4-Chloropyridine was deprotonated on treatment with 1/3equiv of the highly coordinated magnesate Bu 3 (TMP)MgLi 2 in THF at −10°C, as evidenced by trapping with I 2 . The use of Bu(TMP) 2 MgLi in Et 2 O allowed the reaction of 2-chloropyridine, giving the 3-functionalized derivative as the main product. Mixtures of 3- and 4-functionalized derivatives were obtained when 2,6-dichloropyridine was involved in the reaction. Performing the reaction on 3-chloropyridine with lithium magnesates in THF, either the 4,4′-dimer or the 4-iodo derivative was formed after quenching by I 2 , the former using 1/3equiv of Bu 2 (TMP)MgLi and the latter using 1equiv of (TMP) 3 MgLi. Similar results were observed with 3,5-dichloropyridine, 2,5-dichloropyridine and 3-chloro-2-fluoropyridine. 1,2-Migration of the lithium arylmagnesate formed by deprotonation was proposed to justify the dimers formation.