The Diels-Alder cycloaddition reactions between cyclopentadiene and methacrolein are effectively catalyzed with the aluminum-modified mesoporous silica MCM-41 having a variety of metal cations in the pore such as Zn-,Co-,Ni- and La-MCM-41.The β zeolite (H-β)having protons in the pore shows a dramatically high catalytic activity in the same reaction to give a quantitative yield of cycloadducts at 0℃ in less than l h, and the dealuminated β zeolite is also a highly reactive catalyst.The Diels-Alder reactions of cyclopentadiene with 3-buten-2-one and 2-ethylacrolein are also activated with the H-β and Ni-MCM-41
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