Cation electrophilic catalysis has been studied in nucleophilic substitution reactions of octyl methanesulfonate (1) promoted by complexes of macrocyclic polyethers 2–5 with alkali and alkaline-earth metal salts in chlorobenzene. The catalytic effect increases with increasing Lewis acid character of the cation, in the order Cs+∼ Rb+∼ K+ < Na+ < Li+ and Ba2+ < Sr2+ < Ca2+, and is mainly related to the