Functionalization of Acetalic C(sp3)-H Bonds by Scandium(III) Triflate-Catalyzed Intramolecular Redox Reactions: Tandem 1,4-Hydride Transfer/1,5-Cyclization Processes Leading to Protected 1-Indanones

A new C-C bond forming reaction leading to adjacent quaternary carbons is reported. It is a one-pot hydride shift/cyclization process facilitated by the hydricity of the acetalic C H bonds, with benzylidenemalonate fragments as electrophilic hydride acceptors, and the catalysis of scandium(III) triflate. The reaction products are 1,2-dihydroindane derivatives. Alkoxy and alkanethiolate groups can be also intramolecularly transferred from the acetalic carbon to the electrophilic benzylidenemalonate C=C bond.