Rhodium(II)-Catalyzed Site-Selective Intramolecular Insertion of Aryldiazoacetates into Unactivated Primary C−H Bond: A Direct Route to 2-Unsubstituted Indanes

Dirhodium(II)-catalyzed intramolecular insertion of aryldiazoacetates into an unactivated primary C−H bond was described in this study. The insertion reaction of aryldiazoacetates with ortho-isopropyl or ortho-ethyl groups in the presence of a catalytic amount of dirhodium(II) tetrakis(triphenylacetate), Rh₂(tpa)₄, at room temperature proceeded site-selectively to afford 2-unsubstituted indane-1-carboxylates in 75%–96% yields. In the case of o-isopropyl-substituted aryldiazoacetates, cis-isomers were obtained as major products. Furthermore, a chemoselective C−H insertion reaction of aryldiazoacetate bearing 1-oxyethyl-substituent at the ortho position was achieved by using a bulky and electron-deficient pivaloyl group as the protecting group of a highly active oxygen atom. The present reaction provided a direct route to 2-unsubstituted indanes. (Figure presented.).