A method of synthesizing o-bis(3-indolyl)arenes was developed by reacting indoles with 7oxabicyclo[2.2.1]hept-5-en-2-one and derivatives thereof having no aromatic ring. All 23 unknown o-bis(3indolyl)arenes could be obtained using this method. Palladium catalysis is useful for enlarging the πconjugated area of o-bis(3-indolyl)arenes, delivering aryl-, alkynyl-, and alkenyl-unit-installed o-bis(3indolyl)arenes, and benzo[c]indolo[2,3-a]carbazoles, the derivatization to which is effective for raising fluorescence quantum yield. A possible reaction mechanism is proposed based on several mechanistic studies.

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