Efficient synthesis of pentacyclic benzosultam-annulated thiopyranoindoles via domino Knoevenagel / intramolecular hetero-Diels-Alder reactions in water

A convenient catalyst-free synthesis of hitherto unknown pentacyclic benzosultam-annulated thiopyranoindole derivatives is reported which proceeds via domino Knoevenagel / intramolecular hetero-Diels-Alder reactions of (E)-N-alkyl-2-aryl-N-(2-formylphenyl)ethene-1-sulfonamides with indoline-2-thiones in water. The products were obtained regioselectively in high yields.