2-fluoro-2-phenylacetic acid. 4—Configuration of its esters with substituted-phenyl alcohols by 19F NMR

✍ Scribed by Michel Barrelle; Sylvain Hamman

• Book ID: 102529556
• Publisher: John Wiley and Sons
• Year: 1991
• Tongue: English
• Weight: 277 KB
• Volume: 29
• Category: Article
• ISSN: 0749-1581
• DOI: 10.1002/mrc.1260290803

✦ Synopsis

Abstract

The use of 2‐fluoro‐2‐phenylacetic acid as a chiral derivatizing agent allowed the distinction, by means of fluorine NMR spectroscopy, of enantiomers of alcohols L~1~CH(OH)L~2~ converted into the diastereoisomeric esters PhCHFCO~2~CHL~1~L~2~. The δF(RR) and δF(RS) fluorine chemical shifts of diastereoisomeric esters obtained from series of alcohols containing a substituted‐phenyl group (L~1~ or L~2~ = ZPh), and the ΔδF chemical shift differences, were linearly related to the Hammet σ parameter of Z. The ΔδF originates from the different electronic effects of L~1~ and L~2~ groups on the fluorine atom, through space, in a minor conformation. A classification of the ZPh effects on δF with respect to Ph is obtained. The configuration of substituted‐phenyl secondary alcohols, ZPhCH(OH)L, can be determined with the aid of the δF values of esters formed with PhCHFCO~2~H if the configuration of the unsubstituted alcohol PhCH(OH)L is known.