M. Sainsbury
1975
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Abstract
Publisher Summary This chapter presents the preparation methods and properties of dioxanes, oxathianes, and dithianes. 1,2-dioxanes are formed by the photochemical addition of oxygen to alkenes with antimony chloride as a catalyst. The dioxins presented in the chapter are prepared by the reaction of potassium dioxide with dibromides. The spiro derivative is formed by heating the tetraol with formaldehyde at 145°C with sulfuric acid. Meldrum's acid can be alkylated reductively with aldehydes or ketones in the presence of borane or dimethylamine complex to form a benzyl derivative. Traditionally, 1,3-dioxanes are prepared by reacting 1,3-glycols with aldehydes or ketones or their acetals in the presence of acid catalysts or cation exchange resins. Aryl methyl ketones and araldehydes react together in the presence of trimethylsilyl polyphosphate to give meso-2,4,6-triaryl-5-acyl-1,3-dioxanes in good yields under very mild conditions. 2-Methoxy-1,4-dioxanes are synthesized by Kolbe type anodic ring expansion reactions of the acetals. Ring cleavage and ring contraction occur when 2-nitro dithiins are S-methylated and treated with triethylamine.