[reaction: see text] Exposing 2-fluorobenzoic acid (1a) to 2.2 equiv of LTMP at ca. -78 degrees C leads to deprotonation at the 3-position whereas 2-chloro/bromobenzoic acids (1b,c) are lithiated adjacent to the carboxylate. The resulting dianions 3Li-1a and 6Li-1b,c are trapped as such by chlorotrimethylsilane. In the absence of internal quench, 6Li-1b,c isomerize to the more stable 3Li-1b,c. The
2-Cbloro-6-substituted benzoic acids of the type 2a-h were prepared by the tandem metallation sequence from 2-chlorobenzoic acid 1 with the 1:1 complex sec-butyllithium/TMEDA in THF at -78 degrees C followed by quenching with electrophiles.