The reactions of aromatic compounds with bromine trifluoride (2): Octafluoronaphthalene

The reaction of bromine trifluoride with octafluoronaphthalene has been investigated, from which was obtained decafluoro-1,2-benzocyclohexa-1,4-diene, 2-bromo-undecafluorotetralin and a mixture of dibromotetradecafluorobicylo [4,4,0] decene isomers. Dehalogenation and reduction gave decafluoro-1,2-benzocyclohexa-1,3-diene in addition to the 1,4-diene and 2$\text{H}$-undecafluorotetralin, a similar mixture being obtained from the dibromo decene. The reactions of the dienes and bromofluorotetralin with methoxide ion have also been studied.     

Some hydrogen abstraction reactions of the CF3CCl2 radical

The gas phase photolysis of CF₃CCl₃ in the presence of several alkanes has been used to obtain Arrhenius parameters for the abstraction of hydrogen atoms by the CF₃CCl₂ radical: Activation energies of 9.6 and 8.0 kcal/mole are found for abstraction from secondary and tertiary C–H bonds, respectively. The Arrhenius parameters are compared to those for CCl₃ and CF₃ radicals.     

Perhalogenmethylmercapto-heterocyclen,IX (perchlormethylmercapto)- und (perfluormethylmercapto)pyridine

Methods of substituting pyridine by perhalogenomethylmercapto groups are discussed. The side chain chlorination of 2-(methylmercapto)pyridine leads gradually to 2-(trichloromethylmercapto)pyridine hydrochloride ($\text{1a}$) and 2-(trichloromethylmercapto)pyridine ($\text{1b}$). Neither a direct reaction of pyridine with CF₃SCl nor the way over a Grignard reaction or a sulfenylcarboxylate lead to CF₃S-substituted products. Reactions of pyridine and bromopyridines with Hg(SCF₃)₂ yield 1:1-adducts ($\text{2a-d}$) only. Lithium tetrakis(1,2-dihydro-1-pyridyl)aluminate (LDPA) reacts with CF₃SCl to give 3-(trifluoromethylmercapto)pyridine ($\text{3}$); in addition a disubstituted product can be identified massspectroscopically. ¹H- and ¹⁹F-NMR-spectra are reported.     

Reactions of F-propene and its dimer with sodium dialkyldithiocarbamate

Sodium dialkyldithiocarbamates readily attacked $\text{F}$-propene to give S-(1,1,2,3,3,3-hexafluoropropyl)-N,N-dialkyldithiocarbamates, CF₃CHFCF₂SC(S)-NR₂, and $\text{Z}$ and $\text{E}$-S-(1,2,3,3,3-pentafluoropropenyl)-N,N-dialkyldithiocarbamates, CF₃CFCFSC(S)NR₂. The pyrolysis of the former compound quantitatively gave the dialkylthiocarbamoyl fluorine, R₂NC(S)F, while the latter compound and sodium tetraphenylborate formed the corresponding 1,3-dithiolan-2-ylium tetraphenylborate. $\text{F}$-2-Methyl-2-pentene also reacted with sodium dialkyldithiocarbamate to give (CF₃)₂CHC[SC(S)NR₂]CFCF₃. The mechanism of this reaction is supposed to involve a 1,4-RSF-elimination.     

Synthesis of 2-alkylthio (or trifluoromethylthio)-2-halogenoethenyl derivatives by means of wittig (under phase transfer conditions) or wittig-horner reactions. Application in the field of pyrethroids

A mixture of RSCHCl₂, Ph₃P and $\text{trans}$-caronaldehyde ethyl ester, treated with aq.NaOH under phase transfer conditions, gave the corresponding 2-alkylthio,2-chloroethenyl derivative, the product of the Wittig reaction of a phosphorane formed 'in situ'. The analogous derivative of the $\text{cis}$- and the 2-methylthio, 2-bromoethenyl derivative of the $\text{trans}$-caronaldehyde ethyl ester were synthesized also by means of Wittig-Horner reactions. The 2-trifluoromethylthio, 2-chloro-ethenyl derivative of the caronaldehyde ethyl ester ($\text{cis}$-$\text{trans}$ mixture) was also obtained through the phosphonate prepared from CF₃Cl + N₂CHP(OET)₂→ CF₃SCHClP(O)(OEt) The new derivatives prepared were converted to final pyrethroids by esterification with cyano(m-phenoxyphenyl)methanol.     

