Palladium-Catalyzed Synthesis of Symmetrical Biaryls Under Microwave Irradiation and Conventional Heating

Abstract

The activity of the [Pd{C₆H₄(CH₂N(CH₂Ph)₂)}(µ-Br)]₂ complex was investigated in the synthesis of symmetrical biaryls under both conventional and microwave irradiation conditions, and their results were compared. This complex is efficient, stable, and not sensitive to air or moisture and is a catalyst for the homo-coupling reaction of aryl iodides, bromides, and even chlorides. The products were produced in excellent yields in short reaction times using a catalytic amount of [Pd{C₆H₄(CH₂N(CH₂Ph)₂)(µ-Br)]₂ complex in N-methylpyrolidine (NMP) at 130 °C. In comparison to conventional heating conditions, the reactions under microwave irradiation gave better yields in shorter reaction times.

GRAPHICAL ABSTRACT

Keywords:

• Biaryls
• cyclopalladated catalyst
• homo-coupling reaction
• tribenzylamine

ACKNOWLEDGMENTS

We gratefully acknowledge the funding support received for this project from the Isfahan University of Technology (IUT), IR Iran, and Isfahan Science and Technology Town (ISTT), Iran. Further financial support from the Center of Excellence in Sensor and Green Chemistry Research (IUT) is gratefully acknowledged.

Notes

^a Reaction conditions: 4-iodoanisole (1 mmol), base (1 mmol), solvent (2 ml), and palladacycle A (0.3 mmol%).

^a Reaction conditions: 4-iodoanisole (1 mmol), K₂CO₃ (1 mmol), NMP (2 ml), and palladacycle A, 130 °C.

^a Reaction condition: aryl halide (1 mmol), K₂CO₃ (1 mmol), palladacycle catalyst A (0.5 mmol%), NMP (2 ml), 130 °C.

^b Isolated yield.

^a Reaction condition: aryl halide (1 mmol), K₂CO₃ (1 mmol), palladacycle catalyst A (0.5mmol%), NMP (2 ml), 130 °C, 600 W.

^b Isolated yield.