REGIOCHEMISTRY OF INTRAMOLECULAR PHOTOCYCLOADDITION OF 1,3-DIOXIN-4-ONES TETHERED THROUGH THE KETAL CARBON

1,3-Dioxin-4-one photosubstrates were prepared by condensation of alke nones with ketoesters or formyl Meldrum's Acid. The resulting dioxinon es contained enone and alkene chromophores, linked through the ketal c arbon of the dioxinone ring. The dioxinones were irradiated and the re giochemistry of the photoproducts was established. Substrates with a t wo carbon tether gave head to head products, while substrates with a t hree or four carbon tether gave predominantly head to tail products. ( C) 1997 Elsevier Science Ltd.