Fluorinations with complex metal fluorides. Part 7. Fluorinations of the methyl pyridines with caesium tetrafluorocobaltate

4-Methylpyridine passed over caesium tetrafluorocobaltate at 330 – 340° gave tridecafluoro(1,3-dimethylpyrrolidine) (1) and its 3-difluoromethyl analogue (2), together with a range of polyfluoro-4-picolines (4 – 10) with ?CF₃, ?CHF₂ or ?CH₂F groups in the 4-position. 3-Methylpyridine similarly gave 1 and its 1,2-isomer (11) together with several polyfluoro-3-picolines (14 – 18). 2-Methylpyridine at 270° gave tridecafluoro(1-ethylpyrrolidine) (13), a trace of 11 and 2-trifluoromethyl- (22), 2-difluoromethyl- (23) and 2-fluoromethyl-tetrafluoropyridine (24); there were also products arising by loss of methyl. Other unidentified fluoroalkylpyridines besides those isolated were present in each case.     

Fluorinations with complex metal fluorides Part 8. Ring rearrangement in the fluorinations of quinoline with caesium tetrafluorocobaltate and with cobalt(III) fluoride

Fluorination of quinoline by caesium tetrafluorocobaltate at ca. 350° afforded mainly a mixture of pentadecafluoro-2-azabicyclo[4,4,0]dec-1(2)- ene (E), and heptadecafluoro-1-azabicyclo[5,3,0]decane (F), arising by skeletal rearrangement. Minor products were six polyfluorocyclohexa[b]- pyridines (G–L) all with carbocyclic rings having the -(CF₂)4 - moiety. Compound F was unreactive, but E was highly susceptible to nucleophiles, e.g. water and methanol. Isoquinoline was fluorinated similarly, but the only new product isolated was tridecafluoro-3-azabicyclo[4,4,0]deca- 1(6)-2-diene (R). The rearrangement occurring with quinoline prompted a re-examination of its fluorination by cobalt(III) fluoride. At ca. 350°, compound F was the major product, with very little E: there were some ring-opened materials, the most important being tetradecafluoro-4-pentafluoroethyl- 2-azaoct-2(Z)-ene (N).     

Fluorinations with potassium tetrafluorocobaltate(III) Part VII. Further investigations on the fluorination of pyridine

The product from the fluorination of pyridine by KCoF₄ at ca. 220° contains eleven fluoropyridines, two fluoro-2-azahex-enes, three azahexa- dienes, and two fluoro-N-methylpyrrolidines, besides an azacyclohexa-1,3- diene. Four products were isolated from a fluorination of pyridine by CoF₃ at ca. 150°, a 2-azahexene, two N-methylpyrrolidines, and 4H-nona- fluoropiperidine.     

Fluorinations with potassium tetrafluorocobaltate [III]. Part VIII fluorinations of toluene and of phenylacetic acid

At 340 °C, toluene gave five 1-trifluoromethyl-substituted compounds:- -2H,4H,5H-tetrafluorocyclohexa-1,4-diene (IX); -2H-4H/5H-hexafluorocyclohex-1-ene (X); -2H-octafluorocyclohex-1-ene (IV); -nonafluorocyclohex-1-ene (III); also perfluoromethylcyclohexane (II); traces of perfluorocyclohexane (I) were found. The 1-difluoromethyl-substituted analogues of these five were also obtained:- compounds XII, XV, VIII, VI, and V, respectively. A further five 1-difluoromethyl-substituted derivatives were found:- -nonafluorocyclohex-3-ene (VII); an inseparable mixture of the -2H,4H- and -2H, 5H-heptafluorocyclohex-1-enes (XI); -2H-3H/4H-hexafluorocyclohex-1-ene (probably) (XIV); and (difluoromethyl)benzene (XIII).Structures of the unknown products were established by analysis and by nmr and ir spectroscopy. Further, the key intermediate (XII) was oxidized to difluoromalonic acid, whilst compound XV was dehydrofluorinated, to give 2H-(difluoromethyl)tetrafluorobenzene (XXI), together with an inseparable mixture of 2H,4H- and 2H,5H-1-(difluoromethyl)pentafluorocyclohexa-1,4-diene (XX). Dehydrofluorination of mixed heptafluoro-enes XI afforded 2H -1-(difluoromethyl)hexafluorocyclohexa-1,4-diene (XVIII), and mixed 2H-1- and 1H -2- (difluoromethyl)hexafluorocyclohexa-1,3-diene (XIX).Difluoromethylundecafluorocyclohexane (V) did not dehydrofluorinate.Phenylacetic acid was fluorinated likewise, and gave a similar range of products, but also one (originally an acid fluoride ?) which was converted to the methyl ester of tridecafluoro(cyclohexylacetic) acid (XVII).The probable pathway of the fluorination process could be worked out.     

