The cation [RuCl(L)(eta(6)-mes)](+) [L = 4-isopropyl-2-(2-pyridyl)-1,3
-oxazoline] is synthesised diastereoselectively; treatment with AgSbF6
gives a dication which is an enantioselective catalyst for the asymme
tric Diels-Alder reaction between methacrolein and cyclopentadiene.