The mechanism, of the Michael reaction between 2-(et:hoxycarbonyl) cyclopentanone (2) and methyl vinyl ketone (3) catalyzed by the copper(II) salt [Cu(5-fBu-Sal)2] (1) has been investigated in toluene. The kinetics of the reaction of the catalyst 1 with the oxo ester 2 has been investigated by UV/Vis spectroscopy. It has been established that [Cu(5-tBu-Sal)2] (1) reacts with 2 in a first-order reaction, which is retarded by 5-tBu-Sal-H (6), formed in the reaction after the reversible dissociation of [Cu(5-tBu-Sal)2] to [Cu(5-tBu-Sal)]+ and 5-tBu-Sal" and the subsequent reversible deprotonation of 2 by 5-tBu-Sal-. The formation of the mixed complex [Cu(5-fBuSal)(enolate-2)'J (5) is proposed and has been characterized by cyclic voltammetry. The rate constant for the overall reaction leading to [Cu(5-tBu-Sal)(enolate-2)] (5) has been determined. The reaction of the mixed complex 5 with methyl vinyl ketone (3), investigated by cyclic voltammetry, is proposed as the rate-determining step. © 2010 Wiley-VCH Verlag GmbH & Co. KGaA.
|Journal||European Journal of Inorganic Chemistry|
|Publication status||Published - 1 Jan 2010|
- Michael addition
- Reaction mechanisms