A new route to N-aromatic heterocycles from the hydrogenation of diesters in the presence of anilines† †Electronic supplementary information (ESI) available. See DOI: 10.1039/c7sc01718a

• Published in: Chemical science (Cambridge) Vol. 8; no. 10; pp. 6911 - 6917
• Main Authors: Shi, Yiping, Kamer, Paul C. J., Cole-Hamilton, David J., Harvie, Michelle, Baxter, Emma F., Lim, Kate J. C., Pogorzelec, Peter
• Format: Journal Article
• Language: English
• Published: Royal Society of Chemistry 08.08.2017
• Subjects: Chemistry
• ISSN: 2041-6520; 2041-6539
• DOI: 10.1039/c7sc01718a

The hydrogenation of dicarboxylic acids and their esters in the presence of anilines provides a new synthesis of heterocycles. 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.