Exo-Selective Intramolecular C–H Alkylation with 1,1-Disubstituted Alkenes by Rare-Earth Catalysts: Construction of Indanes and Tetralins with an All-Carbon Quaternary Center

We report herein the exo-selective, regiospecific annulation of a wide range of functionalized aromatic substrates with 1,1-disubstituted alkenes through C­(sp2)–H and benzylic C­(sp3)–H activation by half-sandwich rare-earth catalysts. This protocol offers a straightforward and atom-efficient route for the synthesis of a family of indane and tetralin derivatives bearing an all-carbon quaternary stereocenter that were difficult to access previously by other catalysts. The reaction mechanism has been elucidated by deuterium-labeling experiments and DFT calculations.