Ryan Nouch
Mechanistic-Insight-Driven Rate Enhancement of Asymmetric Copper-Catalyzed 1,4-Addition of Dialkylzinc Reagents to Enones
Nouch, Ryan; Woodward, Simon; Willcox, Darren; Robinson, David; Lewis, William
Authors
SIMON WOODWARD simon.woodward@nottingham.ac.uk
Professor of Synthetic Organic Chemistry
Darren Willcox
David Robinson
William Lewis
Abstract
Combination of [Cu(MeCN)4]TFA•TFAH (TFA = O2CCF3) with Feringa's phosphoramidite ligand (LA) provides an exceptionally active (0.75 mol%) catalyst for asymmetric conjugate additions of ZnR2 (R = Et, Me at-40 to-80 o C) to enones. Kinetic and other studies of the addition of ZnEt2 to cyclohex-2-en-1-one indicate a transition state stoichiometry composition: (ZnEt2)3(enone)4Cu2(LA)3 that is generated by transmetalation from Et2Zn(enone)2. Catalyst genesis is significantly slower than turnover (which has limited previous attempts to attain useful kinetic data); in the initial stages varying populations of catalytically inactive, off-cycle, species are present. These issues are overcome by a double-dosing kinetic analysis protocol. A rest state of [LACu(Et)(µ-TFA)(µ-{(enone)(ZnEt)2(enolate)})CuLA2] + (through the equivalence of enolate = enone + ZnEt2) is supported by DFT studies (B3LYP/6-31G*). Rate determining ZnEt2(enone)2 transmetalation
drives the exceptionally high catalytic activity of this system.
Citation
Nouch, R., Woodward, S., Willcox, D., Robinson, D., & Lewis, W. (2020). Mechanistic-Insight-Driven Rate Enhancement of Asymmetric Copper-Catalyzed 1,4-Addition of Dialkylzinc Reagents to Enones. Organometallics, 39(6), 834-840. https://doi.org/10.1021/acs.organomet.0c00005
Journal Article Type | Article |
---|---|
Acceptance Date | Feb 20, 2020 |
Online Publication Date | Mar 3, 2020 |
Publication Date | Mar 23, 2020 |
Deposit Date | Mar 3, 2020 |
Publicly Available Date | Mar 29, 2024 |
Journal | Organometallics |
Print ISSN | 0276-7333 |
Electronic ISSN | 1520-6041 |
Publisher | American Chemical Society |
Peer Reviewed | Peer Reviewed |
Volume | 39 |
Issue | 6 |
Pages | 834-840 |
DOI | https://doi.org/10.1021/acs.organomet.0c00005 |
Keywords | Inorganic Chemistry; Organic Chemistry; Physical and Theoretical Chemistry |
Public URL | https://nottingham-repository.worktribe.com/output/4082308 |
Publisher URL | https://pubs.acs.org/doi/abs/10.1021/acs.organomet.0c00005 |
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