Expansion of the pentafluorobenzene ring of perfluoro-1,2-diethyl-1-phenylbenzocyclobutene under the action of SbF5

Perfluoro-1,2-diethyl-1-phenylbenzocyclobutene under the action of SbF₅ gives, after treatment of the reaction mixture with water, perfluoro-4-[1-(6-propyl-phenyl)-propylidene]cyclohexa-2,5-dienone along with the products of unusual pentafluorobenzene ring expansion - perfluorinated 4b,10-diethylbenzo[a]azulen-7(4bH)-one and 10-ethylbenzo[a]azulen-6(10H)-one.     

Reaction of perfluoro-1-ethylindan with SiO2/SbF5 and skeletal transformations of perfluoro-3-ethylindan-1-one under the action of SbF5 and SiO2/SbF5

Perfluoro-1-ethylindan heated with excess of SiO₂ in an SbF₅ medium at 75 °C and then treated with water, gives 4-carboxy-perfluoro-3-methylisochromen-1-one. Perfluoro-3-ethylindan-1-one is converted, under the action of SbF₅ at 70 °C, to perfluoro-2-(but-2-en-2-yl)benzoic acid as a mixture of E- and Z-isomers. When the reaction temperature is raised to 125 °C, a solution of salts of perfluoro-3,4-dimethyl-1H-isochromen-1-yl and perfluoro-4-ethyl-1H-isochromen-1-yl cations is obtained. Increase in the reaction time lowers the content of a salt of the latter cation in the solution. Hydrolysis of the solution of the salts gives perfluoro-3,4-dimethylisochromen-1-one and perfluoro-4-ethylisochromen-1-one.     

Oxygen replacement by fluorine in carbonyl derivatives of perfluoroaromatic compounds and isomerization of perfluoroindan-1,3-dione to perfluoro-3-methylenephthalide under the action of HF/SbF5

When acted upon by HF/SbF₅ at 95 °C, carbonyl groups of perfluorinated acetophenone (10), 3,4-dihydronaphthalen-1(2H)-one (8), 2,3-dihydronaphthalene-1,4-dione (9), benzocyclobutenone (6), benzocyclobutenedione (7) and indan-1-one (1) are converted into difluoromethylene groups to give the corresponding perfluoroaromatic products. Perfluoroindan-2-one (5), under the same conditions, is transformed to bis(perfluoroindan-2-yl) ether (21). On heating with HF/SbF₅, perfluoroindan-1,3-dione (2) isomerizes into perfluoro-3-methylenephthalide (4) at 95 °C, and gives 4,5,6,7-tetrafluoro-3-trifluoromethyl-phthalide (14) at 130 °C. Compound 4 in the absence of a solvent dimerizes giving perfluorodispiro[phthalide-3,1′-cyclobutane-2′,3″-phthalide] (18), and when heated with SbF₅ at 130 °C, it is converted into perfluoro-3-methylphthalide (3). When acted upon by HF/SbF₅ at 95 °C, perfluorinated benzoic acid (12) and phthalic anhydride (13) give the corresponding products with trifluoromethyl groups.     

Formation and skeletal transformations of perfluoroindan-1-one and perfluoroindan-1,3-dione in the reaction of perfluoroindan with SiO2/SbF5

Perfluoroindan-1-one (2) is obtained in the reaction of perfluoroindan (1) with SiO₂/SbF₅ at 70 °C. Compound 1 heated with SiO₂/SbF₅ at 130 °C and then treated with water, gives 3-hydroxy-perfluoro-3-methylphthalide (4). Ketone 2 is converted, under the action of SbF₅ at 130 °C, to perfluoro-2-ethylbenzoic acid (9) and disproportionates to compound 1 and perfluoroindan-1,3-dione (3); the latter is transformed to phthalide 4 under the reaction conditions.     

