Ortholithiation kinetic isotope effects

A further investigation of the ortholithiation of anisole has taken advantage of previous spectroscopic evidence of the exclusive formation of disolvated dimers of n-BuLi in TMEDA, combined with rate studies which demonstrate that this combination promotes ortholithiation via [(n-BuLi)2((TMEDA)2(anisole)] in pentane. The substantial kinetic isotope effect fcbs(H)/ obs(D) = 20 3] found on comparison of anisole with anisole- fg is indicative of rate-determining proton transfer but the unusually high value has not been explained satisfactorily. 

Attempts to use intermolecular and intramolecular kinetic isotope effects (KIE s) to identify a complexation step during ortholithiation have so far been inconclusive. Both intramolecular and intermolecular KIE s for the deprotonation of 2 and 3 by s-BuLi... 

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