Trimethylene dithiotosylate, reactions with

Although it has been long known that trimethylene dithiotosylate can be prepared by the reaction of thiotosylate ion with trimethylene dibromide,3 5 various difficulties are associated with the preparation. These problems are to a considerable extent related to the mode of preparation and the resultant purity of potassium thiotosylate. The thiotosylate salt must be free of tosylate and p-toluenesulfiriate impurities, otherwise side products such as tosylates or sulfones will form. One such by-product, tosyltrimethylene thiotosylate,... 

Hydrogen sulfide is undesirable because its presence can lead to the formation of potassium p-toluenesulfinate. The latter can be formed by the desulfurization of thiotosylate by hydrogen sulfide generated in the reaction of potassium hydrosulfide with tosyl chloride. Attention should be directed toward control of the reaction temperature so that hydrogen sulfide is rapidly removed, thereby ensuing survival of the S—S bond of the thiotosylate. p-Toluenesulfinate ion can displace bromide to form stable sulfones which are less soluble in common solvents, such as benzene, than trimethylene dithiotosylate. Therefore, purification of the dithiotosylate contaminated with the sulfones is difficult to achieve by means of fractional recrystallization. 

Trimethylene dithiotosylate can react with activated methylene groups, enamines, or hydroxyethylene derivatives of carbonyl compounds to form dithiane derivatives. Ethylene dithiotosylate undergoes similar reactions to form dithiolanes.3 6... 

The preparation of dithianes from enamines by reaction with trimethylene dithiotosylate (propane-1,3-dithiol di-p-toluenesulfonate) has been applied with enamines derived from oholostan 3 one, aceto-acetic ester, and phenylacetone.6 7 Reactions of trimethylene dithiotosylate with hydroxymethylene derivatives of ketones also give rise to dithianes thus the hydroxymethylene derivative of cholest-4-en-3-one can be converted to 2,2-(trimethylenedithio)cholest-4-en-3-one. 1,3-Dithiolanes are obtained in a similar manner by reaction of ethylene dithiotosylate1 with the appropriately activated substrate.5,7... 

Geminal alkylation (4,212-213). The definitive paper on geminal alkylation of ketones via cyclobutanones has been published. The original method involves dibromination of the cyclobutanone and consequently is not suitable for substrates containing isolated double bonds. In this case an alternative approach is available via a-trimethylenedithiocyclobutanones. Direct condensation of trimethylene dithiotosylate (4, 539-540 5, 71) with the cyclobutanone enolate fails, but can be accomplished indirectly by conversion of the cyclobutanone into an enamide by reaction with i-butoxybis(dimethylamino)-methane. The desired dithiane is then obtained by reaction of the enamide and trimethylenedithiotosylate in ethanol buffered with potassium acetate. The sequence is illustrated for 1-tetralone (1). The product (4) obtained in this way... 

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