The metathesis reactions of [SNS][SbF6] and [SN][AsF6] with Li[Al(OC(CF3)3)4] in liquid SO2

The small di- and triatomic molecules [SN]⁺ and [SNS]⁺ have shown versatile chemistries and [SNS]⁺ is an important starting reagent for many sulfur-nitrogen radicals. However, their chemistry is limited to the more polar solvents (e.g. SO₂). In this work an attempt is made to increase their solubility in less polar solvents by exchange of the usual [MF₆]⁻ (M = As, Sb) anions by the large and weakly coordinating [Al(OC(CF₃)₃)₄]⁻. As expected the metathesis reactions of [SN][AsF₆] and [SNS][SbF₆] with Li[Al(OC(CF₃)₃)₄] in liquid sulfur dioxide resulted in the formation of the insoluble Li[SbF₆], which is the driving force for these metathesis reactions. The characterization of the compounds by IR and multinuclear NMR revealed that [SNS]⁺ formed a [Al(OC(CF₃)₃)₄]⁻ salt in a clean reaction. A preliminary crystal structure of [SNS][Al(OC(CF₃)₃)₄] is presented. The solubility of [SNS][Al(OC(CF₃)₃)₄] in CH₂Cl₂ is significantly increased with respect to the corresponding [MF₆]⁻ salts, and potentially opens up new areas of [SNS]⁺ chemistry. The reaction of the more reactive [SN]⁺ with Li[Al(OC(CF₃)₃)₄] was less clear. Multinuclear NMR and IR spectra were consistent with the formation of [SN][Al(OC(CF₃)₃)₄], which also showed significant decomposition.     

Preparation and conformational study of CF3-containing enkephalin-derived oligopeptide

Incorporation of (2S,3S)-4,4,4-trifluorothreonine (F₃-Thr) instead of Thr in the enkephalin-derived hexapeptide led to the apparent conformational alteration due to the strong electron-withdrawing effect of the trifluoromethyl group by comparison with the original compound on the basis of their various NMR measurements.     

Skeletal transformations of perfluorinated 2,2-diethyl- and 2-ethyl-2-phenyl-benzocyclobutenones under the action of antimony pentafluoride

Perfluoro-2-ethyl-2-phenylbenzocyclobutenone heated with SbF₅ at 70 °C and then treated with water, forms perfluoro-3-ethyl-3-phenylphthalide. In contrast to this, heating of perfluoro-2,2-diethylbenzo-cyclobutenone with SbF₅ at 70 °C gives, after treatment of the reaction mixture with water, perfluoro-2-(pent-2-en-3-yl)benzoic acid. When the reaction temperature is raised to 125 °C, a solution of a salt of perfluoro-4-ethyl-3-methylisochromenyl cation is obtained. Hydrolysis of the solution of the salt gives perfluoro-4-ethyl-3-methylisochromen-1-one.     

Gas phase structure and conformational properties of trifluoroacetic anhydride, CF3C(O)OC(O)CF3

The geometric structure of trifluoroacetic anhydride, CF₃C(O)OC(O)CF₃, has been studied by gas electron diffraction (GED) and quantum chemical calculations (MP2 and B3LYP with 6-31G^* basis sets). The GED analysis results in a single conformer with synperiplanar orientation of the two CO bonds. This analysis, however, cannot discriminate between a planar equilibrium structure (C_2v symmetry) with large amplitude torsional motions around the OC bonds and a nonplanar equilibrium structure (C₂ symmetry) with a low barrier at the planar arrangement. An effective dihedral angle φ(COCO=18(4)° is obtained. Both quantum chemical methods predict a nonplanar equilibrium structure of C₂ symmetry and φ(COCO)=16.5° and 13.9°, respectively.     

Alkynethiolate ligands in the syntheses of iron carbonyl derivatives. Crystal structure of [(η-C5H5)Fe(CO)2(SCCSiMe3)]

The complexes [(η⁵-C₅H₅)Fe(CO)₂(SCCR)] (R=^tBu, SiMe₃) have been obtained by reaction of [(η⁵-C₅H₅)Fe(CO)₂I] and the corresponding LiSCCR. These are the first examples of mononuclear iron compounds containing alkynethiolate ligands. The crystal structure of [(η⁵-C₅H₅)Fe(CO)₂(SCCSiMe₃)] has been determined by X-ray diffraction. The role of [(η⁵-C₅H₅)Fe(CO)₂(SCCSiMe₃)] as a metalloligand in its reactions with metal carbonyls has been explored.     

