On the Cycloaddition Approach to Indolocarbazoles

Article abstract of DOI:10.1016/0040-4020(95)00735-Q

2,2'-Biindolyl 9 reacts with electron-deficient dienophiles at 100-110 deg C to give low to moderate yields of Michael addition and formal <4+2> cycloaddition products, with the former predominant; the products derived from 9 and 2-(phenylsulphinyl)maleimides 14 and 15 undergo in situ elimination of benzenesulphenic acid, leading to 2,2'-biindolyl-substituted maleimides which can be efficiently photocyclised into indolo<2,3-a>carbazoles.