Grovenstein-Zimmerman

In order to study this unusual dimerization in detail 49 [40] was synthesized and subjected to the same reaction conditions. The cumyl group inhibits the Grovenstein-Zimmerman rearrangement as in this case the formation of an anion at a tertiary center would be encountered, so only cleavage to the vinyllithium compound 18 is possible. Indeed, after reacting 49 with lithium metal for 4 h at room temperature and subsequent work-up with dimethyl sulfate the dimer 51 is isolated in 82 % yield, with t-butylbenzene (53) as the other product in 84 % yield (Scheme 11). 

---