A highly efficient and aerobic protocol for the synthesis of N-heteroaryl substituted 9-arylcarbazolyl derivatives via a palladium-catalyzed ligand-free Suzuki reaction

Abstract

A palladium-catalyzed aerobic and ligand-free Suzuki reaction in aqueous ethanol has been developed for the synthesis of N-heteroaryl substituted 9-arylcarbazolyl derivatives. A number of N-heteroaryl halides, namely 2-halogenated pyridines, 2-bromoquinoline, 5-bromopyrimidine and 2-chloropyrazine, were coupled with 4-(9H-carbazol-9-yl)phenylboronic acid (CPBA) or 9-phenyl-9H-carbazol-3-ylboronic acid (PCBA) efficiently to afford good to excellent yields in a short reaction time. Moreover, the catalytic system of Pd(OAc)(2)-EtOH/H(2)O-K(2)CO(3) was successfully extended to the cross-couplings of N-heteroaryl halides with various arylboronic acids. The results demonstrated that the cross-coupling reaction in the present protocol was promoted by oxygen.

Trifluoromethyl-substituted cyclometalated iridiumIII emitters with high photostability for continuous oxygen sensing

“…53 The synthetic procedure for ligands L1-L4: a mixture of 2-pyridyl bromide, 1.5 equiv. 53 The synthetic procedure for ligands L1-L4: a mixture of 2-pyridyl bromide, 1.5 equiv.…”

2‐Phenylquinoline‐Based Cyclometalated Platinum(II) Complexes: Synthesis and Structure–Photoelectric Properties Relationship in Oxygen Sensing

“…Cyclometalating ligands with a quinoline moiety L1 – L9 were synthesized through an efficient ligand‐free Suzuki reaction,18 and were then used to synthesize new Pt II complexes in two distinctive steps, as reported previously (Scheme ) 19. The synthetic procedure for the cyclometalating ligands L1 – L9 is described in the following.…”

“…Ligands L1 – L9 :18 A mixture of 2‐bromoquinoline, arylboronic acid (1.5 equiv), K 2 CO 3 (2 equiv), Pd(OAc) 2 (1.5 mol %), and ethanol/distilled water (3:1 v/v) was stirred at 80 °C in air for an indicated time. The reaction mixture was added to brine (15 mL) and extracted four times with ethyl acetate (4×15 mL).…”

“…Driven by the ongoing exploration of new luminescent materials for oxygen sensing, inspired by these intriguing studies on 2‐phenylquinoline, and in continuation of our research on cyclometalated Pt II complexes, herein we report the synthesis and photoelectric performances of novel 2‐phenylquinoline‐based cyclometalated Pt II complexes (Scheme ). The 2‐phenylquinoline derivatives used in this study were prepared efficiently through a Pd‐catalyzed ligand‐free and aerobic Suzuki reaction in aqueous ethanol, as developed recently by our group;18 these compounds will be used to investigate the relationship between the structure and photoelectric properties of the novel Pt II complexes, and to evaluate their performances in oxygen sensing.…”

The Suzuki cross‐coupling reaction in pure water catalyzed by ligandless palladium using polyethylene glycol derivatives as surfactant

“…Thus industrial application of the Suzuki reaction – the standard methodology for the synthesis of biaryl units – remains challenging. One approach that circumvents the issue is the use of a ligandless palladium catalyst, for which a large number of strategies have been developed . More importantly, the ‘ligand‐free’ catalytic system makes it possible to carry out the Suzuki reaction under an aerobic atmosphere and/or in aqueous media.…”