One-Pot Reaction Sequence: N-Acylation/Pictet-Spengler Reaction/Intramolecular [4+2] Cycloaddition/Aromatization in the Synthesis of -Carboline Alkaloid Analogues

One-pot synthesis of tetrahydro-beta-carbolines, fused with an isoindole core, was proposed starting from maleic anhydride and azomethines easily available from tryptamines and 3-(hetaryl)-acroleins. This sequence includes four key steps: an acylation of the aldimine with maleic anhydride, a Pictet-Spengler cyclization, an intramolecular Diels-Alder reaction, and a concluding [1,3]-H shift. As a result, six- or seven-nuclear alkaloid-like heterocyclic systems, containing a benzo-[1,2]-indolizino-[8,7-b]-indole fragment annulated with furan, thiophene, or pyrrole, are formed in a diastereoselective manner.