Lewis acid-catalysed ketene dithioacetal functionalization

8 Lewis acid-catalysed ketene dithioacetal functionalization 

A carbocation obtained from an a-unsaturated orthoester can be added to a ketene dithioacetal as shown [54], 

2 ThiophUic versus carbophilic addition of organometallics to a C=S bond. Carbanions through thiophilic addition 

Many examples of the nucleophilic attack of organometallic compounds at the sulfur atom of thiocarbonyl groups were reported in the 1970s by Beak, Vialle, Ohno, Schaumann and their co-workers [119,120, 327-329]. This thiophilic addition opens the way for a new method of preparation of carbanions a to sulfur. 

If the reaction is carried out on dithioesters. carbanions stabilized by two a-sulfur atoms are formed. Such carbanions are analogous to those obtained by deprotonation of dithioacetals, such as Corey-Seebach 

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