Iron-Catalyzed, Hydrogen-Mediated Reductive Cyclization of 1,6-Enynes and Diynes: Evidence for Bis(imino)pyridine Ligand Participation

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• 作者：Kevin T. Sylvester ; Paul J. Chirik
• 刊名：Journal of the American Chemical Society
• 出版年：2009
• 出版时间：July 1, 2009
• 年：2009
• 卷：131
• 期：25
• 页码：8772-8774
• 全文大小：187K
• 年卷期：v.131,no.25(July 1, 2009)
• ISSN：1520-5126

文摘

The bis(imino)pyridine iron dinitrogen complex (^iPrPDI)Fe(N₂)₂ catalyzes the hydrogen-mediated reductive cyclization of enynes and diynes with turnover frequencies comparable to those of established precious metal catalysts. Amino, oxygenated, and carbon-based substrates are readily cyclized to the corresponding hetero- and carbocycles with 5 mol % iron and 4 atm H₂ at 23 °C. Stoichiometric reactions between selected substrates and the iron compound under a N₂ atmosphere established transfer dehydrogenation from an isopropyl aryl substituent to either the enyne or diyne substrate. In situ monitoring of the catalytic reaction by ¹H NMR spectroscopy coupled with deuterium labeling experiments established rapid cyclization followed by turnover-limiting hydrogenation.