General, Robust, and Stereocomplementary Preparation of β-Ketoester Enol Tosylates as Cross-Coupling Partners Utilizing TsCl-N-Methylimidazole Agents
Hidefumi Nakatsuji, Kanako Ueno, Tomonori Misaki and Yoo Tanabe*
*Department of Chemistry, School of Science and Technology, Kwansei Gakuin University, 2-1 Gakuen, Sanda, Hyogo 669-1337, Japan, Email: tanabekwansei.ac.jp
H. Nakatsuji, K. Ueno, T. Misaki, Y. Tanabe, Org. Lett., 2008, 10, 2131-2134.
DOI: 10.1021/ol800480d (free Supporting Information)
TsCl coupled with NMI forms a highly reactive N-sulfonylammonium intermediate. β-Ketoesters undergo (E)-selective tosylation using TsCl-NMI-Et3N and (Z)-selective tosylation using TsCl-NMI-LiOH in good yield. Stereoretentive Negishi and Sonogashira couplings using enol tosylates proceed successfully to give trisubstituted α,β-unsaturated esters.
see article for more examples
H. Nakatsuji, H. Nishikado, K. Ueno, Y. Tanabe, Org. Lett., 2009, 11, 4258-4261.