An efficient synthesis of dihydropyrimidin-2(1H)-ones using samarium(III) nitrate hexahydrate as a catalyst from an aldehyde, 1,3-dicarbonyl compounds and urea under solventless conditions is described. Compared with the classical Biginelli reaction, the yields of this protocol increased from 20–50% to 78–98% while the reaction time was significantly shortened from 18 h to 15–30 min.
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3.
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