Synthesis of substituted 5,6,7,8-tetrafluoro-1H-benzo[f]indol-4,9-diones based on the reaction of hexafluoro-1,4-napthoquinone with methyl 3-aminocrotonates

For the first time, the possibility of using hexafluoro-1,4-naphthoquinone for the construction of condensed heterocyclic system was demonstrated. As a result, two-step synthesis of previously unknown 5,6,7,8-tetrafluoro-1H-benzo[f]indol-4,9-dione derivatives was elaborated. The suggested method includes initial interaction of hexafluoro-1,4-naphthoquinone with various methyl 3-aminocrotonates and subsequent intramolecular cyclization into the target fluorinated benzo[f]indole-4,9-diones. The distinctive feature of considered protocol is regiospecific reaction of fluorine atoms in quinone fragment. Advantages of the presented approach are simple synthetic procedure avoiding chromatographic purification, atom economy and readily available starting materials. The structure of one of the synthesized compounds was established by x-ray analysis.