Gold(I)-Catalyzed Intramolecular Enantioselective Hydroarylation of Allenes with Indoles

Abstract
Treatment of 2-allenyl indole 4 with a catalytic 1:2 mixture of [(S)-2]Au2Cl2 [(S)-2 = (S)-3,5-tBu-4-MeO-MeOBIPHEP] and AgBF4 in toluene at −10 °C for 17 h led to isolation of tetrahydrocarbazole 5 in 88% yield with 92% ee. The protocol was effective for the cyclization of terminally disubstituted allenes and for the formation of seven-membered rings.