Imino Diels-Alder reactions: an efficient one-pot synthesis of pyrano and furanoquinoline derivatives catalyzed by SbCl3

Antimony trichloride (SbCl₃) was found to be an efficient catalyst for the inverse electron demand imino Diels-Alder reactions of in situ generated N-benzylidenes with 3,4-dihydro-2H-pyran and 2,3-dihydrofuran to afford pyrano and furano[3,2-c]quinolines in excellent yields.     

Reactions of fluorinated acid anhydrides, (CF3CO)2O, (CF3SO2)2O and (FSO2)2O, with organometallic substrates of group 15 (As, Sb and Bi)

(C₆H₅)₃MX₂ (M = As, Sb; X = OCOCF₃ and M = Sb, Bi; X = SO₃F, SO₃CF₃) compounds prepared by the interaction of triphenylmetal(V) substrates with (CF₃CO)₂O, (CF₃SO₂)₂O and (FSO₂)₂O have been characterized by molecular weight determination, elemental and spectroscopic (IR, ¹H and ¹⁹F NMR, mass) analyses.     

Novel ammonium hexafluoroarsenate salts from reaction of (CF3)2NH,CF3N(OCF3)H,CF3N[OCF(CF3)2]H,CF3NHF and SF5NHF with the strong acid HF/ASF5.

Reactions of the fluorinated amines (CF₃)₂NH, CF₃N(OCF₃)H, CF₃N[OCF(CF₃)₂]H, CF₃NHF and SF₅NHF with the strong acid HF/AsF₅ form the corresponding ammonium salts R_f¹R_f²NH₂⁺AsF₆^? and R_fNFH₂⁺ AsF₆^? in high yield. [R_f¹=CF₃, R_f²=CF₃, CF₃O, (CF₃)₂CFO; R_f=CF₃, SF₅] The colorless crystalline solids are stable for prolonged periods at 22°C in sealed FEP containers. They have dissociation pressures at 22°C ranging from ～5 torr (R_fNFH₂⁺ AsF₆^?) to ～50 torr [CF₃N(OCF₃)H₂⁺AsF₆^?]. ¹⁹F NMR and Raman spectroscopy were used to identify the compounds.     

Synthesis of functionalized 5-(3-R-1-adamantyl)uracils and related compounds

Efficient synthetic approaches to functionalized 5-(3-R-1-adamantyl)uracils and related compounds (R=OH, COOH, NH₂, etc.) are described. The selective hydroxylation of the adamantane tertiary C-H bonds in 5-(1-adamantyl)uracils with H₂SO₄ in trifluoroacetic anhydride is used as the key step. Subsequent electrophilic reactions of 5-(3-hydroxy-1-adamantyl)uracils with N- and C-nucleophiles in CF₃COOH, H₂SO₄ or H₂SO₄/AcOH media yielded derivatives with amide, amino, aryl, carboxy and thiourea groups in the adamantane core. The preliminary evaluation of the antiviral activity revealed that some of the synthesized species display moderate antiviral activity against HSV-1 (SI∼20) in Vero cells.     

New heterodimetallic cyclopentadienyl carbonyl complexes: crystal structure of (C5Me4Et)(μ-CO)3Ru(C5Me5)

A series of heterodimetallic complexes of general formula (C₅R₅)M(μ-CO)₃RuC₅Me₅ (M = Cr, Mo, W; R = Me, Et) has been prepared in good yields by the reaction of [C₅R₅M(CO)₃]⁻ with [C₅Me₅Ru(CH₃CN)₃]⁺. (C₅Me₄Et)W(μ-CO)₃Ru(C₅Me₅) was characterized by a crystal structure determination. The W---Ru bond length of 2.41 Å is consistent with the formulation of a metal-metal triple bond, while the unsymmetrical bonding mode of the three bridging carbonyl groups reflects the inherent non-equivalence of the two different C₅R₅M-units. Using [CpRu(CH₃CN)₃]⁺ or [CpRu(CO)₂(CH₃CN)]⁺ as the cationic precursor leads to the formation of dimetallic species (C₅R₅)M(CO)₅RuC₅H₅ with both bridging and terminal carbonyl groups.     

