Biginelli reactions were well catalyzed on mesoporous silica MCM-41 (M41) whose activity was much greater than that of amorphous silica. Octane was the most suitable among 6 kinds of solvents examined. The addition of metal ions on M41 enhanced the catalytic activity in the order Al > Ti > Fe = In. Al-planted M41s with Si/Al ratios of 45–35 showed the highest catalytic activity and could be used repeatedly though a small loss of the activity was observed. The catalysis could widely be applied to obtain various substituted dihydropyrimidinones (DHPMs) with high yields, some of which were very difficult to prepare until now. In addition, Biginelli reactions were combined with formyl C–H insertion reactions of diazoester on mesoporous silica; that is, a tandem one-pot four-component DHPM synthesis was attempted. Acetaldehyde, ethyl diazoacetate, p-tolualdehyde, and urea could be condensed and the corresponding DHPM derivative was obtained with 50% yield on Al-planted M41.
介孔
二氧化硅 MC
M-41 (
M41) 能很好地催化 Biginelli 反应,其活性远远高于无定形
二氧化硅。在所考察的 6 种溶剂中,
辛烷是最合适的溶剂。在
M41 上添加
金属离子可提高催化活性,其顺序为 Al > Ti > Fe = In。
硅/铝比为 45-35 的铝植入
M41 显示出最高的催化活性,虽然活性略有下降,但仍可重复使用。该催化反应可广泛应用于高产率获得各种取代的二氢
嘧啶酮(
DHPM),其中一些到目前为止还很难制备。此外,还在介孔
二氧化硅上将 Biginelli 反应与重氮酯的甲酰基 C-H 插入反应相结合,即尝试了串联式一锅四组份
DHPM 合成。
乙醛、
重氮乙酸乙酯、对甲
苯酚和
尿素可以缩合,并在 Al-planted
M41 上得到相应的
DHPM 衍
生物,收率为 50%。