Selenium Dioxide Oxidations in the Indole Area. Synthesis of β-Carboline Alkaloids

Article abstract of DOI:10.1021/ja00342a045

A number of different piperidoindole systems have been subjected to oxidation with selenium dioxide.The bonding between the indole and piperidine unit has been varied to provide different systems, the oxidation of which has led to formation of either 2-acyl- or 3-acylindoles or fully aromatic β-carbolines, depending on the substrate chosen.The pattern of reactivity observed was in complete agreement with the ene mechanism proposed for selenium dioxide oxidations, and this can be employed to predict the regiochemistry of the oxidation.Use of this technology has resulted in a two-step synthesis of the indole alkaloid canthin-6-one (30a).