Pyridopyridazines. II. Some reactions of Pyrido[2,3-d]- and Pyrido[3,4-d]-pyridazine

Pyridopyridazines have been oxidized under acid and alkaline conditions and the sites of oxidation have been rationalized on the basis of charge densities. Pyrido-[2,3-d]pyridazine has been brominated, aminated, and made to react with hypo-chlorous acid and with peracids. The positions of substitution and addition are discussed in relation to calculated π-electron densities and bond lengths. Attention is drawn to some unusual features of the N.M.R. spectra of 1,2-diazine N-oxides.