Developing Bis(imino)acenaphthene-Supported N-Heterocyclic Carbene Palladium Precatalysts for Direct Arylation of Azoles

Abstract

On the basis of the strategy of developing highly efficient protocol for Pd-catalyzed cross-coupling reactions, a series of bulky bis­(imino)­acenaphthene (BIAN)-supported Pd-PEPPSI complexes were synthesized, characterized, and applied in direct arylation of azoles. The effect of backbone and N-moieties on NHCs was evaluated, and the reaction conditions were optimized. It was found that the bulky Pd-PEPPSI complexes could be successfully employed in cross-coupling of (hetero)­aryl bromides with azoles at a low palladium loading of 0.5–0.05 mol % under aerobic conditions, demonstrating the ease of manipulation without glovebox and handling of solvents.

Palladium‐Based Catalysts Supported by Unsymmetrical XYC–1 Type Pincer Ligands: C5 Arylation of Imidazoles and Synthesis of Octinoxate Utilizing the Mizoroki–Heck Reaction

“…A comparison of the catalytic properties of C1 – C4 reported in the recent past for direct arylation of aryl halide derivatives were investigated. Liu and co‐workers reported Pd(II) complexes derived from bis(imino)acenaphthene‐supported N‐heterocyclic carbene (loading 0.5 mol‐%), which less effective to C1 – C4 . Lee and co‐workers recently reported imidazopyridine‐based abnormal carbene ligands based palladium catalyst (catalyst loading 0.5 mol‐%), which has less effect.…”

“…5‐(3‐Methoxyphenyl)‐1,2‐dimethyl‐1H‐imidazole (4aj): Off‐white solid. Yield 153.7 mg, 76 % (Catalyst C1 ), 151.7 mg, 75 % (Catalyst C2 ) 161.8 mg, 80 % (Catalyst C3 ), 167.9 mg, 83 % (Catalyst C4 ); 1 H‐NMR (500 MHz, CDCl 3 ) δ = 7.33 (t, J = 7.8 Hz, 1H), 6.96–6.91 (m, 2H), 6.89 (d, J = 6.2 Hz, 2H), 3.82 (s, 3H), 3.52 (s, 3H), 2.43 (s, 3H).…”

“…3‐(1,2‐Dimethyl‐1H‐imidazol‐5‐yl)pyridine (3ak): Light yellow liquid. Yield 135.1 mg, 78 % (Catalyst C1 ), 140.3 mg, 81 % (Catalyst C2 ) 143.8 mg, 83 % (Catalyst C3 ), 148.9 mg, 86 % (Catalyst C4 ); 1 H‐NMR (400 MHz, CDCl 3 ) δ = 8.60 (d, J = 3.0 Hz, 1H), 8.55 (dd, J = 4.9, 1.7 Hz, 1H), 7.66–7.62 (m, 1H), 7.33 (dd, J = 7.5, 5.3 Hz, 1H), 6.98 (s, 1H), 3.51 (s, 3H), 2.43 (s, 3H).…”

Dimetallic Palladium‐NHC Complexes: Synthesis, Characterization, and Catalytic Application for Direct C−H Arylation Reaction of Heteroaromatics with Aryl Chlorides

“…The superior catalytic performance of 2 b was again demonstrated in our preparation of 5 i′ , 5 e′ , and 9 a , which were previously prepared exclusively from the corresponding aryl bromides, not chlorides. In a literature example, 2‐bromotoluene was used for the preparation of 5 i ′ in the presence of 2.5–5.0 mol% Pd loading and gave yields in the range of 35–68%, compared to a 71% yield for our reaction conditions (see entry 3) .…”

2‐Hydroxyethyl‐Substituted Pd‐PEPPSI Complexes: Synthesis, Characterization and the Catalytic Activity in the Suzuki‐Miyaura Reaction for Aryl Chlorides in Aqueous Media

“…They synthesized and characterized the organopalladium catalysts (PEPPSI complexes) and examined their catalytic activities in C–C and C‐heteroatom, bond formation. Also, new PEPPSI complexes have been synthesized and their catalytic activities in direct arylation and Suzuki‐Miyaura cross‐coupling reaction have been examined lately.…”