Triflic acid controlled successive annelation of aromatic sulfonamides: An efficient one-pot synthesis of N-sulfonyl pyrroles, indoles and carbazoles

A novel one-pot synthesis of N-substituted heterocycles via successive cyclization/annelation starting from primary sulfonamides is described. This process leads directly to N-sulfonyl pyrroles, indoles and carbazoles. The selection of appropriate reactant/triflic acid ratio successfully controls the formation of the desired product.