ChemInform Abstract: Claisen-Schmidt Condensation in the Solid State.

Abstract

An effici ent and co nv enient pro cedure for the prep arati on of 3cinnamoyl-2-methyl-I,8-naphthyridin es 2 has been ac hi eved by the Claisen-Schmidt condensa ti on of 3-acetyl-2-meth yl-I ,8 naphth yridin e 1 with aromatic ald ehydes in the pre se nce of KOH in the so lid sta te . Th e reacti on pro ceeds efficientl y at room temperature in good yields and in a state of high purity. Development of organic solid state reactions has emerged as a frontier area of research in synthetic organic chemistr/ · 6 . A convenient method for the synthesis of a, ~-unsaturated carbonyl compounds is highly desirable, because they are potenti a l precursors for the preparation of a vari ety of biodynamic heterocyclic compounds 7 - 9 . Claisen­ Schmidt condensation reacti on is one of th e most efficient methods for effecting carbon-carbon bond formation and has wide synthetic applications 10. In view of thi s, we present herein for th e first time the Claisen-Schmidt conde nsation in th e so lid state at room temperature. The starting compound, 3-acetyl-2-methyl- 1,8 naphthyridine 1 was obtained by the condensation of 2-aminonicotinaldehyde with acetylacetone ll . Claisen-Schmidt conde nsation of 1 with aromatic aldehydes in the presence of KOH in th e solid state at room temperature furnished th e corresponding 3cinnamoyl-2-methyl- I ,8-naphthyridines 2 in excell~nt yields. The reaction is fairly general, fac il e and efficient and is devoid of any side products. In a typical case, when an equimolar mi xture of 3acetyl-2-methyl- I ,8-naphthyridine 1, 3, 4-methylene­ dioxybenzalde hyde and KOH was ground by pestil e and mortar at roo m temperature for 10 min, th e mixture turned to a pale-yellow solid. The so lid was combined with ice-cold wate r and filt ered off. After usua l work-up 3-(3,4-meth ylenedioxyc innamoyl)-2meth yl-I, 8-naphthyridine 2c was obtained in 94% yield. It s structure was estab l ished by spectral data. AI