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 . DOI: 10.1039/C7SC01718A
Copyright 2017 the authors. This article is licensed under a Creative Commons Attribution 3.0 Unported Licence. Material from this article can be used in other publications provided that the correct acknowledgement is given with the reproduced material.
The 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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