The Hemetsberger reaction: A new approach to the synthesis of novel dihydroindoloindole systems

The Hemetsberger indole synthesis provides an alternative method for the preparation of dihydroindoloindole systems. Two novel examples, dimethyl 3,8-dihydroindolo[7,6-g]indole-2,7-dicarboxylate and dimethyl 1,6dihydroindolo[5,4-e]indole- 2,7-dicarboxylate, were succesfully prepared by the Hemetsberger indole sythesis. The ester functionality on the C-2 position was used for the further elaboration of these tetracyclic systems.