E. I. Mysov

Thermal reactions of hexafluoro-1,3-butadiene. Part I. Primary products and their thermal transformations

Abstract Depending on the temperature, the thermal reactions of hexafluoro-1,3-butadiene include intra- and/or intermolecular cycloaddition and give hexafluorocyclobutene, [2+4]- and [2+2]-cycloadducts as primary products. The latter react with hexafluorobutadiene to give its trimers while the [2+2]-cycloadduct, being generated as two isomers, undergoes some thermal rearrangements in addition. Thus, cis-perfluorodivinylcyclobutane is isomerized at 150 °C to perfluorotricyclo[4.2.0.02,5]- and -[3.3.0.02,6]octanes together with unstable, easily polymerized, cis,trans-perfluoro-1,5-cyclo-octadiene. The trans isomer is isomerized at 200 °C to perfluorovinyl-4-cyclohexene and perfluorotricyclo[3.3.0.02,6]octane. Possible schemes for the formation of the latter are discussed. Racemic trans,trans-perfluoro-1,5-cyclo-octadiene is argued to be a precursor of perfluorotricyclo[3.3.0.02,6]octane in the isomerizations of both the cis- and trans-[2+2]-cycloadducts.

Electrocarboxylation of α,ω-dihaloperfluoroalkanes and of perfluoroalkylhalides in a near-critical and supercritical CO2-methanol medium

Abstract The electrocatalytical carboxylations of some perfluoroalkylhalides and α,ω-dihaloperfluoroalkanes on copper and stainless steel electrodes in near-and supercritical CO2-methanol mixtures have been investigated. The main products and intermediates were determined. It was shown that the differences in the composition of products in these two cases indicate quite different catalytic activities of copper and stainless steel electrodes with regard to the electroreduction reactions of the intermediates and quite different adsorptions of these intermediates on the surfaces of the electrodes.

Radical cyclization of allyl α-bromocarboxylates into λ-butyrolactones. Effect of the ester structure on the cyclization

Allyl dibromoacetate, allyl α-bromopropionate, and allyl phenylbromoacetate undergo cyclization in benzene in the presence of increased concentration of Fe(CO)5—DMF as the initiating system to give the corresponding bromo-substituted butyrolactones.

Thermal reactions of hexafluoro-l,3-butadiene. Part II. Synthesis and thermal transformations of C12F18 trimers

Abstract Hexafluoro-1,3-butadiene reacts at ≥ 150 °C with its cyclodimers containing trifluorovinyl groups to give all the trimers expected for [2+2]- and [2+4]-cycloadditions. The ratios of the products formed depend on the temperature and are determined by the stabilities of the dimers and trimers concerned. All those trimers which contain a cyclobutane moiety take part in thermal transformations, such as ring expansion, dimerization and retrocycloaddition reactions. Hexafluoro-1,3-butadiene and its dimers, which are formed in retrocycloaddition reactions, undergo secondary thermal transformations. The latter include the previously unknown insertion of a hexafluorobutadiene molecule into the four-membered ring of one of the dimers.

Electrophilic isomerization of fluoroaliphatic oxygen-containing compounds

An unusual electrophilic cyclization of fluorine-containing carbonyl compounds and α-oxides was discovered. Upon the action of SbF5, perfluorinated ketones, diketones, and α-oxides isomerize to oxolanes. This reaction proceeds with the obligatory participation of the terminal CF3 group.

Condensation of fluorinated carbonyl compounds with halobenzenes

Abstract Fluoro- or chlorobenzenes undergo the Friedel-Crafts acylation with perfluoroacyl chlorides ( I ) without complications to give p -halophenylketones ( II ); however, the reaction of I with bromobenzene gives phenylketones ( IV ) and dibromobenzene in addition to p -bromophenylketones ( III ). An intermediate p -bromobenzyl cation ( V ) is assumed to be responsible for the formation of the abnormal products IV and dibromobenzene. Condensation of hexafluoroacetone with bromobenzene in anhydrous HF also affords the products of disproportionation probably via an intermediate benzyl cation ( IX ).

Do fluorine atoms attached to sp2-hybridized carbon atoms hinder electrophilic addition to the CC bond?

Abstract Interaction of mercuric trifluoroacetate with 2,3-difluorobicyclo[2.2.1]hepta-2,5-diene ( I ) in a non-polar medium leads to adduct IIa , formed as a result of exo—cis -addition of the salt to the FCCF bonds of two diene molecules. Under the action of mercuric acetate in acetic acid, diene I gives an exo—cis -adduct to the FCCF bond ( IIb ) as well as one to the HCCH ( IIc ) in a 3:2 ratio. Adduct IIb reacts with excess Hg(OCOCH 3 ) 2 and isomerizes to the tricyclic exo,exo -adduct IId . Diene IV , i.e. 2,3-difluoro-1,4,4a,5,8,8a-hexahydro-1,4,5,8-dimethanonaphthalene, reacts with anhydrous CF 3 COOH adding two molecules of the acid non-stereospecifically to both double bonds, and giving a mixture of isomeric bis-adducts V . A mixture of the monoadducts to the FCCF and HCCH bonds is formed in a 1:1.7 ratio when IV interacts with CF 3 COOH in CH 2 Cl 2 . It is notable that addition to the FCCF bond leads to the exo -trifluoroacetate VIa whereas reaction with the HCCH bond gives a mixture of exo - and endo -trifluoroacetate, VIb and VIc . The relative activities of the double bonds in I and IV are discussed.

Functionalization of alkenes by polyfluorinated α,β-unsaturated sulfenyl chlorides: reactions of 2-chloroperfluoro-1-cyclohexenesulfenyl chloride-1 with activated olefins

Abstract A variety of β-chlorothioethers have been obtained by the reaction of 2-chloroperfluoro-1-cyclohexenesulfenyl chloride-1 ( I ) with t-butylethene, styrene, allylbenzene and p -methoxyallylbenzene in CH 2 Cl 2 or CH 3 NO 2 . Skeletal rearrangement with 1,2-migration of the p -methoxyphenyl group occurs on reaction of I with p -methoxyallylbenzene along with the formation of addition products (Markovnikov and anti-Markovnikov adducts). A possible additive salt effect (LiCIO 4 /CH 3 NO 2 system) has been examined for the reaction of I with t-butylethene, allylbenzene and p -methoxyallylbenzene; the effect is noted only in the case of t-butylethene, when intramolecular rearrangement with 1,2-migration of the methyl group takes place.

?,?-unsaturated fluorine-containing thiocyanates

A new method has been developed for the synthesis of perfluorinatedα,β-unsaturated thiocyanates by the reaction of the corresponding sulfenyl chlorides with KCN in water. The thiocyanate form of perfluoro-2-methyl-2-pentene-3-thiocyanate was isomerized to the isothiocyanate form. This rearrangement is initiated by both fluoride and thiocyanate anions.

Perfluorocarboxylic acid anhydrides and halides in the Wittig reaction

Conclusions1.Perfluorocarboxylic acid anhydrides and halides undergo the Wittig reaction with stable phosphorus ylides that do not contain anα-hydrogen atom.2.In contrast to other carbonyl compounds, perfluorocarboxylic acid anhydrides and halides undergo the Wittig reaction with hexafluoroisopropylidenetriethoxyphosphorane.