(±)-CSA catalyzed Friedel–Crafts alkylation of indoles with 3-ethoxycarbonyl-3-hydoxyisoindolin-1-one: an easy access of 3-ethoxycarbonyl-3-indolylisoindolin-1-ones bearing a quaternary α-amino acid moiety

For the first time, a very simple, efficient, mild, catalytic, and one-step procedure for the synthesis of a series of new 3-ethoxycarbonyl-3-indolylsubstituted-isoindol-1-one derivatives has been achieved via a Friedel–Crafts alkylation of indoles with 3-hydroxy-3-ethoxycarbonylisoindolin-1-one at room temperature using easily available inexpensive camphor-10-sulfonic acid as an organocatalyst. The current protocol provides good to excellent yields of the title compounds with high substrate scope. In addition, the desired product possesses a chiral quaternary carbon center at the 3-position on isoindolin-1-one ring which is flanked by indole moiety, amino and ester groups for further elaborations.