Enaminones in Heterocyclic Synthesis: A Novel Route to Tetrahydropyrimidines Dihydropyridines Triacylbenzenes and Naphthofurans under Microwave Irradiation

摘要

Condensation of phthalimidoacetone (>1) with DMFDMA (N,N-Dimethylformamide dimethyl acetal) has afforded enaminone >2. Refluxing >2 with equimolecular amounts of benzaldehyde and urea in acetic acid afforded a mixture of tetrahydropyrimidine >5 and the dihydropyridine >6. Compound >2 undergoes self-condensation on heating in acetic acid or under microwave irradiation in presence of acidic zeolite to give 1,3,5-triacylbenzene >9. Reacting enaminone >11a with naphthoquinone >15 afforded the naphthofuran >18. The possible formation of the aldehyde >19 was excluded based on an HMQC experiment, which revealed that the carbonyl carbon is not linked to any hydrogen.