Regiochemistry of intramolecular photocycloaddition of 1,3-dioxin-4-ones tethered through the ketal carbon
摘要:
1,3-Dioxin-4-one photosubstrates were prepared by condensation of alkenones with ketoesters or formyl Meldrum's Acid. The resulting dioxinones contained enone and alkene chromophores, linked through the ketal carbon of the dioxinone ring. The dioxinones were irradiated and the regiochemistry of the photoproducts was established. Substrates with a two carbon tether gave head to head products, while substrates with a three or four carbon tether gave predominantly head to tail products. (C) 1997 Elsevier Science Ltd.