Enantioselective Friedel-Crafts reaction of 4,7-dihydroindoles with beta-CF3-beta-disubstituted nitroalkenes

Using a Ni(ClO4)(2)-bisoxazoline complex as a catalyst, Friedel-Crafts alkylations of 4,7-dihydroindoles with beta-CF3-beta-disubstituted nitroalkenes were carried out with high enantioselectivities (up to 91%) to give alkylated dihydroindoles bearing trifluoromethylated all-carbon quaternary stereocenters in good yields. The corresponding chiral C2 alkylated indoles were obtained with complete preservation of enantiomeric purity by oxidation with 2,3-dichloro-5,6-dicyano-1,4-benzoquinone (DDQ).