Categories: C=C Bond Formation >
Synthesis of enol ethers
An efficient Z-selective oxidative isomerization process of allyl ethers catalyzed by a cobalt(II) (salen) complex using N-fluoro-2,4,6-trimethylpyridinium trifluoromethanesulfonate (Me3NFPY•OTf) as an oxidant provides thermodynamically less stable Z-enol ethers in excellent yields with high geometric control. Diallyl ethers can also be isomerized at room temperature.
G. Huang, M. Ke, Y. Tao, F. Chen, J. Org. Chem., 2020, 85, 5321-5329.
Lithium diisopropylamide (LDA) promotes virtually quantitative conversion of allylic ethers to (Z)-propenyl ethers with very high stereoselectivity in THF at room temperature. The reaction time for the conversion increases with more sterically hindered allylic ethers.
C. Su, P. G. Williard, Org. Lett., 2010, 12, 5378-5381.
Substituted benzofurans were synthesized from their corresponding substituted 1-allyl-2-allyloxybenzenes using ruthenium-catalyzed C- and O-allyl isomerization followed by ring-closing metathesis.
W. A. L. van Otterlo, G. L. Morgans, L. G. Madeley, S. Kuzvidza, S. S. Moleele, N. Thornton, C. B. de Koning, Tetrahedron, 2005, 61, 7746-7755.