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).