Asymmetric friedel-crafts alkylations of indoles with ethyl glyoxylate catalyzed by (S)-BINOL-titanium(IV) complex: Direct access to enantiomerically enriched 3-indolyl(hydroxy) acetates

Enantioselective Friedel-Crafts alkylation reactions of a variety of indoles with ethyl glyoxylate, catalyzed by a chiral (S)-BINOL-Ti(IV) complex (10 mol%), are reported. The corresponding ethyl 3-indolyl(hydroxy)acetates were formed in good yields and with high enantiomeric excess (up to 96%). When methyl pyruvate or p-chlorophenylglyoxal was used, the bisindole compound was obtained in excellent yield. A possible mechanism is proposed.