Asymmetric 1,4-Hydrosilylations of α,β-Unsaturated Esters
Bruce H. Lipshutz,* Jeff M. Servesko and Benjamin R. Taft
*Department of Chemistry & Biochemistry, University of California, Santa
Barbara, California 93106, Email: lipshutzchem.ucsb.edu
B. H. Lipshutz, J. M. Servesko, B. R. Taft, J. Am. Chem. Soc., 2004, 126, 8352-8353.
DOI: 10.1021/ja049135l
Abstract
A complex of catalytic amounts of CuH with a nonracemic JOSIPHOS or SEGPHOS ligand leads to exceedingly efficient and highly enantioselective 1,4-reductions of α,β-disubstituted enoates and lactones using PMHS as the stoichiometric reducing agent.
see article for more examples
see article for more reactions
Details
The document discusses the development of asymmetric 1,4-hydrosilylation methods for α,β-unsaturated esters using nonracemic ligands complexed with CuH. The study, conducted by Bruce H. Lipshutz and colleagues at the University of California, Santa Barbara, highlights the use of two ligands, DTBM-SEGPHOS and JOSIPHOS, which demonstrate high facial selectivity and efficiency in these reactions. The research shows that β-substituted ethyl cinnamate derivatives can achieve high enantiomeric excess (ee) and yields using these ligands. The study also addresses the limitations with β,β-dialkyl-substituted enoates and how the JOSIPHOS ligand series can overcome these challenges. The methodology allows for high substrate-to-ligand ratios, making it operationally straightforward and generalizable. The influence of alcohol additives on reaction rates and the effect of existing stereocenters in substrates were also examined. The findings suggest that this new technology is highly effective for producing enantiomerically enriched esters and lactones, with potential applications in synthesizing complex molecular structures. The research was supported by the NSF and involved collaboration with experts from Solvias and Takasago, who provided the ligands used in the study.
Asymmetric CuH-Catalyzed 1,4-Reductions in Water at Room Temperature
S. Huang, K. R. Voigtritter, H. B. Unger, B. H. Lipshutz, Synlett, 2010, 2041-2044.
B. H. Lipshutz, J. M. Servesko, T. B. Petersen, P. P. Papa, A. A. Lover, Org. Lett., 2004, 6, 1273-1275.
Key Words
1,4-Reductions, Enones, PMHS, CuH
ID: J48-Y2004-1560