C–H-Activated Direct Arylation of Strong Benzothiadiazole and Quinoxaline-Based Electron Acceptors

Electron acceptors are important components of π-conjugated materials, but the strong electron-withdrawing properties of the required synthetic intermediates often make them poor substrates in synthetic schemes designed around conventional organometallic cross-coupling. Here, strong benzodiimine-based acceptors, including 5,6-difluoro­[2,1,3]­benzothiadiazole, 5,6-dicyano­[2,1,3]­benzothiadiazole, 5,6-dicyanobenzo­[d]­[1,2,3]­triazole, 6,7-dicyanoquinoxaline, and 6,7-dinitroquinoxaline, are shown to undergo facile palladium-catalyzed C–H direct arylation with a variety of bromoarenes in moderate to high yields. The electrochemical characteristics of di-2-thienyl derivatives synthesized using this methodology are compared and suggest that, in an electron-transfer sense, 5,6-dicyano­[2,1,3]­benzothiadiazole is a comparably strong acceptor to benzo­[1,2-c:4,5-c′]­bis­[1,2,5]­thiadiazole. The synthetic results suggest that high electron-withdrawing ability, which has traditionally limited reaction yields and structural variety in organic electronic materials, may be advantageous when employing C–H activated direct arylation in certain circumstances.