A new route to N-aromatic heterocycles from the hydrogenation of diesters in the presence of anilines
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The hydrogenation of dicarboxylic acids and their esters in the presence of anilines provides a new synthesis of heterocycles. [Ru(acac)3] and 1,1,1-tris(diphenylphosphinomethyl)ethane (triphos) gave good to excellent yields of the cyclic amines at 220 °C. When aqueous ammonia was used with dimethyl 1,6-hexadienoic acid, ε-caprolactam was obtained in good yield. A side reaction involving alkylation of the amine by methanol was suppressed by using diesters derived from longer chain and branched alcohols. Hydrogenation of optically pure diesters (dimethyl (R)-2-methylbutanedioate and dimethyl (S)-2- methylbutanedioate) with aniline afforded racemic 3-methyl-1-phenylpyrrolidine in 78 % yield.
Shi , Y , Kamer , P C J , Cole-Hamilton , D J , Harvie , M , Baxter , E F , Lim , K J C & Pogorzelec , P 2017 , ' A new route to N-aromatic heterocycles from the hydrogenation of diesters in the presence of anilines ' , Chemical Science , vol. 8 , no. 10 , pp. 6911-6917 . https://doi.org/10.1039/C7SC01718A
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DescriptionThe authors thank the EPSRC for the critical mass grant 'Clean Catalysis for Sustainable Development' (EP/J018139/1), Sasol Technology, UK for a case studentship (Y. S.) and the EPSRC UK National Mass Spectrometry Facility at Swansea University for mass spectrometric analysis.
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