Direct alkylation of pyrrole with vinyl substituted aromatics: versatile precursors for the synthesis of porphyrinoid macrocycles

5-Substituted dipyrromethane analogues (8), (23) and (25) were synthesized by the reaction of 2-vinyl-pyrroles, 2-vinylthiophene or 2-vinylbenzenes with excess pyrrole in the presence of Lewis acids. Accordingly, tripyrromethane analogues could be obtained by starting with 2,5-divinyl thiophene or 2,6-divinylbenzenes. The reaction usually gave moderate yields and catalyst-dependent was seen in some cases. The reaction is compatible with other reported dipyrromethane syntheses and could be applied for the construction of unusual porphyrins. (C) 2008 Elsevier Ltd. All rights reserved.