Evidence of CuI/CuII Redox Process by X-ray Absorption and EPR Spectroscopy: Direct Synthesis of Dihydrofurans from b-Ketocarbonyl Derivatives and Olefins

• Published in: Chemistry : a European journal Vol. 21; no. 52
• Main Authors: Yi, Hong, Liao, Zhixiong, Zhang, Guanghui, Zhang, Guoting, Fan, Chao, Zhang, Xu, Bunel, Emilio E., Pao, Chih-Wen, Lee, Jyh-Fu, Lei, Aiwen
• Format: Journal Article
• Language: English
• Published: United States ChemPubSoc Europe 01.01.2015
• ISSN: 1521-3765; 1521-3765
• DOI: 10.1002/chem.201503822

The CuI/CuII and CuI/CuIII catalytic cycles have been subject to intense debate in the field of copper-catalyzed oxidative coupling reactions. A mechanistic study on the CuI/CuII redox process, by X-ray absorption (XAS) and electron paramagnetic resonance (EPR) spectroscopies, has elucidated the reduction mechanism of CuII to CuI by 1,3-diketone and detailed investigation revealed that the halide ion is important for the reduction process. The oxidative nature of the thereby-formed CuI has also been studied by XAS and EPR spectroscopy. This mechanistic information is applicable to the copper-catalyzed oxidative cyclization of b-ketocarbonyl derivatives to dihydrofurans. This protocol provides an ideal route to highly substituted dihydrofuran rings from easily available 1,3-dicarbonyls and olefins. Copper