Oxidation of Tetrahydro-β-carbolines by Persulfate.

The development of persulfate-mediated oxidation of tetrahydro-β-carbolines is reported. This mild reaction facilitates the formation of a variety of 2-formyl N-substituted tryptamines and the related derivatives as key intermediates in moderate to excellent yields. The method is applicable to direct last-stage oxidation of two interesting pharmaceuticals, Cialis and evodiamine.