Transition Metal Diene Complexes in Organic Synthesis. Part-17 1. Studies directed towards the Iron-mediated Synthesis of 2-Oxygenated Carbazole Alkaloids

Institut fur Organische Chemie, Universitat Karlsruhe, Richard-Willstatter-Allee. 76131 Karlsruhe, Germany Manuscript received 6 October 1993 We describe some studies directed towards the synthesis of 2-oxygenated carbazole alkaloids by iron-mediated oxidative coupling of 1,3-cyclohexadiene and the corresponding 3-oxygenated aryiamine derivative. The process involves a consecutive formation of a carbon-carbon bond via electrophilic aromatic substitution with an iron-complexed cyclohexadienylium cation and subsequent carbon-nitrogen bond formation via oxidative cyclisation. Using this methodology a synthesis of the biogenetically important alkaloid 2-methoxy-3-methylcarbazole is described