**12. Benzo[4,5]thiazolopyrimido[5,4-d]pyrimidines**

Medhabati *et al*. [90] reported the synthesis of 2-thio-5-arylbenzo[4,5] thiazolopyrimido[5,4-d]pyrimidin-4-one derivatives under aqueous medium. Benzo[4,5]thiazolopyrimido[5,4-d]pyrimidines were synthesized by condensation

**Figure 14.** *Synthesis of 2-thio-5-arylbenzo[4,5]thiazolopyrimido[5,4-d]pyrimidin-4-ones.*

of thiobarbituric acids, 2-aminobenzothiazole and aldehydes using metal-proline as catalyst (**Figure 14**).
