Synthesis of benzofuranofuran derivatives: Model of natural products

Several benzofuranofuran derivatives were synthesized employing intramolecu lar cycloaddition reactions of ketenes with alkenes. (Alkenyloxy)ketenes, p repared from the tosylate by treatment with triethylamine, easily undergo i ntramolecular [2 + 2] cycloaddition to give tricyclic benzocyclobutafuranon es. Baeyer-Villiger oxidation of the cycloadducts gives benzofurano-furanon es, which are closely related to natural products with anticoagulant and an timalarial properties.