Reaction of 2-pyridyllithium with azine N-oxides. Simple and convenient method for the synthesis of 2,2′-bipyridine 1-oxide and 2,2′:6′,2″:6″2′″-tetrapyridine 1′-oxide
In the reaction of 2-pyridyllithium with quinoline 1-oxide and isoquinoline 2-oxide a nucleophilic substitution of hydrogen occurs to form the corresponding pyridin-2-ylquinolines. A dimerization of the substrate occurs with pyridine 1-oxide, 2,2′-bipyridine 1-oxide or quinoxaline N-oxide. A similar dimerization in good yield occurs when treating azine N-oxides with tert-butyllithium and this serves as a simple and convenient method for preparing bi- and tetrapyridines.