Abstract
In the early 1950s Witkop described in a series of papers that oxidation of indoles with a variety of oxidation reagents leads to the formation of quinolones. The mechanism of this reaction involves the oxidative cleavage of the 2,3- double bond of the indole moiety (Witkop-oxidation) followed by a Camps-cyclization forming the quinolone ring. Winterfeldt identified conditions which allow a one pot Witkop-oxidation/Camps-cyclization sequence and applied this strategy for the synthesis of pyrrolo[2,3-c]quinolones starting from 1,2,3,4-tetrahydro-β-carbolines. This review gives a comprehensive description of all described examples of this reaction including a definition of scope and limitations and a discussion of the mechanism of this transformation.
Keywords: ozone, corynanthyrin, tetrahydroharman alkaloids, Peroxyacids, Autoxidation, singlett oxygen
Call for Papers in Thematic Issues
Catalytic C-H bond activation as a tool for functionalization of heterocycles
The major topic is the functionalization of heterocycles through catalyzed C-H bond activation. The strategies based on C-H activation not only provide straightforward formation of C-C or C-X bonds but, more importantly, allow for the avoidance of pre-functionalization of one or two of the cross-coupling partners. The beneficial impact of ...read more
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