**11. Pyrazolopyrano-pyrimidinones**

Tricyclic fused pyrazolopyranopyrimidines were synthesized by one-pot, fourcomponent reaction of ethyl acetoacetate, hydrazine hydrate, aromatic aldehydes and barbituric acid in good to excellent yields (88–95%) [85]. Another method for the synthesis of pyrazolopyranopyrimidines was employed using DABCO as catalyst in water [86].

A new series of triheterocyclic compounds containing pyrazole, pyran, and pyrimidinone rings was synthesized via a one-pot condensation of ethylacetoacetate, hydrazine hydrate, barbituric acid, and aromatic aldehydes in the presence of catalytic amounts of titanium dioxide nanowires [87]. Various functional groups were well tolerated under the optimized reaction conditions. A highly efficient, green protocol, one-pot four-component reaction involving thiobarbituric acid, hydrazine hydrate, ethyl acetoacetate and aromatic aldehydes for the synthesis of 7-thioxopyrazolopyrano-pyrimidinone derivatives has been accomplished using SDS (sodium dodecyl sulphate) as a catalyst (**Figure 13**) [88]. The procedure offers the advantages of green solvent, easy work-up avoiding the chromatographic separation and use of inexpensive, biodegradable, reusable catalyst. These novel 7-thioxo-pyrazolopyranopyrimidinone derivatives were screened for antimicrobial, and antioxidant activities. It was found that 3-methyl-4-(2,4-dichlorophenyl)-6,8-diethyl-7-thioxo4,6,7,8-tetrahydropyrazolo[4′,3′:5,6]pyrano-[2,3-d]pyrimidin-5(1H)-one has shown high antifungal and anti-bacterial activities against the tested fungi and bacteria, which may be due to the presence of chlorine atoms [88]. All the prepared pyrazolopyranopyrimidines were tested as anti-inflammatory agents and some of them revealed moderate to potent anti-inflammatory activity [89].

**Figure 13.** *Synthesis of 7-thioxo-pyrazolopyrano-pyrimidinone derivatives.*