The fluorination of methane and related compounds by copper(II) fluoride and other metal fluorides

Methane reacted with MnF₃ between 350-650°C affording hydrogen fluoride, MnF₂, the fluoromethanes CH₃F, CH₂F₂, CHF₃ and CF₄ and a complex mixture of less volatile fluorocarbons.Methane reacted with FeF₃ between 650-950°C giving the fluoromethenes CH₃F, CH₂F₂ and CHF₃, C₂H₄ and carbon, as well as hydrogen fluoride and FeF₂.A more detailed study of the CuF₂-CH₄ reaction between 600-850°C showed that copper metal, hydrogen fluoride and CH₃F were always obtained, other products including CH₂F₂, CHF₃, CF₄, C₂H₄, C₂H₆, C₂F₆ and carbon. Yields of the fluoromethanes were enhanced by using relatively large amount of CuF₂ and by adding CaF₂ as an inert support. A nearly constant reaction rate occurred at a fixed temperature. Dilution of methane with nitrogen decreased yields of carbon and CH₃F but increased yields of C₂H₄ and C₂H₆.A brief study of the reactions with CuF₂ and some of the CH₄-CuF₂ reaction products was also made. Ethane and ethene both afforded traces of trifluoromethane and relatively large yields of carbon and hydrogen fluoride. That the fluorination of methane to tetrafluoromethane could take place sequentially was demonstrated by reactions with CH₃F, CH₂F₂ and CHF₃. Some pyrolysis of CH₂F₂ and CHF₃ also occurred under the chosen reaction conditions.The CH₄-CuF₂ reaction was made part of a cyclic process in which generation of the CuF₂ in situ from copper metal by successive reaction with oxygen at 400°C and hydrogen fluoride at temperatures rising to 600°C was followed by reaction with methane; 68% coversion to fluorinated products occurred. The cycle was completed by re-conversion of the copper metal residue back to CuF₂ and further reaction with methane when almost identical yields of fluorocarbons and hydrogen fluoride were obtained.     

The fluorination of 1,3-Bis-(trifluoromethyl)benzene over potassium tetrafluorocobaltate(III)

1,3-Bis-(trifluoromethyl)benzene has been fluorinated over potassium tetrafluorocobaltate under conditions where the bulk of the products are lightly fluorinated. Two aromatic products, 1-fluoro-2,4-bis-(trifluoromethyl)benzene and 1-fluoro-3,5-bis-(trifluoromethyl)benzene, are formed initially, the two associated 1,4-dienes being also found. The mechanistical implications are discussed, along with probable further reaction pathways.     

The fluorination of ethane and ethene over potassium tetrafluorocobaltate(III) and cobalt trifluoride

Fluorination of ethane and ethene with KCoF₄ and CoF₃ over a range of temperatures gave, in all cases, mixtures of polyfluoroethanes, C₂H_6-nF_n n = 1–6, with very little CC bond cleavage. Apart from an initial easy saturation of ethene to CH₂FCH₂F, both substrates had a similar reactivity. Hydrogen appeared to be replaced by fluorine almost randomly in all fluorinations. CH₂FCH₂F is a stable compound, contrary to literature reports.     

Synthesis of perfluorochemicals for use as blood substitutes. Part III. [1] electrochemical fluorination of quinolozidine, 4-methylquinolizidines and 4-trifluoromethylquinolizidines [2]

Electrochemical fluorination of quinolizidine gave F-quinolizidine in 16-23% isolated yields. 4-Methylquinolizidine was also fluorinated electrochemically to give the corresponding amine stereoisomers along with their fragmented and rearranged products in isolated yields of 28-34% and 2-3%, respectively. Introduction of an F-methyl group into the quinolizidine in place of the methyl group prior to electrochemical fluorination did not stabilize the 4-methyl quinolizidine structure and rather allowed the formation of F-quinolizidine to a greater extent. Oxidation of 4-(F-methyl)-F-quinolizidine with fuming sulfuric acid in the presence of a catalytic amount of HgSO₄ gave 6-oxo-4-(F-methyl)-F-quinolizidine in 60% yield, the F-nmr spectra of which gave further support to the structure of the starting material. The physical and spectral properties of these F-chemicals are described.     

The interaction of group III metal alkyls with crown ethers. The synthesis and structure of [Ga(CH3)3]2[dibenzo18-crown-6] and [Al(CH3)3]2[dicyclohexano-18-crown-6]

