Synthesis of 2-cyclopropyl-3-(5-aryl-1H-pyrazol-3-yl)-1,8-naphthyridine.

Background: 1,8-Naphthyridine derivatives have attracted considerable attention because the 1,8-naphthyridine skeleton is present in many compounds that have been isolated from natural substances, with various biological activities.

Findings: N,N-dimethoxy-N-methyl-1,8-naphthyridine-3-carboxamide (1) on reaction with Grignard reagent forms 2-methoxy-1,8-naphthyridine-3-carbaldehyde (2). Compound 2 on reaction with different aromatic aldehydes provided 1-(2-cyclopropyl-1,8-naphthyridin-3-yl)-3-arylprop-2-en-1-ones (3a-e) and these compounds on cyclisation with hydrazine hydrate 99% yielded 2-cyclopropyl-3-(5-aryl-1H-pyrazol-3-yl)-1,8-naphthyridines (4-a-e). Synthesis of the target compounds involved the formation of 4a-e. It was accomplished using Grignard reaction, condensation reaction, and cyclisation reactions. All the synthesized compounds were readily soluble in DMSO. Spectral data of the synthesized compounds were in full agreement with the proposed structures.

Conclusions: In conclusion, we have developed a simple and an efficient Synthesis of 2-cyclopropyl-3-(5-aryl-1H-pyrazol-3-yl)-1,8-naphthyridine.