Cationic aqua complex derived from bidentate inda-box ligand and Cu(Cl
O4)(2). 6H(2)O is an excellent catalyst (5-10 mol%) for enantioselecti
ve (92-99% ee) Diels-Alder reactions of cyclopentadiene and various bi
dentate dienophiles. (C) 1998 Elsevier Science Ltd. All rights reserve
d.