Copper-Catalyzed Synthesis of 5-Arylindolo[1,2-c]quinazolin-6(5H)-ones from 2-(2-Bromoaryl)indoles and Aryl Isocyanates under Microwave Irradiation

2-(2-Bromoaryl)indoles react with aryl isocyanates by microwave irradiation in the presence of catalytic CuI along with a base to afford 5-arylindolo[1,2-c]quinazolin-6(5H)-ones. The reaction is compatible with 2-(2-bromoaryl)indoles bearing straight and branched alkyl chains at position 3 of indole moiety. Both electron-donating and -withdrawing substituents on bromophenyl and indole moieties are well tolerated. The reaction proceeds through an initial nucleophilic addition of 2-(2-bromoaryl)indoles to aryl isocyanates. This is followed by an intramolecular C−N bond formation by an addition-elimination nucleophilic aromatic substitution via Meisenheimer complexes and a copper-catalyzed Ullmann-type coupling.