The two alternative rate-determining steps in benzylic lithiation reactions of esters and Carbamates

Lithiation reactions of tertiary benzylic esters and carbamates have been studied. Kinetic methodology revealed that a two-step reaction pathway should be considered for these reactions, where either the lithium precomplexation and/or the proton transfer steps can be rate determining. Kinetic isotopic effects were evaluated by comparison of the lithiations of the corresponding protio/deutero substrates, and the results obtained support the notion that lithium precomplexation is taking place on the reaction pathway and that it is the rate-determining step in this transformation.This work was funded by the MINECO of Spain (CTQ2014-55208-P) and the Xunta de Galicia (GRC 2014/029)S