Cycloaddition reactions of furan derivatives with trifluoroethene

The cycloaddition reaction of trifluoroethene with furan and a number of derivatives to give the unreported 1,1,2-trifluoro-7-oxa-bicyclo[2.2.1]hept-4-ene, and derivatives has been investigated. Reactions were carried out in stainless steel autoclaves at 200°C under autogenous pressure using an excess of trifluoroethene. Reactions were found to proceed with furan and derivatives with methyl groups in the 2 and/or 5 positions. Electron-withdrawing substituents in these positions prevented reaction however. Attempted dehydrofluorination of 1,1,2-trifluoro-7-oxa-bicyclo[2.2.1]hept-4-ene using a variety of bases gave no reaction, however use of LDA led to the preparation in 25% yield of 2,3-difluoro phenol.