Simple, Convenient, and Efficient Synthesis of 2-Aryl-substituted Benzo[b]furans

Abstract

A simple, convenient, and efficient one-pot method for the preparation of benzofuran is reported. Sonogashira coupling reaction of aryl iodides with 2-methyl-3-butyn-2-ol was used as an acetylene source in the presence of Pd(PPh₃)₂Cl₂ and CuI. Deprotection of the acetylene moiety in the same pot using a strong base and the second Sonogashira coupling/cyclization of and substituted o-iodophenols led to the formation of the appropriate benzo[b]furans. These protocols also can be used in the synthesis of natural products and indoles.

Keywords:

• Aryl iodide
• benzo[b]furan
• 2-methyl-3-butyn-2-ol
• o-iodophenol
• Sonogashira reaction

ACKNOWLEDGMENT

The authors thank the State Key Laboratory of Applied Organic Chemistry for financial support.

Notes

^a Reacted in a 110 °C oil bath or at the boiling point of the solvent under an argon atmosphere for 24 h.

^b No benzofuran product was detected by TLC.

^a o-Iodophenols were prepared according to the literature procedure Ref.^{[ 13 ]}.

^a 0.02 mmol of Pd(OAc)₂ and 0.04 mmol of PPh₃ were used instead of Pd(PPh₃)₂Cl₂ and reacted at 50 °C in the first step.