A typical π-acid tetracyanoethylene and capto-dative olefin dicyanoketene acetals were found to catalyze stereospecific alcoholysis of epoxides at the ambient temperature to 50° C in good yields. Mildness and significant chemoselectivity of the catalysts were demonstrated by intactness of tetrahydropyranyl ether and ethylene acetal groups. A novel regioselectivity associated with anchimeric assistance of the ethereal group on the side chain was ...