Ru(II)-NNO pincer-type complexes catalysed E-olefination of alkyl-substituted quinolines/pyrazines utilizing primary alcohols

An efficient and selective E-olefination of alkyl-substituted quinolines and pyrazines through acceptorless dehydrogenative coupling of alcohols catalysed by Ru(II)-N<^>N<^>O pincer-type complexes encompassing carbonyl and triphenylarsines as co-ligands is demonstrated. An array of Ru(II) catalysts has been synthesized and evaluated by analytical and spectral methodologies. The solid-state molecular structure of the synthesized complex (2) has been substantiated by x-ray crystallography. The catalytic protocol produces a diverse range of olefinated products up to 90% by employing readily available primary alcohols. The present synthetic strategy is operationally simple and scalable and tolerates various functional groups under mild reaction conditions. Notably, an aldehyde and aryl-2-quinoline-2-yl-ethanol intermediate are involved in the catalytic reaction mechanism. The utility of the present procedure is demonstrated through a facile synthesis of the antifungal drug (E)-2-(2-(pyridin-4-yl)vinyl)quinoline.

Automated summary

An efficient and selective E-olefination of alkyl-substituted quinolines and pyrazines was demonstrated using Ru(II)-N^N^O pincer-type complexes. A diverse range of olefinated products can be produced up to 90% yield, highlighting the operational simplicity and scalability of the synthetic strategy. The utility of the procedure was shown through the facile synthesis of an antifungal drug.