Evidence of Cu I /Cu II Redox Process by X‐ray Absorption and EPR Spectroscopy: Direct Synthesis of Dihydrofurans from β‐Ketocarbonyl Derivatives and Olefins

• Published in: Chemistry : a European journal Vol. 21; no. 52; pp. 18925 - 18929
• 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: WEINHEIM Wiley 21.12.2015; Wiley Blackwell (John Wiley & Sons)
• Subjects: Chemistry; Chemistry, Multidisciplinary; Physical Sciences; Science & Technology; OXIDATION; CU(I); COMPLEXES; BOND FORMATION; OPERANDO IR; redox chemistry; FUNCTIONALIZATION; oxidative coupling; AMINATION; homogeneous catalysis; COUPLING REACTION; ARYL HALIDES; copper; FREE-RADICAL REACTIONS; X-ray absorption spectroscopy
• ISSN: 0947-6539; 1521-3765
• DOI: 10.1002/chem.201503822

The Cu I /Cu II and Cu I /Cu III catalytic cycles have been subject to intense debate in the field of copper‐catalyzed oxidative coupling reactions. A mechanistic study on the Cu I /Cu II redox process, by X‐ray absorption (XAS) and electron paramagnetic resonance (EPR) spectroscopies, has elucidated the reduction mechanism of Cu II to Cu I 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 Cu I has also been studied by XAS and EPR spectroscopy. This mechanistic information is applicable to the copper‐catalyzed oxidative cyclization of β‐ketocarbonyl derivatives to dihydrofurans. This protocol provides an ideal route to highly substituted dihydrofuran rings from easily available 1,3‐dicarbonyls and olefins.