Aggregative activation in heterocyclic chemistry. Part 4. Metallation of 2-methoxypyridine: unusual behaviour of the new unimetal superbase BuLi–Me2N(CH2)2OLi (BuLi–LiDMAE)

Abstract

A series of potential unimetal superbases BuLi–ROLi has been studied in order to increase the basicity/nucleophilicity ratio ([B/N]R) of BuLi. The best [B/N]R ratio is found with BuLi–LiDMAE. This complex base apparently metallates 2-methoxypyridine at the unexpected C-6 position. It is shown that no actual metallated species are formed in the reaction medium, the reaction occurring as the result of a common radical precursor stabilized by an aggregate cluster. Finally, as an application, C-6 substituted 2-methoxypyridines have been obtained in good to excellent yields.