Indium-Catalyzed Annulation of 2-Aryl- and 2-Heteroarylindoles with Propargyl Ethers: Concise Synthesis and Photophysical Properties of Diverse Aryl- and Heteroaryl-Annulated[<i>a</i>]carbazoles
is applicable also to symmetrical dimers such as bithiophene and bifuran derivatives. Mechanisticstudies suggest that the first step is addition reaction initiated by regioselective nucleophilic attack of the C3 of 2-aryl- and 2-heteroarylindoles to the internal carbon atom of the C[triple bond]C bond in propargyl ethers. The next stage is ring-closing S(N)2 process kicking out the alkoxy group and