Zeolite-catalyzed ecofriendly synthesis of vibrindole A and bis(indolyl)methanes

Electrophilic substitution of indoles with carbonyl compounds was carried out over HY, Hβ and H-ZSM-5 zeolites as effective heterogeneous catalysts. These zeolites afford good to excellent yield of bis(indolyl)methanes at room temperature. Vibrindole A, a novel beneficial compound, has been successfully synthesised for the first time in the presence of zeolite in good yield. The yield of bis(indolyl)methanes increases in the order H-ZSM-5 < Hβ < HY, which is in accordance with the acid site density of the catalyst. The catalysts can be reused five times without any loss in catalytic activity.