Three methods for the conjugate addition of indoles to 2, 5-dichlorobenzoquinone have been developed. A wide variety of indoles substituted with halogen, alkyl, alkoxy, and aryl groups participate in anaerobic condensation reactions promoted by HCl, H2SO4, or CH3CO2H. The hydroquinone product is partially oxidized by excess dichlorobenzoquinone and fully converted to the 2, 5-dichloro-3-(indol-3-yl) benzoquinone targets by DDQ or ...
