Microwave-Assisted Facile and Rapid Friedel–Crafts Benzoylation of Arenes Catalyzed by Bismuth Trifluoromethanesulfonate

Abstract

The catalytic activity of metal triflates was investigated in Friedel–Crafts benzoylation under microwave irradiation. Friedel–Crafts benzoylation with benzoyl chloride of a variety of arenes containing electron-rich and electron-poor rings using bismuth triflate under microwave irradiation is described. This method allows the preparation of aryl ketones under solventless conditions in good to excellent yields and short reaction time. Bismuth triflate was easily recovered and reused five times without significant loss of the catalytic activity.

GRAPHICAL ABSTRACT

Keywords:

• Aryl ketone
• bismuth triflate
• Friedel–Crafts benzoylation
• microwave irradiation

Notes

^a The mixture of anisole (1 mmol) and benzoyl chloride (1 mmol) with bismuth triflate was activated under monomode CEM microwave oven.

^b Conversion based on anisole was determined by GC-FID using naphthalene as internal standard.

^a Reaction conditions: anisole (1 mmol), benzoyl chloride (1 mmol), and metal triflate (0.1 mmol).

^b Conversion based on anisole was determined by GC using naphthalene as internal standard.

^c Yield in parentheses is isolated yield.

^a Reaction conditions: arene (1 mmol), benzoyl chloride (1 mmol), and bismuth triflate (0.1 mmol).

^b Low boiling substrates such as benzene, toluene, and fluorobenzene were used under high pressure (100 psi) and substrates with electron-withdrawing substituents such as acetophenone and nitrobenzene were not suitable for this method.

^c Isolated yield.

^d Isomer ratio was determined by GC-FID.

^a After the reaction, bismuth triflate was recovered from aqueous layer by removal of water under vacuum.

^b Isolated yield.

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