Metal-catalysed Grignard reaction with sulfides and dithioacetals

6 Metal-catalysed Grignard reaction with sulfides and dithioacetals 

The nickel-catalysed reaction of aryl, allyl or vinyl sulfides with Grignard reagents has been found to be an effective way for the conversion of carbon-sulfur bonds into carbon-carbon bonds [318]. However, simple aliphatic substrates are inert. 

Developments of such cross-coupling processes to dithioacetals were reported by Luh and reviewed [319], They led to a variety of applications for carbon-carbon single and double bond formation. The gem-dialkylation of allylic and benzylic dithioacetals is a good example of their interest. 

Another very important aspect of these transition metal-catalysed cross-coupling reactions stems from the high selectivity observed with stereo-defined vinyl sulfides. Applications to the stereoselective syntheses of pheromones were straightforward (see [321] and references therein), as shown in the two-step synthesis of muscalure from (Z)-l-bromo-2-phenylthioethylene [322] involving its sequential coupling through the bromo and phenylthio substituents with the appropriate derivatives. 

7 Reactions of n-halo sulfides with silyl enolates 

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