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.