[Ga(CH₃)₃]₂[dibenzo-18-crown-6] and [Al(CH₃)₃]₂[dicyclohexyl-18-crown-6] were prepared by the reaction of Ga(CH₃)₃ or Al(CH₃)₃ with the appropriate crown ether in toluene. After filtering and cooling, both products were obtained as colorless, air-sensitive, rectangular crystals. The structures of both compounds were determined from single crystal X-ray diffraction data collected on a CAD-4 diffractomer. [Ga(CH₃)₃]₂[dibenzo-18-crown-6] belongs to the monoclinic space group P2₁/c with unit cell parameters a 11.460(5), b 18.000(7), c 7.495(4) Å, β 105.65(4)°, and ϱ(calc) 1.32 g cm⁻³ for Z  2. Least-squares refinement gave a final R value of 0.061 for 1179 independent observed reflections. The molecule resides on a crystallographic center of inversion. The Ga-O distance of 2.198(8) Å is among the longest yet observed. In order to accommodate the two trialkygallium units, the crown ether is forced to adopt a chair configuration. [Al(CH₃)₃]₂[dicyclohexano-18-crown-6] crystallizes in the space group P2₁/a with cell parameters a 16.423(7), b 9.812(5), c 20.935(8) Å, β 107.41(5)°, and ϱ(calc) 1.07 g cm⁻³ for Z  4. Least-squares refinement gave a final R value of 0.079. The flexibility of the crown ether in this case allows the bonded oxygen atoms to be positioned on the outside of the crown, with all six oxygen atoms in a near-planar arrangement.     

The fluorination of uranium and vanadium oxides with some metal fluorides

UO₃ reacts with CrF₃ or CuF₂ forming UO₂F₂ and Cr₂O₃ or CuO respectively. Further fluorination occurs above 800°C to form UF₆ though the presence of excess CrF₃ gives mainly UF₄. The fluorination of U₃O₈ with CrF₃ gave UO₂F₂, UF₄ and Cr₂O₃ but with CuF₂ gave UO₂F₂, CuO and Cu₂O. VO₂ reacts with excess CrF₃ forming VF₃, VF₅ and Cr₂O₃. If there is a deficiency of CrF₃ the products are VOF₃, V₃O₅ and Cr₂O₃. CuF₂ and VO₂ form VOF₃, CuO and Cu₂O.     

Double complex salts [Ni(NH3)6]3[Fe(CN)6]2 and [Ni(NH3)6]3[Cr(CNS)6]2: Synthesis and properties

The double complex salts [Ni(NH₃)₆]₃[Fe(CN)₆]₂ and [Ni(NH₃)₆]₃[Cr(CNS)₆]₂ were synthesized and their thermal decomposition in air was studied. The values of interplanar distances in crystal lattices were determined. The compounds are proposed as precursors for producing homogeneous bimetallic nanodimensional powders.     

Crystal structure of a La(III) complex with macrocyclic cavitand cucurbit[6]uril

Slow evaporation in air of a lanthanum nitrate solution containing macrocyclic cavitand cucurbit[6]uril yields a complex of the composition of [La(H₂O)₆(X@C₃₆H₃₆N₂₄O₁₂)(NO₃)](NO₃)₂· 6.96H₂O (X = 0.5C₅H₅N + 0.5H₂O). The complex is structurally characterized using single crystal X-ray diffraction. Lanthanum atoms are coordinated with oxygen atoms of carbonyl groups of cucurbit[6]uril portals. The compound crystallizes in the orthorhombic crystal system, space group Pnn2, unit cell parameters (150 K): a = 11.997(2) Å, b = 17.093(3) Å, c = 14.133(3) Å, V = 2899.3(10) ų, Z = 2. Lanthanum atoms are disordered, alternative positions being related by the two-fold axis. The complex has an island structure. A pyridine molecule occupies an internal cavity of one half of cucurbit[6]uril molecules, while a water molecule occupies the other.     

F-alkyliron(II) compounds[1]

F-Alkyliron tetracarbonyl iodides are convenient sources of terminal vinyl iodides by a simple pyrolytic technique. The precursors to the F-alkyliron tetracarbonyl iodides, an F-alkyl iodide and iron pentacarbonyl, can be used to generate F-alkyl radicals capable, for example, of F-alkylating benzene in moderate yield. Mechanisms for these transformations are proposed.     

Polyhalogenoheterocyclic compounds. Part 37 [1]. Perfluorotetrahydro-quinoline, -isoquinoline,and related compounds

The formation of perfluorotetrahydro-quinoline (3) and -isoquinoline (6) in the high temperature reaction between KF and heptachloro-quinoline and -isoquinoline is investigated and a mechanism is proposed. Compounds (3) and (6) represent unusually substituted pyridine derivatives and the orientation of substitution in reactions with nucleophiles is reported.     

Cyclic aryleneazachalcogenenes. Part III [1] synthesis of polyfluorinated 2,1,3-benzothia-(selena) diazoles

1-(4-X-Tetrafluorophenyl)-3-trimethylsilyl-1,3-diaza-2- thiaallenes (X = H, CH₃, Br, F, CF₃) treated with CsF in acetonitrile or THF cyclized to 6-X-4,5,7-trifluoro-2,1,3-benzothiadiazoles whose reduction led to the corresponding 1,2-diamino- benzenes. Cyclization of the latter with SeCl₄ gave 6-X-4,5,7- trifluoro-2,1,3-benzoselenadiazoles.