Nitroketene dithioacetals(2) were prepared in moderate to high yields by nitrodeacetylation reaction from α-acetyl ketenedithioacetals(1) when treated with mixed acid in dichloromethane at room temperature. This reaction involves an electrophilic addition-deacetylation mechanism and shows the nucleophilicity of the α-carbon atom in α-oxo ketenedithioacetals.
Bromo ketene dithioacetals (5) were prepared in high yields by reaction of α,α-diacetyl ketene dithioacetals (4) with bromine catalyzed by FeBr 3 at room temperature. This new reaction is proposed involving an ipso electrophilic addition-deacetylation mechanism.
As a kind of versatile synthons, α-oxoketene dithioacetals have found their wide utilizations in organic synthesis. Owing to the interaction between two electron donating groups(RS) and an electron withdrawing group in the α position, the α-carbon atom of α-EWG ketene S,S-acetals shows a high nucleophilicity. In this paper, the reactions of α-acetyl cyclic ketendithioacetals with a series of acyl chlorides were performed and a new route to the C～C bond formation reaction at the α-carbon atom of α-oxoketene dithioacetals was described. By the above reactions, α-acetyl-α-acyl ketendithioacetals were prepared with good to high yields(55%～82%) via the acylation of α-acetyl cyclic ketendithioacetals at the α-carbon atom of α-acetyl ketendithioacetals mediated by titanium tetrachloride in dry dichloromethane at reflux temperature. The mechanism of the acylation between compound 1 and acyl chloride was proposed, which belongs to nucleophilic addition-elimination reaction.
