A study on the BF3 directed lithiation of 3-chloro- and 3-bromopyridine

The reactions of 3-chloro- or 3-bromopyridine-BF3 adduct with LDA (1.1 equiv) followed by quenching with benzaldehyde or iodine gave the C-2 substituted product. However, with 2.2 equiv of LDA and dimethyl disulfide, a C-6 substituted product was obtained.