72301-33-8Relevant academic research and scientific papers
Facile, Temperature-Dependent Formation of Gaseous C1 and C2 Perfluoroalkyl Hypofluorites. Applications as Electrophilic Fluorinating Agents.
Mulholland, G. Keith,Ehrenkaufer, Richard E.
, p. 1482 - 1489 (2007/10/02)
A convenient method for continuous-flow production of gaseous C1 and C2 fluoroxyperfluoroalkanes (RfOF) was developed.Passage of 10percent F2 through short columns of CF3CO2Na resulted in the formation of the following hypofluorites: CF3CF2OF, CF3OF, CF3CF(OF)2, and CF2(OF)2.No other significant oxidizing side products or residual F2 were present in the column effluent under normal conditions.Identifications of the hypofluorites were made through direct 19F NMR measurements at -40 deg C of the -196 deg C condensate of the column effluent and also on the basis of stilbene trapping experiments.Hypofluorites were formed rapidly at temperatures at least as low as -110 deg C but no reaction occurred at -160 deg C.The ratios of hypofluorites formed strongly depended on the temperature of the salt column.Yields of CF3CF(OF)2 exceeding 90percent, based on input F2, were obtained at salt temperatures between -110 and -78 deg C.At moderate temperatures (-20 to +20 deg C) CF3CF2OF was the predominant products, accompanied by significant amounts of CF3OF and CF3CF(OF)2 and traces of CF2(OF)2.CF3OF was the major hypofluorite formed at high (60 to 100 deg C) temperatures.No hypofluorites were detected when the column temperature was above 135 deg C.A minimum of specialized equipment is required to produce hypofluorites by this method.It makes expensive or previously exotic, little-studied fluoroxy compounds readily available for synthetic applications.Fluorinations of anisole, 3,4,6-triacetyl-D-glucal, phenylmercuric acetate, and N,N-dimethylphenylacetamide tert-butyldimethylsilyl enolate were carried out to demonstrate the synthetic utility of RfOF and to compare its chemical reactivity with acetyl hypofluorite, an electrophilic fluorinating agent currently in wide use.RfOF, used as a homogeneous reagent, was comparable in fluorinating ability but was less regio- and stereoselective than acetyl hypofluorite in the cases examined.
Synthesis and Chemistry of Trifluoroacetyl Hypofluorite with Elemental Fluorine. A Novel Method for Synthesis of &α-Fluorohydrins
Rozen, Shlomo,Lerman, Ori
, p. 672 - 678 (2007/10/02)
Sodium trifluoroacetate reacts with fluorine in the presence of traces of water or HF to give mainly trifluoroacetyl hypofluorite, CF3COOF (1).This uncommon reagent was reacted in situ with a number of stilbenes and with diphenylacetylene.The oxygen-bound fluorine clearly acts as an electrophile, since Markownikoff addition of 1 to the double bond was observed.However, in cases where the Hammett constant ?p+ of the ring substituent is low, as in 4-chloro- (15) or 4-methyl- (32) stilbenes, some of the regioselectivity is lost.Usually only syn adducts were found except in cases where the 1-fluoro carbocation is stabilized, as in the case of trans-4-methoxystilbenes (23), or more than usual sterically hindered, as in trans-2-(carbomethoxy)stilbene (20).The stereoselectivity achieved in the reaction of 1 with stilbenes was compared with the stereoselectivity of fluoroxyperfluoroalkanes, RfOF, with the same olefins.In the light of this comparison it seems to us that the oxygen-bound fluorine in 1 is more electrophilic in character than in RfOF compounds.The reaction products of diphenylacetylene (28) with 1, which are in sharp contrast to the products of the parallel reaction of 28 with CF3OF, support this observation.The strong electrophilic character of the oxygen-bound fluorine of 1 is also demonstrated by aromatic electrophilic fluorination taking place on the activated ring of 4-methoxystilbene (23).In almost all cases the 1-fluoro-2-hydroxy (or 2-trifluoroacetoxy) compounds adopt the more stable gauche conformation as evident from their NMR (1H and 19F) spectra.In the case of steric disturbance, however, as in 21b and 22b, a deviation from the gauche conformation was observed and discussed.The 1-fluoro-2-trifluoroacetoxy compounds were readily hydrolyzed to the corresponding α-fluorohydrins, thus opening a new route for the synthesis of this important group.
