Cycloalkenes fluoro

The Claisen ester enolate reaction has proved to be extremely useful in the synthesis of a large number of natural products.3 In addition, the rearrangement has been extended to allow the preparation of useful intermediates such as a-alkoxy esters,88 329 33 336 343 a-phenylthio esters,339344-345 a- and [3-amino acids,340 346-350 a-fluoro esters,351 cycloalkenes,352353 tetronic acids,354 and dihydro-pyrans.355-357... 

Examples of nitrofluorination reactions of alkenes, cycloalkenes, halogenated and other substituted alkenes are shown in Tables 28 and 29. It should be mentioned that the yield of the fluoro nitro product is higher if the starting alkene is substituted by electron-withdrawing substituents. 

The formal electrophilic addition of BrF" to a double bond proceeds stereospecifically in an anti-sense as evidenced by the formation in high yields of trans-1 -bromo-2-fluorocycloalkanes from cis-cycloalkenes or of cis-1-bromo-2-fluorocyclododecane from trans-cyclododecene, respectively.5 The addition is regioselective with the observed regiochemistry being in accordance with the Markovnikov rule. For example, the bromofluorinations of a-substituted styrenes give the 1-bromo-2-fluoro-2-phenylalkanes with virtually complete regioselectivity only traces (<1%) of the regioisomeric adducts were detectable by 19F NMR spectroscopy... 

The conformational free energy difference between the equatorial and axial forms of 4-chloro-l,l-difluorocyclohexane has been measured,and CIDNP effects have been observed in the decomposition of bis-(4H-decafluoro-bicyclo [2.2.1 ]heptane-l-carbonyl) peroxide. A study oftheF-19NMR data of 38 fluoro-steroids (ketones, alcohols, and acetates) showed that the disposition of various substituents can be deduced from the F-19 chemical shift and magnitude of the geminal and vicinal J(FH) values. Other studies have been made of 1,2-difluorocyclohexane and of the free radical additions of methanol and acetaldehyde to perfluorinated cycloalkenes. °... 

NaF-AljOs yields 2-(trifluorovinyl)pyridine, which can be copolymerized with tetrafluoroethylene to yield a material possessing good receptivity towards dyes and pigments. Eliminations also feature in studies concerned with pyrolyses of the alkanes CHFj-CHFj (—HF shock tube), MeCF, (—HF shock tube, - flow over hot AIF3, FeFj, or MgFj ), MeCHF (—HF shock tube, static ), CH F CHaF (—HF flow over hot C dosed with activators), CHjF-CHjCl -HF, — HCl shock tube and static ), and CFj-CHjCI (—HF, —HCl shock tube), the synthesis of 1-fluoro-cycloalkenes (Scheme 8), a comparison of KOH dehydrofluorinations of... 

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