Synthesis of C1-Substituted 7-Oxanorbornadienes

Abstract

7-Oxanorbornadienes are valuable synthetic intermediates as they can serve as general templates to create highly substituted ring systems. However, to date, only very few C1-substituted 7-oxanorbornadienes have been synthesized and can be found in the literature. In this article, synthesis of some C1-substituted 7-oxanorbornadienes was achieved by the Diels–Alder reaction between 2-substituted furans and dimethylacetylene dicarboxylate. Moderate to good yields (13–85%) of the Diels–Alder reactions were observed. These C1-substituted 7-oxanorbornadienes will find applications as valuable synthetic intermediates and are useful in the studies of transition-metal-catalyzed reactions.

GRAPHICAL ABSTRACT

Keywords:

• Bicyclic alkenes
• Diels–Alder reaction
• dimethylacetylene dicarboxylate
• furan
• 7-oxanorbornadienes

ACKNOWLEDGMENTS

This work was supported by Merck Frosst Centre for Therapeutic Research, Natural Sciences and Engineering Research Council of Canada (NSERC), and Boehringer Ingelheim (Canada) Ltd.

Notes

^a Isolated yield after column chromatography.

^b Compound 11k was unstable and was aromatized to form compound 12 in 92% (see Scheme 3).