An Unusual Chemoselective Hydrogenation of Quinoline Compounds Using Supported Gold Catalysts

• Published in: Journal of the American Chemical Society 2012-10, Vol.134 (42), p.17592-17598
• Main Authors: Ren, Dong, He, Lin, Yu, Lei, Ding, Ran-Sheng, Liu, Yong-Mei, Cao, Yong, He, He-Yong, Fan, Kang-Nian
• Format: Article
• Language: English
• Subjects: Catalysis; Gold - chemistry; Hydrogen - chemistry; Hydrogenation; Metal Nanoparticles - chemistry; Molecular Structure; Quinolines - chemical synthesis; Quinolines - chemistry; Titanium - chemistry
• ISSN: 0002-7863; 1520-5126
• DOI: 10.1021/ja3066978

The pursuit of modern sustainable chemistry has stimulated the development of innovative catalytic processes that enable chemical transformations to be performed under mild and clean conditions with high efficiency. Herein, we report that gold nanoparticles supported on TiO2 catalyze the chemoselective hydrogenation of functionalized quinolines with H2 under mild reaction conditions. Our results point toward an unexpected role for quinolines in gold-mediated hydrogenation reactions, namely that of promoter; this is in stark contrast to what prevails in the traditional noble metal Pd-, Pt-, and Ru-based catalyst systems, in which quinolines and their derivatives typically act as poisons. As a result of the remarkable promotional effect of quinoline molecules to H2 activation over supported gold, the transformation can proceed smoothly under very mild conditions (even at temperatures as low as 25 °C). Of practical significance is that various synthetically useful functional groups including halogens, ketone, and olefin remain intact during the hydrogenation of quinolines. Moreover, the protocol also shows promise for the regiospecific hydrogenation of the heterocyclic ring of a variety of other biologically important heteroaromatic nitrogen compounds, such as isoquinoline, acridine, and 7,8-benzoquinoline, in a facile manner. Apart from its importance in catalytic hydrogenation, we believe that this intriguing self-promoted effect by reactant molecules may have fundamental implications for the broad field of gold catalysis and form the basis for development of new catalytic procedures for other key transformations.