NH4Cl催化微波照射合成3,4-二氢嘧啶-2-酮衍生物

经典的Biginelli反应用HCl作催化剂,通常产率较低(20%～50%).本文用NH4Cl作为催化剂,反应中用元水乙醇作溶剂,在微波辐射下反应.此改进方法具有催化剂廉价易得、反应时间短、收率高、操作简便等优点.本文所制得的9种3,4-二氢嘧啶-2-酮类化合物,收率较经典的Biginelli反应收率有较大的提高.该方法的使用为3,4-二氢嘧啶-2-酮衍生物的制备提供了一条方便、快捷、有效的合成方法.

Ammonium chloride-catalyzed one-pot synthesis of 3,4-dihydropyrimidin-2-(1 H)-ones by microwave irradiation

The classical synthesis of dihydropyrimidinones involves the one-pot condensation of ethyl acetoacetate, aromatic aldehyde and urea or thiourea under refluxing conditions. This method often provides the products in moderate yields, in particular when substituted aromatic aldehydes or thioureas are employed. An efficient synthesis of 3,4-dihydropyrimi dinones from the aldehyde, 1,3-dicarbonyl compounds and urea or thiourea in ethanol, using ammonium chloride as the catalyst under microwave irradiation, is described. Ammonium chloride is a very inexpensive and readily available reagent. Compared with the classical Biginelli reaction conditions, in which hydrochloric acid is used as the catalyst, this new method not only preserves the simplicity of Biginelli's one-pot reaction but also consistently produces 80-92% yields of the dihydropyrimidine-2-ones. In summary, it is an economically and environmentally friendly procedure for the synthesis of 3,4-dihydropyrimidin-2-(1H)-ones with short reaction times.