engleski

First application of Hexaaquaaluminium(III) tetrafluoroborate as a mild, recyclable, non- hygroscopic acid catalyst in organic synthesis: A simple and efficient protocol for the multigram scale synthesis of 3, 4-Dihydropyrimidinones by Biginelli reaction

For the first time hexaaquaaluminium(III) tetrafluoroborate has been used as a mild acid catalyst in organic synthesis. A simple method of its preparation based on the reaction of aluminium triisopropoxide and tetrafluoroboric acid in isopropanol afforded catalyst of high purity and activity. The three component Biginelli condensation of acetoacetate esters, urea and aldehydes catalyzed by 10 mol% of [Al(H2O)6](BF4)3 in refluxing acetonitrile afforded 3, 4- dihydropyrimidonones in good to high yields on multigram scales. The tolerance to acid sensitive reactants such as thienyl and furyl carbaldehydes, applicability to sterically hindered β-ketoesters and simple recyclability without losing catalytic activity make this catalyst as good replacement to literature methods. The mechanism of the reaction includes formation of the so called “ureido- crotonate” rather than corresponding acylimino intermediate as found with Brønsted type catalysts.

3; 4-dihydropyrimidinone; Biginelli reaction; heterocycles; condensation; hexaaquaaluminium(III) tetrafluoroborate

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