omega-Heteroatom effect on the nickel-catalyzed reactions of benzylic thioethers with Grignard reagents

A study of the nickel-catalyzed reactions of benzylic thioethers with Grignard reagents sheds light on the role of the omega-heteroatom and of other structures on the C-S bond's reactivity. Thioethers with beta-hydrogens form an intermediate that undergoes beta elimination to yield an olefin (styrene). For the C-S bond to be activated, the leaving group must be able to yield an anion that can coordinate to the nickel to form the intermediate. The length of the chain connecting the heteroatom to the sulfur atom and the size of the aryl group offer steric hindrance to formation of the complex. A related reaction is also discussed.