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A single-flask synthesis of α-alkylidene and α-benzylidene lactones from ethoxyacetylene, epoxides/oxetanes, and carbonyl compounds
- Ng, Kevin, Tran, Vincent, Minehan, Thomas
- Tetrahedron letters 2016 v.57 pp. 415-419
- aldehydes, ambient temperature, carbonyl compounds, chemical bonding, chemical reactions, chemical structure, epoxides, lactones
- Low temperature treatment of (ethoxyethynyl)lithium with epoxides or oxetanes in the presence of BF3·OEt2, followed by addition of aldehydes or ketones and warming to room temperature, affords structurally diverse five- and six-membered α-alkylidene and α-benzylidene lactones (5) in good to excellent yields. This one-pot process, in which three new carbon–carbon bonds and a ring are formed, affords substituted α,β-unsaturated lactones of predominantly Z-configuration. The reaction likely occurs via alkyne–carbonyl metathesis of a hydroxy–ynol ether intermediate, acid-promoted alkene E- to Z-isomerization, and lactonization.