Synthesis of substituted tetrahydrofuranones and tetrahydropyranones: Photocycloaddition/fragmentation reactions of dioxinones

The combination of dioxinone aldol addition methodology and [2+2]-photocycloaddition/fragmentation reactions can provide access to substituted tetrahydrofuran-3-ones and tetrahydropyran-4-ones, subunits abundantly found in biologically active natural products. Intramolecular photocyclization of vinyl and allyl ethers with dioxinones, followed by fragmentation in alkaline MeOH (K2CO3) leads to tetrahydrofuran-3-ones and tetrahydropyran-4-ones, providing a practical route to versatile building blocks for complex molecule synthesis. (C) 1997 Elsevier Science Ltd.