Nitroxide chemistry. Part XVII [1]. Reaction of bistrifluoromethyl nitroxide with some halogenoalkanes and related alkenes

The mono (bistrifluoromethylamino-oxy)alkanes (CF₃)₂NOCXYZ (X = Y = F, Z = Cl; X = H, Y = F or Cl, Z = CH₃; X = Y = F, Z = CH₃; X = H, Y = Cl or Br, Z = CF₃; X = Cl, Y = Br, Z = CF₃) have been synthesised by treatment of appropriate halogenoalkanes, CHXYZ, with bistrifluoromethyl nitroxide. The 1,2-bis(bistrifluoromethylamino-oxy)alkanes (CF₃)₂NOCH₂CXYON(CF₃)₂ were obtained as by-products in the reactions involving the ethanes CH₃CHXY (X = H, Y = F or Cl; X = Y = F); these products, like their analogues (CF₃)₂NOCHFCF₂ON(CF₃)₂ and (CF₃)₂NOCH₂CCl₂ON(CF₃)₂, were also prepared $\text{via}$ attack of bistrifluoromethyl nitroxide on the corresponding ethenes.     

An organocopper mediated synthesis of (E)-1,4-di-tert-butylbutatriene.

In the paper a highly stereoselestive route to $\text{trans}$-1,4-di-tert-butylbutatriene $\text{via}$-$\text{t}$-BuCu induced 1,3-substitution in ($\text{Z}$)-$\text{t}$-BuCHC(Br)CCH is described.     

The infrared carbonyl band of ethyl haloacetates and rotational isomerism

The integrated intensities of the carbonyl band components of the following ethyl haloacetates, R-COOFt (R = CH₂Cl, CH₂Br, CHCl₂ and CHBr₂), have been measured at different temperatures. From these intensities, values of ΔH° for the equilibrium between the $\text{cis}$ and $\text{gauche}$ rotamers have been estimated. Ethyl haloacetates have been studied in both CCl₄ solution and in gas phase. The absolute values of ΔH° in solution are lower than in gas phase. Results obtained in gas phase indicate that the stability of the $\text{gauche}$ rotamer increases with the size of the halogen atom.     

Some reactions of 1,2,3,4,7,7-hexafluorobicyclo[2,2,1]hepta-2,5-diene: Thermolysis and attack by methoxide ion and by bistrifluoromethyl nitroxide

1,2,3,4,7,7-Hexafluorobicyclo[2,2,1]hepta-2,5-diene gave 1,2,3,4-tetrafluorebenzene in at least 73% yield when heated to 450°C in a sealed tube; the CF₂ bridge appeared, in part, as octafluorocyclobutane. Nucleophilic attack by sodium methoxide- methanol on the diene occurred exclusively at the CFCF bond, causing the formation of 1,2,4,7,7-pentafluoro-3-methoxybicyclo- [2,2,1]hepta-2,5-diene and a 1,4,5,6,7,7-hexafluoro-5-methoxybicyclo [2,2,1]hept-2-ene thought, on the basis of ¹⁹F nmr data, to be the 6-$\text{endo}$-F,5-$\text{exo}$-MeO isomer. Radical attack on 1,2,3,- 4,7,7-hexafluorobicyclo[2,2,1]hepta-2,5-diene by bistrifluoromethyl nitroxide took place at both olefinic sites, with a $\text{ca}$. 10:1 preference for the CFCF linkage; all three geometrical isomers of 5,6-bis(bistrifluoromethylamino-oxy)-1,4,5,6,7,7- hexafluorobicyclo[2,2,1]hept-2-ene were formed.     

