The present work represents a continuation of the investigation of the chemistry of nitropyridine derivatives, based on the methodology for nitration of pyridines developed by Professor Jan M. Bakke and co-workers at NTNU. Nitropyridines have been utilized as substrates for the formation of novel bis- and tris-heterocyclic compounds, and new synthetic routes to fused heterocycles have been developed.
Several new β-carboline analogues and fused azacinnolines have been prepared based on a Suzuki coupling and subsequent cyclization approuch. The formation of 4-isocyanobut-2-enenitrile and 3-cyanopyrrole products by ring opening and ring contraction of 3-pyridyl nitrenes, respectively, is reported. 7-Azacinnolin-4(1H)-one has been prepared and tautomery investigated by NMR. The general ability of appropriate pyridyl compunds to undergo Friedländer condensation to give different 1,7-naphthyridines has been demonstrated. Bis-heterocyclic products have been prepared from methyl/allylpyridylketones fromed by Weinreb tranformations, and a method has been developed to allow for the preperation of reactive pure pyridylvinylketones to be used in further reactions, such as Diels-Alder cycloaddition reactions.