The unprotected acid undergoes lithiation at the 2-position with 2.2 moles of s-BuLi in the presence of TMEDA; subsequent reaction with dibromotetrachloroethane provides access to 2-bromo-3-chlorobenzoic acid: Tetrahedron Lett., 36, 881 (1995); Bull. Soc. Chim. Fr., 133, 133 (1996).