Hydroxy-Directed Enantioselective Hydroxyalkylation in the Carbocyclic Ring of Indoles.

A Cinchona-derived squaramide catalyzes the reaction between hydroxyindoles and isatins leading to enantioenriched indoles substituted in the carbocyclic ring. The reaction proceeds efficiently with differently substituted isatins, yielding the desired products with excellent regioselectivity, good yields, and high enantiocontrol. Moreover, every position of the carbocyclic ring of the indole can be functionalized by using the appropriate starting hydroxyindole. The OH group was removed smoothly upon hydrogenolysis of the corresponding triflate.