Palladium-catalyzed ligand-free and aqueous Suzuki reaction for the construction of (hetero)aryl-substituted triphenylamine derivatives

Abstract

This paper reports an efficient synthesis of triphenylamine (TPA) derivatives via a palladium-catalyzed Suzuki reaction of (hetero)aryl halides with 4-(diphenylamino)phenylboronic acid (DPBA) in aqueous ethanol under aerobic and ligand-free conditions. Heteroaryl halides, namely pyridyl bromides, quinolyl bromides, pyrimidinyl bromides, 2-chloropyrazine and sulfur-containing heteroaryl bromides, could react smoothly with DPBA, affording good to excellent yields under mild conditions. In addition, aryl bromides were also successfully employed in the cross-couplings with DPBA and furnished the products in high yields at room temperature. The cross-coupling of 4-bromobenzonitrile with DPBA gave the desired product in a quantitative yield within 2 min, resulting in a TOF up to 5820 h 21 .

Alcoholic solvent‐assisted ligand‐free room temperature Suzuki–Miyauracross‐coupling reaction

“…in the early 1980s for Stille cross‐coupling reactions and later for Suzuki reactions in water and aqueous media . Consequently, various ligand‐free conditions have been applied in palladium‐catalysed Suzuki–Miyaura reactions which unlock new opportunities in catalysis for this vital reaction …”

Palladium-Catalyzed Ligand-Free Suzuki Reaction of Potassium Aryltrifluoroborates in Aqueous Ethanol

“…[26] : 1 H NMR (400 MHz, CDCl 3 ) δ: 9.15 (s, 1H), 8.92 (s,2H),7.44 (d,J＝8.8 Hz,2H),7.30 (t,J＝8.0 Hz,4H),7.16 (t,J＝8.8 Hz,6H),7.09 (t,J＝7.2 Hz,2H). [26] : 1 H NMR (400 MHz, CDCl 3 ) δ: 7.48～7.46 (m, 2H), 7.28～7.21 (m, 6H),…”

“…N,N-二苯基-4-(5-氟 2-吡啶基)苯胺 [26] : 1 H NMR (400 MHz, CDCl 3 ) δ: 8.50 (d,J＝2.8 Hz,1H),7.81 (d,J＝8.8 Hz,2H),7.67～7.64 (m,1H),7.46～7.41 (m,1H),7.28 (d,J＝8.3 Hz,4H),7.15～7.12 (m,6H),7.05 (t,J＝7.2 Hz,2H).…”

“…N,N-二 苯 基 -4-(5-甲 氧 基 -2-吡 啶 基 ) 苯 胺 [26] : 1 H NMR (400 MHz, CDCl 3 ) δ: 8.35 (d, J＝4.4 Hz, 1H), 7.81～7.79 (m, 2H), 7.60 (d,J＝8.0 Hz,1H),7.28～7.23 (m,5H),7.14～7.11 (m,6H),7.05～7.01 (m,2H),3.89 (s,3H). [26] : 1 H NMR (400 MHz, CDCl 3 ) δ: 9.15 (s, 1H), 8.92 (s,2H),7.44 (d,J＝8.8 Hz,2H),7.30 (t,J＝8.0 Hz,4H),7.16 (t,J＝8.8 Hz,6H),7.09 (t,J＝7.2 Hz,2H).…”

“…2-(2-噻吩基)吡嗪 [22] : [26] : 1 H NMR (400 MHz, CDCl 3 ) δ: 8.65 (d,J＝4.8 Hz,1H),7.87 (d,J＝8.8 Hz,2H),7.72～7.66 (m,2H),7.29～7.25 (m,4H),7.19～ 7.13 (m,7H),7.05 (t,J＝7.2 Hz,2H).…”