An Efficient and Economical Synthesis of 5,6-Diethyl-2,3-dihydro-1H-inden-2-amine Hydrochloride

An efficient and economical synthesis of 5,6-diethyl-2,3-dihydro-1H-inden-2-amine hydrochloride (1) utilizing 2-aminoindan as a cheap and commercially readily available starting material is described. The newly developed synthesis involves six-steps with 49% overall yield, and it introduces two ethyl groups at the 5- and 6-positions via sequential regioselective Friedel−Crafts acetylations and hydrogenations of N-protected-2-aminoindan. The Friedel−Crafts acetylations can be carried out neat with high regioselectivity using acetyl chloride as the reagent as well as the solvent, thus avoiding the use of halogenated solvents.