Thioethers from thioketones

Azine approach. Cyclization by oxidative formation of the S—N bond is frequently the final step in isothiazole syntheses. This approach can be used in the synthesis of the parent cation from the thioformyl precursor (129). 2-Substituted derivatives would require thioketone precursors and such compounds are more readily available as vinyl thioethers, e.g. (130). Bromine is used for the oxidative cyclization in this instance giving (13lj (73CC150). 

Some preliminary studies indicate that non-enolizable thioketones react with acid chlorides in the presence of Na2pe(CO)4 to give thioesters whereas enoliz-able thioketones lead to unsaturated thioesters i.e. 5-acyl enol thioethers). A new, readily-available reagent, 2-thiopyridyl chloroformate, has been found to be highly suited to the preparation of versatile 2-pyridinethioesters directly from carboxylic acids. ... 

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