Tetrahydro-beta-carbolines 2 and 3 possessing a proton on nitrogen N-2 react with one molecule of activated alkyne to give, depending on the solvent, either enamines or heterocyclic derivatives of indolizino[8,7-b]indole skeleton. The enamines obtained can be quantitatively transformed into the same skeleton. The application of acidic or basic catalysis determines the position of the double bond in the pyrrole ring as well as the nature of the substituents in positions 1,2,3 and 11b. (C) 1999 Elsevier Science Ltd. All rights reserved.