in Wiley Online Library (wileyonlinelibrary.com).Novel simple, efficient, and eco-friendly synthetic procedure for preparation of pyrazolo [3,4-b]quinolin-5-ones based on three-component microwaves-assisted heterocyclization reaction of 5-aminopyrazoles, aromatic aldehydes, and dimedone in hot-water medium was developed. The new method allows obtaining target heterocycles in good and excellent yields and with high degree of purity.
Three-component reaction of 2-amino-4-arylimidazoles, aldehydes and dimedone or barbituric acid proceeds in an unusual direction and instead of imidazo[1,2-a]pyrimidine derivatives gives Knoevenagel-Michael adducts having abnormally low reactivity in heterocyclizations.
Green and Efficient Synthesis of Pyrazolo[3,4-b]quinolin-5-ones Derivatives by Microwave-Assisted Multicomponent Reaction in Hot WaterMedium. -The presence of 1.2 equivalents triethylamine and a reaction temperature of about 170 °C are crucial for the conversion. Application of other basic or acidic catalysts results in lower yields and no products are obtained without catalyst. -(ANDRIUSHCHENKO, A. Y.; DESENKO, S. M.; CHERNENKO, V. N.; CHEBANOV*, V. A.; J. Heterocycl. Chem. 48 (2011) 2, 365-367, http://dx.
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