Difluoroethylene, reaction

A theoretical investigation showed that the most favourable unimolecular decomposition path of primary fluorozonide is a concerted cleavage to carbonyl oxide and formyl fluoride. The secondary fluorozonide decomposition takes place most readily in a stepwise manner initiated by the 0-0 bond rupture.153 DFT calculations have shown that ozone-difluoroethylene reactions are initiated by the formation of van der Waals complexes and then yield primary ozonides, which rapidly open to carbonyl oxide compounds. The formation of primary ozonide has been predicted to be the rate-controlling step of the oxidation process.154... 

The reaction of dihalocarbenes with isoprene yields exclusively the 1,2- (or 3,4-) addition product, eg, dichlorocarbene CI2C and isoprene react to give l,l-dichloro-2-methyl-2-vinylcyclopropane (63). The evidence for the presence of any 1,4 or much 3,4 addition is inconclusive (64). The cycloaddition reaction of l,l-dichloro-2,2-difluoroethylene to isoprene yields 1,2- and 3,4-cycloaddition products in a ratio of 5.4 1 (65). The main product is l,l-dichloro-2,2-difluoro-3-isopropenylcyclobutane, and the side product is l,l-dichloro-2,2-difluoro-3-methyl-3-vinylcyclobutane. When the dichlorocarbene is generated from CHCl plus aqueous base with a tertiary amine as a phase-transfer catalyst, the addition has a high selectivity that increases (for a series of diolefins) with a decrease in activity (66) (see Catalysis, phase-TRANSFEr). For isoprene, both mono-(l,2-) and diadducts (1,2- and 3,4-) could be obtained in various ratios depending on which amine is used. 

Ozonuies (1,2,4-trioxolanes) are generally obtained by the reaction of fluoroalkenes with ozone Thus, vmyl fluonde is oxidized to monofluoroozomde and formyl fluonde [23] (equation 15) The same ozomde is formed by ozonolysis of a mixture of cis 1,2-difluoroethylene with ethylene [24]... 

Early attempts to metalate 1,1-difluoroethylene with -butyllithium in tetra-hydrofuran or diethyl ether were unsuccessful. Another example whereby the course of the reaction may be altered by substitution of rec-butyllithium in place of n-butyllithium is the metalation of 1,1 -difluoroethylene [60] (equation 26)... 

Nonfluonnated allenes also readily react with fluoroalkenes to give diverse fluonnated alkylidenecyclobutanes [727, 12S, 129, 130] (equations 55 and 56), except for tetramelhylallene, which rearranges to 2,4-dimethyl 1,3-pentadiene under the reaction conditions prior to cycloaddition (equation 57) Systematic studies of l,l-dichloro-2,2-difluoroethylene additions to alkyl-substituted allenes establish a two-step, diradical process for alkylidenecyclobutane formation [131, 132, 133]... 

The difference in AJ for bromotrifluoroethylene and 1,1-difluoroethylene (9.78 Hz vs 1.8 Hz) may be significant. Certainly 1,1-difluoroethylene would be expected to have a much larger net dipole and, if reaction field interactions are important, to exhibit the larger effect. 

The first reactions of fluorinated olefins in CO2 reported by DeSimone et al. involved the free-radical telomerization of 1,1 -difluoroethylene and tetrafluor-oethylene.3" This work demonstrated the feasibility of carrying out free-radical reactions of highly electrophilic species in solvents other than expensive fluorocarbons and environmentally detrimental chlorofluorocarbons. The work has since been more broadly applied to the synthesis of tetrafluoroethylene-based, nonaqueous grades of fluoropolymers,such as poly(tetrafluoroethylene-co-peduoropropylvinyl ether) (Scheme 2). These reactions were typically carried out at between 20 and 40% solids in CO2 at initial pressures of between 100 and 150 bars, and 30-35°C (Table 10.1). 

Nguyen and Burton also reported a practical route to 2,2-difluorostyrenes via the palladium-catalyzed coupling of l-iodo-2,2-difluoroethylene with aryl iodides, as outlined in equation 5239. Surprisingly, F2C=CHBr does not work well in this reaction. The initially formed vinylzinc reagent undergoes a novel acid-base reaction (with unreacted olefin) and both [F2C=CHZnBr] and [F2C=CBrZnBr] are formed, as well as F2C=CH2 (Scheme 3). Thus, F2C=CFII is necessary to achieve selective formation of only the... 

Dichloro-2,2-difluoroethylene, 105 (Diethylamino)sulfur trifluoride, 110 Reduction reactions (see also Deoxygenation, Reductive. . . ) of acetals and ketals Dibromoalane, 237 Diisobutylaluminum hydride, 237 Triethylsilane-Tin(IV) chloride, 237 of acetates and other esters to alkanes Nickel boride, 197 Triphenylsilane, 334 of acyl halides to alcohols Sodium cyanoborohydride-Tin(II) chloride, 280... 

The synthesis of chlorine (I) and bromine (I) trifluoromethanesulfonates (triflates) was reported by DesMarteau. Stability and reactivity of these materials are similar to those of perfluoroalkyl hypohalites. Both compounds readily react at low temperature with a variety of fluoroolefins. Based on NMR analysis of the products of adding CF3S020X to pure cis- or trans-isomers of 1, 2-difluoroethylene, it was concluded that the reaction proceeds as syn-addition [35]. This statement was later criticized [18], since the assignment of stereoisomers was found to be incorrect. According to [18], addition of CF3S020X to haloolefins, as well as reactions of ClF, BrF and IF proceed as anti-addition via cyclic halonium cationic intermediates. 

Treatment of O-acyl esters (2) with l,l-dichloro-2,2-difluoroethylene provides a,a-difluorocarboxylic acids (37) through photolysis, followed by the hydrolysis of the adducts (36) with AgN03 (eq. 8.17) [53]. Eq. 8.18 shows the preparation of a-keto carboxylic acids (40) from carboxylic acids, by means of the radical addition to ethyl acrylate, oxidation to the sulfoxides by mCPBA, the Pummerer reaction with... 

Reaction of l-Chloro-l,2-difluoroethylene with Butyllithium and Carbon Dioxide... 

Butyllithium replaces with lithium both the hydrogen in l-chloro-1,2-difluoroethylene and the chlorine in another molecule of the same compound, in a ratio of 1 2. Subsequent treatment of the reaction mixture with carbon dioxide, water, and esterification with methanol gives a mix-... 

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