Synthesis of thienodolin

We report a total synthesis of the alkaloid thienodolin (1a), as well as its 5-chloro isomer 1b and its unsubstituted analogue 1c, in three steps from the corresponding oxindoles Ba-c. The preparation was achieved through an initial Vilsmeier-Haack-Arnold reaction (chloro-formylation) followed by protection at the indole nitrogen, creation of the fused thiophene ring by nucleophilic substitution at the 2-position and an intramolecular cyclization using mercaptoacetamide. This gave 1a, 1b and 1c in total yields of 42%, 35% and 37%, respectively. ((C) Wiley-VCH Verlag GmbH & Co. KGaA, 69451 Weinheim, Germany, 2004).