Syntheses of Benzo[b]furan-6-carbonitrile and 6-Cyanobenzo[b]furan-2-boronic Acid Pinacol Ester

Abstract

6-Cyanobenzo[b]furan-2-boronic acid pinacol ester (10) is a potentially useful two-point scaffold for the construction of specific compounds or compound libraries with benzofuran cores. Using a per-iodination/de-iodination strategy coupled with Sonogashira alkynylation and Cu-catalyzed heteroannulation, we have developed a procedure that allows the preparation of benzo[b]furan-6-carbonitrile (9) and 6-cyanobenzo[b]furan-2-boronic acid pinacol ester (10) in gram quantities.

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GRAPHICAL ABSTRACT

Keywords:

• Benzo[b]furan
• heteroannulation
• heterocycle synthesis
• Sonogashira alkynylation

ACKNOWLEDGMENTS

We thank Peter Mueller of the MIT crystallography facility for expert analysis of x-ray crystal structure data.

This publication was made possible in part by Grants R43 AI082799 and U01 AI082052 from the National Institute of Allergy and Infectious Disease (NIAID) at the National Institutes of Health (NIH).

Notes

^a The yield was determined from the weight of the crude product mixture, which contained only products 3 and 4.

^b The ratio of 3 and 4 was calculated from the integrations of the 3- and 3′-protons of the crude NMR.