Polyfluorobicyclo[2, 2, 2]octanes. Part II. Syntheses of polyfluorobicyclo[2, 2, 2]oct-2-enes from polyfluoro-cyclohexa-1,3-dienes

Diels-Alder reactions between ethylene and octa-, 1$\text{H}$-hepta-, and 1H, 4H-hexa-fluorocyclohexa-1,3-diene gave, respectively, 1,2,3,4,5,5,6,6-octa-, 1,2,3,5,5,6,6-hepta-, and 2,3,5,5,6,6-hexa-fluorobicyclo[2, 2, 2]oct-2-ene, each characterised by oxidation to the corresponding polyfluorocyclohexane-1,4-dicarboxylic acid.     

The hydrolysis of bromodifluoromethyltriphenylphosphonium bromide [1]

Hydrolysis of [Ph₃$\text{P}\text{+}$CF₂Br]Br^? afforded a high yield of bromodifluoromethane and triphenylphosphine oxide. Hydrolysis in the presence of a radioactive isotope of bromine or sodium iodide gave unequivocal evidence that the mechanism for this reaction proceeds through a difluorocarbene intermediate.     

Synthesis of bromodifluoromethyl phenyl sulfide,sulfoxide and sulfone [1]

Sodium thiophenoxide reacts with dibromodifluoromethane to give bromodifluoromethyl phenyl sulfide. Peracid oxidation of the sulfide gives the corresponding sulfoxide and sulfone. The formation of the sulfide is suggested to proceed $\text{via}$ attack of thiophenoxide on halogen to produce difluorocarbene. Capture of carbene by thiophenoxide followed by a second positive halogen abstraction reaction yields the sulfide, PhSCF₂Br. The use of excess sodium thiophenoxide yields difluorobis(thiophenyl)methane, (PhS)₂CF₂, $\text{via}$ a similar mechanistic scheme.     

A 29Si, 13C and 1H NMR study of the interaction of various halotrimethylsilanes and trimethylsilyl triflate with dimethyl formamide and acetonitrile,a comment on the nucleophile induced racemisation of halosilanes

The ²⁹Si, ¹³C and ¹H NMR spectra of $\text{1}\text{1}$ mixtures of Me₃SiI and Me₃SiOSO₂CF₃ with DMF in CD₂Cl₂ show signals that are consistent with the formation of Me₃SiO$\text{C}\text{+}$H(NMe₂)X^? but not with penta- or hexa-coordinate silicon species. The spectra of a $\text{1}\text{1}$ mixture of Me₃SiBr and DMF show a rapidly exchanging, equilibrium mixture of Me₃SiO$\text{C}\text{+}$H(NMe₂)Br^? and starting materials. No strong evidence for salt formation between DMF and Me₃SiCl was obtained. The spectra of Me₃SiX (X = I, Br, Cl, OSO₂CF₃) in CD₃CN indicate that neither adduct formation nor extra coordination at silicon is significant.     

1, 4‐Additions of HCl and HBr to a Tetrasilabutadiene: Formation of Unsymmetrically Substituted Disilenes [1]

The reactions of hexakis(2,4,6‐triisopropylphenyl)tetrasilabuta‐1,3‐diene R₂Si=SiR—SiR=SiR₂ ( 1 ) with HCl and HBr, slowly generated from HSiCl₃ or LiBr and CF₃COOH, respectively, furnish the unsymmetrically substituted disilenes R₂XSi—SiR=SiR—SiHR₂, X = Cl ( 2 ), Br ( 3 ), by formal 1,4‐addition of the hydrogen halides to 1 . However, passing gaseous hydrogen halides over the solution of 1 yields the 1,4‐dihalotetrasilanes by two‐fold 1,2‐additions to the double bonds of 1 . The structures of 2 and 3 which crystallize isotypically with one another have been determined by X‐ray crystallography.     

