Eosin Y-mediated visible light photoredox catalysis for C(2)–H arylation of quinoline N-oxides using arenediazonium salts

Abstract

2-Arylquinolines constitute a special class of compounds due to their importance in medicinal chemistry and functional materials. Quinoline N-oxides present readily available substrates that can be conveniently arylated without the need for pre-halogenated quinolines, the common precursors for cross-coupling reaction-mediated arylations. Photoredox catalysis utilizing organic dyes offers an effective tool for the greener arylations using arenediazonium salts. C-2 arylation of quinoline N-oxides was achieved by the eosin-Y mediated photoredox catalysis under green light. Reactions using 1 mol% catalyst loading provided 2-arylquinoline N-oxides in moderate to good yields. Reactions proceeded well with both commercially available arene diazonium salts and in situ generated diazonium salts from anilines. This approach is effective for a wide variety of arene- and heteroarene diazonium salts. Several electron rich and electron deficient quinoline N-oxide moieties reacted efficiently. The addition of Cs₂CO₃ proved beneficial and a significant improvement in the reaction yields could be achieved.