Highly enantioselective Friedel-Crafts reaction of 4,7-dihydroindoles with imines by chiral phosphoric acids: Facile access to 2-indolyl methanamine derivatives

A study was conducted to demonstrate the highly enantioselective Friedel-Crafts reaction of 4,7-dihydroindoles with imines and oxidation of the produces with by chiral phosphoric acids. The study examined the reaction between 4,7-dihydroindole and imine catalyzed by different chiral phosphoric acids. The study also found that lowering the temperature can decrease the reaction rate and increase the enantioselectivity. The study found that reaction with 1.1 equivalents of 4,7-dihydroindole gave 93% yield with 99% ee. The study developed a one-pot procedure with Friedel-Crafts reaction of 4,7-dihydroindoles for the synthesis of 2-indolyl methanamine derivatives. The study obtained 2-indolyl methanamine derivatives with fine enantioselectivities and provide a method to synthesize enantiopure 2-(4,7-dihydroindolyl) and 2-indolyl methanamine derivatives.