The Sc (OTf) 3-catalyzed Friedel-Crafts alkylation reaction with an alcohol, an arenecarbaldehyde or an arenecarbaldehyde acetal as the alkylating agent affords a diarylmethane or an allylbenzene derivative highly selectively. The salient feature of this reaction is that only a catalytic amount of Sc (OTf) 3 can effect the reaction. Furthermore, Sc (OTf) 3 is recoverable and reusable after the synthetic reaction. The Sc (OTf) 3-catalyzed ...