A facile and efficient protocol has been developed for mild construction of fused pyrimidines via l -proline-catalyzed reaction of 4-hydroxy coumarins, aldehydes, and 2-aminobenzothiazoles/urea. The reaction has been carried out rapidly and efficiently in water under mild and metal-free conditions. Current etiquette has efficiently synthesized the heterocycles and avoids the use of hazardous solvents over conventional organic solvents. A plausible reaction mechanism has been established in this study. This study represents the first case in which l -proline as a homogeneous catalyst has been explored in the synthesis of fused pyrimidines in water in view of simple procedure and acceptable efficiency. This method gives the target product in excellent yield with ease of workup.

A conceptually new intramolecular Pauson-Khand reaction (IPKR) based general strategy has been demonstrated for the formal syntheses of isoboonein, iridomyrmecin and isoiridomyr-mecin from very cheap, commercially available starting material.

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.

One-pot condensation of 4-hydroxy coumarins, aldehydes and urea/thiourea to build C–C and C–N bonds is described.

An elegant Diels–Alder based approach has been demonstrated for the first racemic total synthesis of gramineusquinone B, iso-merrilliaquinone, iso-magnoshinin and 2-epi-3,4-dihydro magnoshinin.