Product inhibition in nucleophilic aromatic substitution through DPPPent-supported π-arene catalysis

Abstract

<p>Nucleophilic aromatic substitution (SNAr) of fluorobenzene by morpholine at a bis(diphenylphosphino)pentane-supported ruthenim complex is investigated as a model system for π-arene catalysis through the synthesis and full characterization of proposed...</p>

As Nice as π: Aromatic Reactions Activated by π‐Coordination to Transition Metals

“…Reaction conditions involved a Ru cyclooctadiene catalyst, phosphine DPPPent ligand and additives TfOH and Et 3 SiH. Recently, Mueller and Schley carried out a detailed mechanistic study on the reaction between fluorobenzene and morpholine, under these catalytic conditions [52] . Product inhibition was observed and quantified, as the N ‐phenylmorpholine reaction product binds much more strongly to Ru than fluorobenzene ( K eq =2×10 3 for the equilibrium between the fluoro, 49 a , and morpholino species, 49 c ), limiting the rate of arene exchange (Figure 7 C).…”

“…Recently,M ueller and Schley carried out ad etailed mechanistics tudy on the reaction between fluoro- benzene and morpholine, under these catalytic conditions. [52] Product inhibition was observeda nd quantified, as the N-phenylmorpholine reaction product binds much more strongly to Ru than fluorobenzene (K eq = 2 10 3 for the equilibrium between the fluoro, 49 a,a nd morpholino species, 49 c), limiting the rate of arene exchange (Figure 7C). Furthermore, the resting state of catalysis was found to be ap reviously unknown Ru-hydride species 50 b (Table 1, Entry 2.…”

Ruthenium/η5-Phenoxo-Catalyzed Amination of Phenols with Amines

“…In the 2010s, the catalytic potential of ruthenium­(II) species in nucleophilic aromatic substitution of aryl fluorides emerged (Scheme a). Shibata demonstrated the catalytic reactivity of a Ru­(II) species bearing a PCP ligand, a design previously pioneered by Hartwig in the hydroamination of styrenes, in the amination of nonelectron-deficient aryl fluorides . Moreover, a monodentate phosphine P­( p -FC 6 H 4 ) 3 was also shown to be efficient in the amination via a ruthenium η 6 -fluorobenzene complex bearing two phosphine ligands as the key intermediate .…”

Nucleophilic Aromatic Substitution of Halobenzenes and Phenols with Catalysis by Arenophilic π Acids

“…Work aimed at achieving S N Ar reactions of unactivated halobenzenes with a catalytic amount of a π-acidic transition metal has met with only limited success. − Among the rare examples are Ru-catalyzed substitution reactions of halobenzenes with external nucleophiles, but these reactions require a large excess of the halide to facilitate arene displacement. − For example, in 2010, Shibata and colleagues reported Ru(II)-catalyzed S N Ar amination reactions of nonelectron-deficient fluorobenzene derivatives with secondary amines. − These reactions proceed in the presence of either a monodentate phosphine ligand or the bisphosphine ligand 1,5-bis(diphenylphosphino)pentane and provide anilines in moderate to good yields when 5 equiv of the fluorobenzene is used.…”