Oxidative transformations of 6-trifluoromethyl-2H-thiopyran as a route to fluoro-containing thiopyranosides

The synthesis of cis- and trans-6-(trifluoromethyl)-3,4-dihydro-2H-thiopyran-3,4-diols from 6-(trifluoromethyl)-2H-thiopyran via an OsO4-catalysed dihydroxylation and bromohydroxylation–alkaline hydrolysis sequence is described. Acetylation of the diols followed by S-oxidation affords the corresponding cis- and trans-3,4-diacetoxy-6-(trifluoromethyl)-3,4-dihydro-2H-thiopyran S-oxides which reacted with acetic anhydride and boron trifluoride diethyl ether complex by an additive Pummerer pathway giving tetraacetyl derivatives of trifluoromethyl-containing thiopyranoses.