6-Endo Heck Cyclization of 3-(2-Iodophenoxy)methylbenzofurans: A Useful Approach to Pterocarpenes

Abstract

Mitsunobu coupling of 3-hydroxymethylbenzofurans with o-iodophenols affords 3-(2-iodophenoxy)methylbenzofurans which under go a useful 6-endo Heck cyclization under Jeffery conditions to afford pterocarpene-type heterocycles. The unsubstituted parent pterocarpene thus prepared was readily converted to coumestan via subsequent PCC oxidation.

Supplemental materials are available for this article. Go to the publisher's online edition of Synthetic Communications® to view the free supplemental file.

GRAPHICAL ABSTRACT

Keywords:

• Coumestan
• 6-endo cyclization
• Heck reaction
• 3-hydroxymethylbenzofuran
• isoflavonoid
• Mitsunobu reaction
• o-iodophenol
• pterocarpene

ACKNOWLEDGMENTS

We gratefully acknowledge the donors to the Petroleum Research Fund, administered by the American Chemical Society, for partial support of the work. K. F. also thanks the Department of Chemistry for a summer research fellowship.