Abstract
The multicomponent reaction of 5-aminopyrazole derivatives with cyclic 1,3-dicarbonyl compounds and dimethylformamide dimethylacetal (DMFDMA) in DMF at 150 °C under controlled microwave heating afforded regioselectively 8,9-dihydropyrazolo[1,5-a]quinazolin-6(7H)-ones 6 rather than the corresponding dihydropyrazolo[5,1-b]quinazolin-8(5H)-ones 4.
Highlights
Several naturally occurring and synthetic compounds containing quinazoline derivatives are of considerable interest in fields related to the organic and medicinal chemistry of natural products [1,2]
In continuation of our studies in which we performed multicomponent reactions using controlled microwave heating [22,23,24], we report the results of our investigation concerning the regioselectivity in multicomponent reactions of 5-aminopyrazoles, cyclic 1,3-diketones and dimethylformamide dimethylacetal (DMFDMA) under controlled microwave heating
The pyrazolo[1,5-a]-quinazolin-8(5H)-one 6a was established as the reaction product, and 13C NMR was in agreement with the proposed structure, rather than with isomeric 4a, which was prepared by first reacting 1a with dimedone (2a) in DMF under microwave heating at 150 °C for 10 min to afford 5
Summary
Several naturally occurring and synthetic compounds containing quinazoline derivatives are of considerable interest in fields related to the organic and medicinal chemistry of natural products [1,2]. The pyrazolo[1,5-a]-quinazolin-8(5H)-one 6a was established as the reaction product, and 13C NMR was in agreement with the proposed structure, rather than with isomeric 4a, which was prepared by first reacting 1a with dimedone (2a) in DMF under microwave heating at 150 °C for 10 min to afford 5.
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