An efficient access to (Z)-beta-fluoroallyl alcohols based on the two carbon homologation of aromatic aldehydes by Horner-Wadsworth-Emmons reaction with 2-(diethoxyphosphinyl)-2-fluoro-ethanethioic acid, S-ethyl ester followed by reduction with sodium borohydride

作者：Kajjout Mohammed; Zemmouri Rajae; Eddarir Said; Rolando Christian^*

来源：Tetrahedron, 2012, 68(15): 3225-3230.

DOI：10.1016/j.tet.2012.02.039

• (Z)-beta-Fluoroallyl alcohols
• Horner-Wadsworth-Emmons
• alpha-Fluorothioesters
• NaBH4 reduction
• Fluroconiferin

We describe a biomimetic approach to (Z)-beta-fluoroallyl alcohols based on the two carbon homologation of aromatic aldehydes to alpha-fluorocinnamic thioesters by Horner-Wadsworth-Emmons reaction with 2-(diethoxyphosphinyl)-2-fluoro-ethanethioic acid, S-ethyl ester, followed by reduction with sodium borohydride in mild conditions. The alpha-fluorothioesters were obtained in a good yield by condensing the aldehydes with the lithium anion of 2-(diethoxyphosphinyl)-2-fluoro-ethanethioic acid, S-ethyl ester in THF at -78 degrees C. The (E,Z)-alpha-fluorocinnamic thioester mixtures were then cleanly reduced with double bond isomerisation to the corresponding (Z)-beta-fluoroallyl alcohols by NaBH4 at room temperature. This methodology may be applied to highly functionalized aldehydes as exemplified by the straightforward access to (Z)-beta-fluoroconiferin, a strong inhibitor of lignin polymerization from O-glucosylated vanillin.

• 出版日期2012-4-15