It was found that these complexes can accelerate the rate of the D-A reactions, but almost had no effect on the ratio of endo to exo of the products by introduction of various substituents in comparison with the reaction in the absence of the catalyst.

• 实验结果表明：与没有催化剂的反应体系相比，这些稀土配合物能明显加快反应速度，但未能明显提高产物的内外型比例。