Efficient synthesis of bis(indolyl)methanes catalyzed by Lewis acids in ionic liquids

Efficient electrophilic substitution reactions of indoles with various aldehydes proceed smoothly in ionic liquids using Lewis acids, In(OTf) 3 , YbCl 3 , InCl 3 , BiCl 3 , and ZnCl 2 , to afford the corresponding bis(indolyl)methanes in high yields.