Department of Chemistry and Center for Optical Materials Science and Engineering Technologies (COMSET), Clemson University, Clemson, SC 29634, USA.
Org Biomol Chem. 2011 Jul 7;9(13):4842-9. doi: 10.1039/c1ob05041a. Epub 2011 May 6.
Nucleophilic addition-elimination of ortho- or para-substituted phenols to aryl trifluorovinyl ethers (TFVEs) in N,N-dimethylformamide was studied. Using sodium hydride as a base afforded vinyl substitution products R-Ar-O-CF=CF-O-Ar-R', where R or R' = H, Br, OMe, tert-Bu, or Ph. The vinyl substitution products produced mixtures of (Z)/(E)-isomers and this isomer ratio was influenced by substitution with more sterically encumbered phenol nucleophiles. Reactions using caesium carbonate afforded addition products R-Ar-O-CHFCF(2)-O-Ar-R' whereas upon dehydrofluorination using sodium hydride produced vinyl substitution products. The preparation of vinyl substituted and addition products proceeded in overall good isolated yields and were elucidated using (1)H and (19)F NMR, GC-MS, and X-ray analysis. Vinyl substituted products were inert to UV light and chemical reactivity using common polymerization promoters. Thermal activation of the (Z)/(E)-fluoroolefin (-CF=CF-) was observed at an onset of 310 °C in nitrogen using differential scanning calorimetry (DSC) producing insoluble network material. The synthesis, characterization, and mechanism for stereoselectivity are discussed.
邻位或对位取代酚与芳基三氟乙烯基醚（TFVE）在 N,N-二甲基甲酰胺中的亲核加成消除反应进行了研究。使用氢化钠作为碱，得到了 R-Ar-O-CF=CF-O-Ar-R'的乙烯基取代产物，其中 R 或 R'=H、Br、OMe、叔丁基或 Ph。乙烯基取代产物产生了（Z）/（E）-异构体的混合物，并且这种异构体的比例受到更具空间位阻的酚亲核试剂取代的影响。使用碳酸铯进行的反应得到了 R-Ar-O-CHFCF(2)-O-Ar-R'的加成产物，而使用氢化钠进行脱氢氟化则得到了乙烯基取代产物。乙烯基取代和加成产物的制备以总体良好的分离收率进行，并使用（1）H 和（19）F NMR、GC-MS 和 X 射线分析进行了阐明。乙烯基取代产物对使用常见聚合促进剂的紫外线光和化学反应表现出惰性。使用差示扫描量热法（DSC）在氮气中观察到（Z）/（E）-氟烯烃（-CF=CF-）的热活化在 310°C 时开始，产生不溶性网络材料。讨论了立体选择性的合成、表征和机制。
