The deactivating effect of a meta‐methoxy group in the methoxydechlorination of pyridine and pyrimidine derivatives

Reactivity data and the activation parameters for the methoxydechlorination of some 2‐chloro‐4‐R‐pyridines and 4‐chloro‐6‐R‐pyrimidines have been determined. A methoxy group meta with respect to the reaction site is found to be deactivating as already observed in the quinoline series. This gives further support to the hypothesis that in N‐heteroaromatic systems a conjugative interaction of an electron‐releasing substituent with the aza group (s) is a factor in modifying the nucleophilic reactivity as predicted by Hammett's σm values.