In general, heterocyclic compounds have evoked interest and concern because of their fundamental role in biological profiles and biological actions in nature. Now, most of the lead molecules in medicinal chemistry are based on hetero-atoms. In medicinal chemistry- to bring two hetero-atoms to the drug molecule, isoxazoles are interesting functional groups. Isoxazole as a key building block has been widely used and is an important heterocyclic unit.

Indeed, MCR technology is widely acknowledged now for its impact on drug discovery projects and is strongly supported by industry as well as academia. Uracil is an important one of the five nucleobases and significantly important because of their biological properties; of which 6-amino uracil is most important and can act as nucleophile and electrophile. 6-Aminouracils being rich are used as starting materials for the synthesis of heterocyclic compounds of biological significance such as pyrido-, pyrazolo, pyrimido and pyrimidines derivatives. 5,6,7,8-tetrahydropyrimido[4,5-d]pyrimidine-2,4(1H,3H)-dione have been synthesized by various conventional methods. However, these methods have drawbacks such as unsatisfactory yields and tedious work-up etc.  In the present work, we would like to report a new route for the synthesis of 5,6,7,8-tetrahydropyrimido[4,5-d]pyrimidine-2,4 (1H,3H)-dione in MCRs.