On the behaviour of Ru(I) and Ru(II) carbonyl acetates in the presence of H2 and/or acetic acid and their role in the catalytic hydrogenation of acetic acid

The reactivity of phosphine substituted ruthenium carbonyl carboxylates Ru(CO)₂(MeCOO)₂(PBu₃)₂, Ru₂(CO)₄(μ-MeCOO)₂(PBu₃)₂, Ru₄(CO)₈(μ-MeCOO)₄(PBu₃)₂ with H₂ and/or acetic acid was investigated by IR and NMR spectroscopy to clarify their role in the catalytic hydrogenation of acetic acid. Evidences were collected to suggest hydride ruthenium complexes as the catalytically active species. Equilibria among ruthenium hydrides and carboxylato complexes take place in the presence of hydrogen and acetic acid, that is in the conditions of the catalytic reaction. Nevertheless the presence of acetic acid reduces the rate of the formation of hydrides. Working at a very high temperature (180°C) polynuclear phosphido hydrides such as [Ru₆(μ-H)₆(CO)₁₀(μ-PHBu)(μ-PBu₂)₂(PBu₃)₂(μ₆-P)] were formed. These phosphido clusters are suggested as the resting state of the catalytic system.Furthermore the bi- or tetranuclear Ru(I) carboxylato complexes react with acetic acid giving a mononuclear ruthenium complex Ru(CO)₂(MeCOO)(μ-MeCOO)(PBu₃), containing a monodentate and a chelato acetato ligands. This complex was spectroscopically characterised. Its identity and structure were confirmed by its reactivity with stoichiometric amount of PPh₃ to give Ru(CO)₂(MeCOO)₂(PBu₃)(PPh₃), a new mononuclear ruthenium carbonyl carboxylate containing two different phosphines, that was fully characterised.     

Preparation and characterization of [Re(bpy)(CO) 3L][SbF6] (L = phosphine, phosphite)

A series of rhenium complexes [fac-Re(bpy)(CO)₃L][SbF₆] (bpy = 2,2′-bipyridine, L = P(ⁿBu)₃, PEt₃, PPh₃, P(OMe)Ph₂, P(OⁱPr)₃, P(OEt)₃, P(OMe)₃, P(OPh)₃) has been prepared and characterized by the IR, UV-vis, ¹H NMR, ³¹P NMR, X-ray photoelectron spectroscopy and electrochemical techniques. Variations in the electronic properties, i.e. CO stretching, metal-to-ligand charge transfer transition, and ³¹P NMR chemical shifts were interpreted on the basis of the electron-acceptor strength of L. However, the redox potential corresponding to [Re(bpy)(CO)₃L]⁺/[Re(bpy⁻)(CO)₃L]showed ‘V-character type’ changes after the increase in the electron-acceptor strength of L. Variation of the P(2p) binding energy of the phosphorus atom indicated that the electronic structure of the coordinated phosphorus atom was strongly influenced by the electronic properties of the directly attached substituents.     

Synthesis and crystal structure of the novel trimanganese tetrathiolate incomplete cubane: [Mo(η-C5H5)2(H)CO][Mn3(CO)9(μ-SC6H5)4]

An unexpected trimanganese(I) tetrathiolate-bridged complex, [Mn₃(CO)₉(μ-SC₆H₅)₄]⁻, with an incomplete cubane structure, was obtained by thermal reaction of [Mn₂(CO)₁₀] with [Mo(η⁵-C₅H₅)₂(SC₆H₅)₂]. The structure, established by single-crystal X-ray diffraction studies, shows the cation, [Mo(η⁵-C₅H₅)₂(H)CO]⁺, directed towards the vacant site of the cubane structure. Possible routes by which the anion and the cation could be formed are discussed.     

