Photochemical cycloaddition reagents for rigidly attaching the 1, 4-dimethoxynaphthalene chromophore to scaffold alkenes

The norbornanecyclobutene epoxides 1a−1c containing a fused 1,4-dimethoxynaphthalene chromophore have been reacted with cyclobutenes, cyclohexenes, norbornenes, 7-isopropylidenenorbornenes, 7-azanorbornenes, and other cyclic or electron-deficient alkenes at room temperature to form 1:1 adducts in stereoselective 1,3-dipolar cycloaddition reactions; alkynes can also participate in this reaction. The ability to form 2:1 adducts has also been demonstrated, thereby opening up opportunities for preparing functionalized products with large chromophore separations.