Nuclear magnetic resonance data of pyrido[2,3‐ B ] pyrazines and their σ‐adducts with amide ion and water

13 C nmr spectral data of the parent substance pyrido[2,3‐ b ]pyrazine and several of its derivatives (containing one or more chloro, amino, oxo, bromo, fluoro, phenyl, methyl, hydrazino or t ‐butyl substituents) are reported. The 13 C nmr spectrum of the parent substance has been assigned conclusively by 13 C ‐labelling. Additionally we proved, the existence of anionic 1:1 σ‐adducls i.e., 3‐amino‐3,4‐dihydropyrido[2,3‐ b ]pyrazine, the formation of 3‐amino‐2‐ t ‐butyl‐6‐chloro‐3,4‐dihydropyrido[2,3‐ b ]pyrazinide ion and by 1 H nmr spectroscopy 2‐amino‐1,2‐dihydro‐3‐phenylpyrido[2,3‐ b ]pyrazinide ion. The 13 C nmr data of the cation of the dihydrale 2,3‐dihydroxy‐1,2,3,4‐tetrahydropyrido[2,3‐ b ]pyrazine, present in a solution of the parent compound in N hydrochloric acid, are given.