Evidence for Bromine-Lithium Exchange in a Local High Concentration Gradient

Article abstract of DOI:10.1016/S0040-4020(01)90452-1

The product ratios for bromine-lithium exchange of 3,3'-dibromostilbene (6) with one equivalent of n-butyl lithium, s-butyl lithium or t-butyl lithium in THF and in Et2O to give after quenching with methanol 3-bromostilbene (7) and stilbene (8), have been investigated.In the reactive cases the ratio of 8:7 is significantly greater than expected for a statistical reaction.The apparently accelerated exchange of 7-Li relative to 6 is attributed to reaction in a high local concentration of the butyl lithium reagent.