The known 1,8-naphthyridine-2,7-dicarboxaldehyde was prepared by SeO 2 oxidation of 2,7-dimethyl-1,8-naphthyridine. The dimethylated naphthyridine molecule was assembled from an adaptation of the Skraup synthesis using 2-amino-6-methylpyridine and crotonaldehyde to afford a reproducible 37% yield, and constitute a significant advance over the literature of this reaction. The condensation of 1,8-naphthyridine-2,7-dicarboxaldehyde with various primary amines (R = -C 6 H 11 , -CH 2 C 6 H 5 , -C(CH 3 ) 3 , -C 10 H 15 , and CH 2 CH 2 SCH 2 CH 3 ) in alcohol affords diimines 1(a-e). The inherent crystallinity of 1(a-e) affords pure compounds in reasonable to excellent yields (ca. 70%) after evaporation of solvent and recrystallization. The anticipated spectroscopic features of (N=C-H) 1 H nmr shift and ν(C=N) in the ir spectrum appear around 8.50 δ and 1640 cm -1 , respectively, for the series 1(a-e). These novel naphthyridines typically display the signature 1 H nmr doublets at ca. 8.15-8.30 δ ascribed to the 3 and 4 naphthyridine protons, consistent with a mirror plane (through the quaternary carbons) perpendicular to the naphthyridine plane, and syn, syn relationships of the naphthyridine moiety with each imine nitrogen lone pair. Complexation studies of 1(a-e) with transition metals of biological relevance such as copper(I) and copper(II) will be reported elsewhere.

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