Sulphites and Related Compounds

Cyclic Sulphites and Related Compounds.—Crxiformational aspects of these ring systems have continued to hold the major attention in this area. 

Carbon-13 n.m.r. has been brought into play in order to help further elucidate the complex conformational behaviour of the six-membered-ring sulphites since chemical-shift differences are generally more sensitive to 

The conformational behaviour of ethylene sulphites has been investigated by n.m.r. and i.r. spectroscopy. Based on i.r. stretching frequencies of the S=0 bond in different solvents, similarities in the various coupling ccmstants observed for different sulphites, and benzene-induced solvent shifts, it appeared that all sulphites studied existed in basically the same conformation (180) in solution. 

Details of the photolytic decomposition of several arylpinacol sulphites have been published. Photolysis of either meso- or dl-hydrobenzoin sulphite (181) in methanol gave a mixture consisting of benzyl methyl ether, 

Thermolysis of the 2,3-dispirocyclopropyl sulphite (182) afforded, in e-sumably via dicyclopropylidene oxide, the cyclobutantme (183). Benz-pinacol sulphite gave tetraphenylethylene oxide in virtually quantitative 

Ethylene sulphites have been obtained in good yield, albeit in only about 5% conversion, by irradiation of pentenes in the presence of SO2 and O at —20 °C for 24 h. The proposed photochemical process involved the triplet state of SO2 and a charge-transfer complex between SO2 and the alkene. The electron-diffraction spectra of trans,trans- and rr j,cw -l,2-dimethylethylene sulphite have been obtained. The derived structures agree with those based on n.m.r. data. 

Maroni, L. Cazaux, G. Chassaing, I. Prejzner, and L. T. Tran, Bull. Soc. chim. France, 

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