BiOClO4·xH2O and Bi(OTf)3 as Efficient and Environmentally Benign Catalysts for Synthesis of Bis(indolyl)methanes in Solution and Under Ultrasound Irradiation

Electrophilic substitution reactions of indoles with various aldehydes and ketones using catalytic amounts of BiOClO4•xH2O and Bi(OTf)3 in acetonitrile at room temperature and under ultrasound irradiation afforded the corresponding bis(indolyl)methanes in good to excellent yields. Selective condensation of indoles with aldehydes in the presence of ketones can be performed with these catalysts.