The effect of an alkoxy group on the kinetic and thermodynamic acidity of benzene and toluene

2-, 3- And 4-Methoxytoluene can be selectively metalated at an O-adjacent ortho position when butylithium or tert-butyllithium in the presence of sodium (potassium) tert-butoxide or N,N,N',N",N"-pentamethyldiethylenetriamine are employed as reagents. In contrast, lithium diisopropylamide or lithium 2,2,6,6-tetramethylpiperidide deprotonate the benzylic a-position of 2- and 3-methoxytoluene exclusively and of 4-methoxytoluene preferentially. These relative reactivities can be rationalized by an interplay of transition state stabilizing and destabilizing forces (dipole matching and metal coordination vs. lone pair repulsion). [on SciFinder (R)]