Fused pyrimidines composed of alternating heteroatoms and a pyrimidine moiety were synthesized efficiently using readily available starting material 4-hydroxycoumarin, aromatic aldehydes, and urea/thiourea at room temperature.
Diversely functionalized chromeno-pyrimidine-2,5-dione/thione compounds were synthesized by cyclocondensation of 4-hydroxy coumarin, aldehydes and urea/thiourea using tannic acid as a green catalyst and 1:1 (EtOH:H2O) as a green solvent. Different acids were screened for their catalytic activity of chromeno-pyrimidine-2,5-dione/thione derivatives. Tannic acid (10 mol%) was used as a suitable catalyst with increased catalytic activity. By utilizing this protocol, chromeno-pyrimidine scaffolds were prepared in acceptable to excellent yield without the use of conventional volatile organic solvent and toxic metal catalyst. To our best of knowledge, this is the first report, in which tannic acid is utilized successfully as an eco-safe catalyst for synthesis of fused pyrimidines.
Novel heterocyclic dihydropyrimidine chromenopyrimidine-2,5-diones and thioxochromenopyrimidin-5-ones were synthesised by a three-component reaction between 4-hydroxycoumarin, urea or thiourea, and aromatic aldehydes in H2O under reflux in the presence of sodium dodecyl sulfate (20 mol%) and two drops of acetic acid. The products were obtained in good yields and their structures of all the synthesised compounds were established by spectroscopic methods..