Elaboration of 1,8‐naphthyridine‐2,7‐dicarboxaldehyde into novel 2,7‐dimethylimine derivatives |
| |
Authors: | Choua Vu Deedee Walker Jason Wells Stephen Fox |
| |
Abstract: | The known 1,8‐naphthyridine‐2,7‐dicarboxaldehyde was prepared by SeO2 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‐naph‐thyridine‐2,7‐dicarboxaldehyde with various primary amines (R = ‐C6H11, ‐CH2C6H5, ‐C(CH3)3, ‐C10H15, and CH2CH2SCH2CH3) 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) 1H nmr shift and v(C=N) in the ir spectrum appear around 8.50 δ and 1640 cm?1, respectively, for the series 1(a‐e) . These novel naph‐thyridines typically display the signature 1H 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. |
| |
Keywords: | |
|
|