Controlling the regioselectivity of the ring opening of spiro-epoxyoxindoles for efficient synthesis of C(3)–N(1′)-bisindoles and C(3)–N(1′)-diindolylmethane

A strategy for the construction of both C(3)–N(1′) bisindoles and C(3)–N(1′) diindolylmethane has been explored via tuning of the nucleophilicity of indoline/indole to spiro-epoxyoxindole.