The chemistry of novel cyclic diesters : dialkoxy disulfide, thionosulfite and carbonate

• Main Author: Eghbali, Nicolas Dara.
• Format: Thesis
• Language: English
• Published: McGill University 2007
• Subjects: Sulfides; Carbonic acid
• Online Access: http://digitool.Library.McGill.CA:80/R/?func=dbin-jump-full&object_id=103380

The synthesis and chemistry of some new cyclic diesters were investigated. The first part of the thesis is concerned with the study of new cyclic diesters derived from thiosulfurous acid, namely cyclic dialkoxy disulfides and their structural thionosulfite isomers. The second part focuses on the development of a new methodology for the synthesis of cyclic carbonates (carbonic acid diesters). The synthesis of new cyclic dialkoxy-disulfides is described in Chapter 3. Five new molecules have been synthesized and fully characterized. An X-ray structure was obtained for the 2,3-furandimethylene dialkoxy disulfide. The substrates were prepared in an attempt to rationalize some of the existing limitations of the synthetic methodology. The relationship and possible interconversion between the newly prepared cyclic dialkoxy disulfides and their structural thionosulfite isomers were investigated. Benzene dimethanoate disulfide was successfully converted to its structural thionosulfite isomer under acidic conditions. Further investigations show the existence of a reversible sulfur extrusion process between thionosulfite and sulfoxylate. This sequential transformation brings the first chemical demonstration that branched bond sulfur can indeed be involved in sulfur extrusion as was first predicted by Foss in 1950. Finally, a highly efficient method to convert alkenes and CO2 into cyclic carbonates directly in water is presented in the second part of the thesis. Using N-bromosuccinimide (NBS) together with 1,8-diazabicyclo [5,4,0] undec-7-ene (DBU) in water, alkenes were converted into cyclic carbonates nearly quantitatively. Cyclic carbonates were also formed efficiently by using a catalytic amount of bromide ion together with aqueous hydrogen peroxide.