Calix[8]arene Sulfonic Acid Catalyzed Three-Component Reaction for Convenient Synthesis of 3,4-Dihydropyrimidin-2(1<i>H</i>)-ones/thiones under Ultrasonic Irradiation
for the famous Biginelli reaction. Underultrasonicirradiation, calix[8]arene sulfonic acid could efficiently catalyzed the three-componentreaction of aldehydes with ethyl acetoacetate and urea or thiourea in ethanol to afford the corresponding 3,4-dihydropyrimidin-2(1H)-ones/thiones in 46-93%. The advantages of this method are the easy isolated procedure, short reaction time and low cost of the
TaBr5-catalyzed Biginelli reaction: one-pot synthesis of 3,4-dihydropyrimidin-2-(1H)-ones/thiones under solvent-free conditions
作者:Naseem Ahmed、Johan E. van Lier
DOI:10.1016/j.tetlet.2007.06.005
日期:2007.7
An efficient TaBr5 (5–10 mol %)-catalyzed Biginelli reaction under solvent-free conditions for one-pot syntheses of 3,4-dihydropyrimidin-2-(1H)-ones (DHPMs) and their thione analogs is reported. The catalyst is stable at room temperature and employed under mild and environmentally friendly conditions.
Stable titanocene dichloride (Cp2TiCl2) was activated by the N-donor ligand urea to form [(MeO)2Ti(NHCONH2)]+, which catalyzed the Biginelli reaction to produce 3,4-dihydropyrimidin-2-(1H)-ones.