Acetals dithio-, acylation

Acylation66 of D-fructose leads67 to substantial yields of a completely esterified, acyclic derivative (6) in which the ketonic center exists as a free carbonyl group, and provides an indirect route for the synthesis of ketose dialkyl dithioacetals, as 6 reacts with two equivalents of thiol under acid catalysis to produce68 the acylated dithio-acetal 7, which can subsequently be saponified to yield the free... 

N-Acyl-B-enaminoketones (328), readily prepared from the potassium enolates of methyl ketones and diethyl N-(acyl)dithio-carbonimidates (327), are converted into 1,3-oxazinium salts (329) on treatment with 70% perchloric acid in acetic anhydride. The conversion of the 1,3-oxazinium salts to the corresponding... 

Trifluoroacetic anhydride added to a stirred mixture of the startg. ketene dithio-acetal and a little pyridine in chloroform, and allowed to stand 14 hrs. at room temp. -> product. Y 93%. F. e., also C-acylation of thioenolethers, s. Hojo, R. Masuda, and Y. Kamitori, Tetrah. Let. 1976, 1009. 

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