Chapter 5.6 Five-membered ring systems: With O & S (Se, Te) atoms

Abstract

The conversion of carbonyl compounds into 1,3-dioxolanes by reaction with ethanediol over zeolite HSZ-360 is described in the chapter. The treatment of styrene oxide with ruthenium trichloride in acetone gives dioxolane. New methods for the synthesis of protected 3,4-dihydroxybutyrates and 1,3-dioxolane-4-methanols are described in the chapter. The reaction of acetylenic alcohols, HC≡C–C(OH)R 1 R 2 , with CO 2 and a quaternary ammonium or phosphonium salt and a silver salt gives the methylenedioxolanones. Treatment of the azetidine–dioxolane with diethylaluminium chloride results in isomerization of the pyrrolidine-dioxane. The formation of 1,3-dithiolanes from carbonyl compounds and ethane-1,2-dithiol can be achieved by microwave irradiation in the presence of a K-10 clay or by catalysis with WCl 6 . The latter method is also applicable to transdithioketalisation of 1,3-dioxolanes and these substrates as well as enamines, tosylhydrazones, and oximes may be converted into 1,3-dithiolanes using a natural kaolinitic clay. Treatment of adamantane-2-thione or fluorene-9-thione with ethyl diazoacetate gives the 1,3-dithiolanes with none of the alternative products expected from 1,5-electrocyclisation of the intermediate thiocarbonylides.