Subject(s)
Decision Making , Dental Implants , Root Canal Therapy/methods , Tooth Extraction/methods , Humans , Informed Consent , Patient Care Planning , Referral and Consultation , Retreatment , Risk Assessment , Root Canal Obturation/methods , Root Canal Preparation/instrumentation , Root Canal Preparation/methods , Root Canal Therapy/instrumentation , Tooth Diseases/diagnosis , Treatment OutcomeABSTRACT
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.