Alicyclische verbindungen-v. darstellung diverser 1,3-butadienylcyclobutane

$\text{cis}$-($\text{3}$) and $\text{trans}$-1,3-Butadienylcyclobutane ($\text{4}$), all-$\text{trans}$-1-(1 ,3-butadieny1 )-2- vinylcyclobutane ($\text{10}$), and all-$\text{trans}$-1,2-bis(1,3-butadienyl)cyclobutane ($\text{15}$) have been prepared from readily available starting materials, and pyrolyzed to various cyclohexenes.     

Tris(acetonitrile)tricarbonylchromium(0) catalyzed 1,4-addition of hydrogen to 1,3-dienes

The Cr(CO)₃(CH₃CN)₃ complex is found to catalyze the 1,4-addition of hydrogen to 1,3-dienes such as 2-methyl-1,3-butadiene, trans-1,3-pentadiene, and trans, trans-2,4-hexadiene at low temperature (40°) and low H₂ pressure (20 psi). For trans, trans-2,4-hexadiene the only product obtained when D₂ is used is 2,5-dideuterio-cis-3-hexene. The catalytic 1,4-hydrogenation can be carried out in neat dienes, and turnover numbers for the catalyst of greater than 3000 have been observed.     

Structural information from OH stretching frequencies—conformations of cyclohexanol and cyclohexandiols

Infrared spectra of cyclohexanol and the trans and cis forms of cyclohexandiols with 1,4-, 1,3- and 1,2-OH groups in solution in CCl₄, CDCl₃ and in low temperature matrices in argon are reported for the OH stretching region. Band splittings are observed in the matrix state and the components are assigned to equatorial and axial OH groups. These are not split in spectra of solutions because of the greater band width in this state. Bands from hydrogen bonded forms are observed for favourable spatial arrangements.     

Electron transfer reactions between pentafluorobenzoyl peroxide and dimethoxybenzenes

Pentafluorobenzoyl peroxide (FBP) reacted rapidly with dimethoxybenzenes in F₁₁₃ (CCl₂FCClF₂) with kinetics of first order in each component. High yields of ring-substituted esters of $\text{m}$-dimethoxybenzene ($\text{m}$-DMB) and $\text{p}$-dimethoxybenzene ($\text{p}$-DMB) were obtained, whereas for 2,5-di-$\text{t}$-butyl-1,4-dimethoxybenzene (DBDMB), the $\text{t}$-Bu group was simultaneously eliminated. For 2,5-dimethyl-1,4-dimethoxybenzene (DMDMB), the benzylic hydrogen was substituted. Rate and product studies both indicate a rate-determining electron transfer step leading to radical ion pairs which collapse to products.     

Microstructure of 1,2-<Emphasis Type="Italic">trans</Emphasis>-and 1,4-<Emphasis Type="Italic">trans</Emphasis>-poly(penta-1,3-dienes)

Microstructures of 1,2-trans-and 1,4-trans-poly(penta-1,3-dienes) synthesized using different catalysts were determined by high resolution ¹³C NMR spectroscopy. The content of dyad combinations of the 1,4-and 1,2-structures was quantitatively determined in hydrogenated poly(penta-1,3-dienes) from the ratio of intensities of the characteristic signals of the carbon atoms of the methylene groups in the ¹³C NMR spectra. Published in Russian in Izvestiya Akademii Nauk. Seriya Khimicheskaya, No. 6, pp. 1113–1118, June, 2007.     

Conformational analysis of trans-2,3-diaryloxy-1,4-dioxanes. A tool for discriminating between steric and electronic effects in the position of

The conformation of several $\text{trans}$-2,3-diaryloxy-1,4-dioxanes has been studied using ¹H NMR techniques. $\text{Trans}$-2,3-bis(4-nitrophenoxy)-1,4-dioxane and $\text{trans}$-2,3-bis(4-methoxyphenoxy)-1,4-dioxane have been found to be predominantly ( ≈98%) in diaxial conformation in CDCl₃). On the other hand, $\text{trans}$-2,3-bis(2,6-dimethylphenoxy)-1,4-dioxane exists in the same conditions as a 66:33 mixture of diaxial and diequatorial conformers. An explanation based on the fulfilment of the exo-anomeric effect is provided.