By treatment with s-BuLi, s-BuLi/TMEDA, or t-BuLi at~-78° C, 4-fluoro-and 4-chlorobenzoic acids (1a, b) are metalated preferentially in the position adjacent to the carboxylate. A complete reversal in regioselectivity is observed for 1a when treated with LTMP; a sequential process involving a rapid intraaggregate lithiation through a quasi dianion complex “QUADAC” is postulated to explain the unusual reactivity of Me2S2 and I2.