Co(III) catalysed asymmetric ring-opening of epichlorohydrin by salicylaldehyde derivatives: reversal of enantioselectivity and rate acceleration on addition of AlCl_3

Using asymmetric Coba lt(III) salen catalysts, the ring-opening of epichlorohydrin by 2,3- dihydroxybenzaldehyde and 2,4- dihydroxybenzaldehyde was found to occur at the phenolic groups most distant from the aldehydic group. Switching catalysts afforded a reversal in enantioselectivity. For 2,3- dihydroxybenzaldehyde and salicylaldehyde, addition of AlCl_3 to the reaction mixture led to an increase in reaction rate without any decrease in product enantiopurity.