69] Progress in this reaction have been driven largely by the implementation of new classes of ligands. Initial studies made use of tri-otolylphosphine.…”

Palladium‐Mediated Fluorination of Arylboronic Acids

“…Our strategy is illustrated in equation 1, and consists of the synthesis of new aryl palladium complexes that react with the electrophilic fluorination reagent Selectfluor ™ [18] to afford fluoroarenes. Our initial investigations for the design of transition-metal complexes that afford efficient fluorination was guided by the observation that palladium has been successfully employed in several carbon-heteroatom bond formations, [19,20] including carbon-fluorine bonds for specific substrates. [14,21] Additionally, the development of our methodology was directed by the necessity to predict and control the exact location of fluorination and the need to introduce fluorine at any desired aromatic position.…”