Synthesis of Norbornanes via Photosensitized Strain-Release Cycloaddition of Housane.

Norbornanes are important scaffolds in organic chemistry that have been used as synthetic intermediates and as core scaffolds in drugs. These are commonly prepared by Diels-Alder cycloaddition of cyclopentadiene and an alkene. While useful, the synthesis of bridgehead substitutions can be challenging. In this work, a photochemical strain-release cycloaddition of a housane and alkenes is disclosed to prepare bridgehead-substituted norbornanes. The reaction proceeds through energy-transfer activation of naphthyl-substituted housane and enables direct access to substitution patterns that are difficult to obtain through conventional approaches. A broad range of alkenes and alkynes is tolerated under the mild reaction conditions, providing a modular entry into structurally diverse norbornanes.