Five-coordinate pentafluorobenzothiolate osmium(IV) complexes [Os(SC6F5)4(P(C6H4X-4)3)] (X = OCH3, CH3, F, Cl or CF3): Solid and solution structural characterization

The reactions of OsO₄ with excess of HSC₆F₅ and P(C₆H₄X-4)₃ in ethanol afford the five-coordinate compounds [Os(SC₆F₅)₄(P(C₆H₄X-4)₃)] where X = OCH₃ 1a and 1b, CH₃ 2a and 2b, F 3a and 3b, Cl 4a and 4b or CF₃ 5a and 5b. Single crystal X-ray diffraction studies of 1 to 5 exhibit a common pattern with an osmium center in a trigonal-bipyramidal coordination arrangement. The axial positions are occupied by mutually trans thiolate and phosphane ligands, while the remaining three equatorial positions are occupied by three thiolate ligands. The three pentafluorophenyl rings of the equatorial ligands are directed upwards, away from the axial phosphane ligand in the arrangement “3-up” (isomers a). On the other hand, ³¹P{¹H} and ¹⁹F NMR studies at room temperature reveal the presence of two isomers in solution: The “3-up” isomer (a) with the three C₆F₅-rings of the equatorial ligands directed towards the axial thiolate ligand, and the “2-up, 1-down” isomer (b) with two C₆F₅-rings of the equatorial ligands directed towards the axial thiolate and the C₆F₅-ring of the third equatorial ligand directed towards the axial phosphane. Bidimensional ¹⁹F–¹⁹F NMR studies encompass the two sub-spectra for the isomers a (“3-up”) and b (“2-up, 1-down”). Variable temperature ¹⁹F NMR experiments showed that these isomers are fluxional. Thus, the ¹⁹F NMR sub-spectra for the “2-up, 1-down” isomers (b) at room temperature indicate that the two S-C₆F₅ ligands in the 2-up equatorial positions have restricted rotation about their C–S bonds, but this rotation becomes free as the temperature increases. Room temperature ¹⁹F NMR spectra of 3 and 5 also indicate restricted rotation around the Os–P bonds in the “2-up, 1-down” isomers (b). In addition, as the temperature increases, the ¹⁹F NMR spectra tend to be consistent with an increased rate of the isomeric exchange. Variable temperature ³¹P{¹H} NMR studies also confirm that, as the temperature is increased, the a and b isomeric exchange becomes fast on the NMR time scale.     

Ru3(CO)12-catalyzed intramolecular allylic transfer reaction of tethered carbonyl group and allylic acetate moiety

A ruthenium catalyzed intramolecular allylic transfer reaction of allylic acetates containing aldehydes or ketones to form cis-homoallylic cyclopentanols and cyclohexanols as a major component is described. The use of Ru₃(CO)₁₂ (1 mol %) to promote reaction results in a convenient procedure for intramolecular allylation of carbonyl functionalities.     

Synthesis and characterization of Na5[Co(CO)3(P{(CH2)nC6H4-P-SO3}3)2], n = 1, 2, 3, and 6. Novel zwitterion

The electron donating water soluble phosphines, P{(CH₂)nC₆H₄-p-SO₃Na}₃,n = 1, 2, 3 and 6, react rapidly with Co₂(CO)₈ under two phase reaction conditions to yield the disproportionation products, [Co(CO)₃(P{(CH₂)nC₆H₄-p-SO₃Na₃}₂] [Co(CO)₄]. Selective precipitation yields the formally zwitterionic complex anions as the sodium salt, [Co(CO)₃(P{(CH₂)nC₆H₄-p-SO₃} ₃)₂]⁵⁻. The anions can be used as precursors to water soluble cobalt hydroformylation catalysts under two phase and supported aqueous phase conditions. The tendency to form alcohol products is low with these complexes. The behavior of the catalysts is consistent with an active species that remains water soluble during the reaction and is not leached into the nonaqueous phase.