Solvent-free solid acid-catalyzed electrophilic annelations:: A new green approach for the synthesis of substituted five-membered N-heterocycles

An effective microwave-induced, solid acid-catalyzed, environmentally benign synthesis of substituted pyrroles, indoles and carbazoles under solvent-free conditions is described. The new synthetic methodology is based on the use of a considerably strong solid acid, K-10 montmorillonite. Both the cyclialkylation of amines and annelation of pyr-roles and indoles have been completed within minutes and provided excellent (75-98%) yields with practically 100% selectivity.