Variations in site of lithiation of N-[(2-(4-Methoxyphenyl)ethyl)]pivalamide; Use in ring substitution

Lithiation of N-[(2-(4-methoxyphenyl)ethyl)]pivalamide at -20 to 0 oC with three mole equivalents of n-BuLi in anhydrous THF, followed by reactions with various electrophiles, gives high yields of products involving ring substitution ortho- to the pivaloylaminoethyl group, which was unexpected in view of earlier results reported with t-BuLi