| Article ID | Journal | Published Year | Pages | File Type |
|---|---|---|---|---|
| 1314144 | Journal of Fluorine Chemistry | 2011 | 9 Pages |
Fluorinated norbornenes are very desirable monomers in the semiconductor and high-temperature polyimide industries. We describe herein a synthetic strategy for the stereospecific mono- or difluorination of the C7-carbon in norbornene systems beginning with 7-ketonadic anhydride 1. In particular, anti-7-fluoro methyl diester 4 and its 7,7-difluoronadic analog 7 can be prepared from 1 in 3 or 4 steps: saponification, reduction (for 4), esterification, fluorination with DAST. In addition, anti-7-fluoro-syn-7-fluoromethylnadic diester 16 is obtained from epoxide 14, and dimethyl 7,7-difluorobicyclo[2.2.2]oct-5-ene-2,3-dicarboxylate (17) from ketone 15. Anchimeric assistance of the norbornene double bond guides the introduction of attacking fluoride anions stereospecifically anti to the olefinic linkage.
Graphical abstractA synthetic strategy for the stereospecific mono- or difluorination of the C7-carbon in norbornene systems by beginning with 7-ketonadic anhydride is described.Figure optionsDownload full-size imageDownload as PowerPoint slideHighlights► C7-fluorination of norbornenes can be effected beginning with 7-ketonadic analogs. ► DAST fluorination of the 7-ketonadic analogs generate 7,7-difluoro derivatives. ► Reduction of 7-keto to 7-alcohol followed by DAST yields 7-fluoro derivatives. ► Both 7-syn and 7-anti alcohol react with DAST giving the same 7-anti fluoride. ► Anchimeric assistance guides fluorination stereoselectively anti to the double bond.
