Gold-Catalyzed Synthesis of 2-Substituted, 2,3-Disubstituted and 1,2,3-Trisubstituted Indoles in [bmim]BF4

Cyclization of 2-alkynylanilines in the presence of NaAuCl(4)center dot H(2)O using [bmim]BF(4) as the reaction medium afforded 2substituted indoles in high yields. The catalyst system was best recycled using n-Bu(4)NAuCl4. 2,3-Disubstituted indoles could be prepared from 2-alkynylanilines and 3-buten-2-one through a one-flask annulation-alkylation sequence and 1,2,3 -trisubstituted indoles were obtained from the same starting materials via an aza-Michael addition-annulation-alkylation process.