Trichloroisocyanuric acid is found to be an efficient catalyst for the electrophilic substitution reaction of indole with aldehydes/ketones to afford the corresponding bis-indolyl, tris-indolyl, di(bis-indolyl), tri(bis-indolyl), and tetra(bis-indolyl)methanes under solid-state conditions by pulverization-activation method at room temperature with excellent yields. The remarkable features of this new procedure are high conversions, shorter reaction times, cleaner reaction profiles, and simple experimental and work-up procedures
