Efficient Catalytic Kinetic Resolution of Spiro-epoxyoxindoles with Concomitant Asymmetric Friedel-Crafts Alkylation of Indoles

Abstract

An efficient process involving the catalytic kinetic resolution of racemic spiro-epoxyoxindoles with the simultaneous enantioselective Friedel-Crafts alkylation of indoles has been realized using a chiral phosphoric acid catalyst. The reaction provides two useful intermediates in high yields and excellent enantioselectivities. Performing the catalysis on a gram scale led to (R)-3-(3-indolyl)-oxindole-3-methanol, which was used in the asymmetric formal total synthesis of (+)-gliocladin C. Notably, the enantiomers (S)-3-(3-indolyl)-oxindole-3-methanol can be obtained easily by the reaction of the resolved spiro-epoxyoxindole with indole.

Keywords: alkylation; asymmetric catalysis; kinetic resolution; organocatalysis; spiro-compounds.