Epoxy ring-opening fluorination

The curing of an epoxy resin adj acent to an embedded silica optical fibre was monitored in situ by evanescent wave spectroscopy. The epoxy resin was partially fluorinated and had a lower refractive index than the silica fibre. The lower refractive index of the epoxy resin allowed the silica optical fibre to be used as a waveguide for the internal reflection of the near-IR light. The epoxy resin curing was determined as a function of time and temp, by analysis of the near-IR spectmm from the epoxy adj acent to the fibre obtained by the interaction of the evanescent wave that occurred at each internal reflection with the low refractive index epoxy resin. The results obtained showed that epoxy ring-opening and... 

Ring-opening fluorination of 2,3-epoxy-alcohols is one of the most important ways of introducing fluorine atoms into functionalized organic compounds (Scheme 12.12). Sc(OTf)3 could act as an efficient catalyst in ring-opening fluorination of 2,3-epoxyalcohols by ammonium hydrogen fluorides [20]. 

Chloromethyl)oxirane (3) affords 1,3-difluoro- and l-chloro-3-fluoropropan-2-ol (4 and 5) on reaction with potassium hydrogen fluoride in diethylene glycol.76 There is no reaction when potassium fluoride is used which indicates that the epoxy ring in 3 is opened by the hydrogen fluoride present in potassium hydrogen fluoride and later the chlorine is exchanged for fluorine. 

We developed a new easy and versatile diastereoselective synthesis of these amino alcohols. Our synthetic plan was based on the ring opening of trifluoromethyl epoxy ethers 3, which are easily available in two steps from the cheap ethyl trifluoroacetate, and are useful building blocks. The first step, the Wittig olefination of this ester, is possible because of the increased electrophilicity of the ester carbonyl by the fluorinated moiety (Scheme... 

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