Oxidation Of 1a Research Articles

Metal-carbon multiple bonds: novel syntheses and reactions of aminocarbyne complexes of tungsten

Syntheses and reactions of low and high valence tungsten aminocarbyne complexes are reported. The addition of LiN iPr 2 to W(CO) 6 in Et 2O affords the imidoyl complex Li[(CO) 5WC(O)N iPr 2], which is converted to the aminocarbyne complexes trans-X(CO) 4W≡CN iPr 2 (X = Cl ( 1a) or Br ( 1b) react with γ-picoline (pic), 2,2′-bipyridine (bpy) and 1.10-phenanthroline (phen) to yield the CO substitution products X(CO) 2L 2W≡CN iPr 2 ( 3a, 3b, 5a, and 6a) (L = pic ( 3); L 2 = bpy ( 5); or phen ( 6)). Analogous reactions are also observed for the dicyclohexylaminocarbyne complexes trans-X(CO) 4W≡CNCy 2 (X = Cl ( 2a) or Br ( 2b)), affording the compounds X(CO) 2L 2W≡CNCy 2 ( 4a, 7b and 8b) (L = pic ( 4); L 2 = bpy ( 7) or phen ( 8)). Complexes 1a–8b are useful starting materials for the synthesis of a variety of low and high valence tungsten aminocarbyne complexes. Thus treatment of 1a and 1b or 3a and 3b with tBuNC results in the formation of the isocyanide derivatives X(CO) 2( tBuNC) 2W≡CN iPr 2 (X = Cl ( 9a) or Br ( 9b)). Complex 9a is converted to the monocarbonyl complex Cl(CO)( tBuNC) 3 W≡ CN iPr 2 ( 10a), when it is treated with tBuNC in refluxing toluene. Complexes 3b and 4a react with NaCp and KCp ∗ ( Cp ∗ = C 5 Me 5 ) to give the half-sandwich aminocarbyne complexes Cp(CO) 2 W≡ CNR 2 ( R = iPr ( 11) or Cy ( 12)) and Cp ∗( CO) 2 W≡ CN iPr 2 ( 13) respectively. Similarly, 7b or 8b are converted to the dinuclear aminocarbyne complex NEt 4[(CO) 4Mo(μ-PPh 2) 2W(CO) 2CNCy 2] ( 14b), when they are treated with K 2[ cis-Mo(CO) 4(PPh 2) 2] and [NEt 4]Br. No carbyne-carbonyl coupling is observed in these reactions. Oxidation of 1a with PhICl 2 and 1b with Br 2 in 1,2-dimenthoxyethane (DME) affords after elimination of all CO ligands the 16-electron aminocarbyne complexes mer-X 3(DME)W≡CN iPr 2 (X = Cl ( 15a) or Br ( 15b)). In comparison, oxidation of 11–13 with PhICl 2 yields the 18-electron aminocarbyne complexes Cp(Cl) 2(CO)W ≡ CNR 2 (R = iPr ( 16) or Cy ( 17)) and Cp ∗( Cl) 2 (CO)W ≡ CN iPr 2 ( 18) respectively. Restricted rotation of the amino group about the C caryneN bond is observed for the first time in the complexes 16 and 17 orignating from the competition of the carbyne and the carbonyl ligand for metal-ligand back bonding in these compounds.

Electron-transfer induced cleavage and formation of C-H-bonds in 17? and 19? platinum complexes

The electrochemical behavior of platinum complexes [Pt(η4-diene)(η5-C5R5)]+BF4− (1+, diene = C5Me5H, R = H;2+, diene = C5Me5H, R = Me;3+, diene = C6H8, R = Me;4+, diene = C8H12, R = Me) was studied by cyclic voltammetry. Complexes1+ and2+ are shown to be capable of both oxidation and reduction. One-electron reduction of2+ gives a mixture of two neutral isomeric complexes5a,b of η3-allylic and σ,π,-olefinic type due to the cleavage of C-H bonds in the methyl groups of the pentamethylcyclopentadiene ligand of 19ē complexes2. The preparative electrochemical oxidation of2+ results in cleavage of the C-H bond at the sp3-hybridized pentamethylcyclopentadiene carbon atom in 17ē dication radical22+ to give the decamethylplatinocene dication [Pt(η5-C5Me5)2]2+(BF4)2 (72+). It is shown that one-electron reduction of72+ and one-electron oxidation of5a,b is accompanied by the formation of C-H bonds to form2+.

Oxidation-Reduction Sequence for the Synthesis of Peracylated Fluorodeoxy Pentofuranosides

Abstract Oxidation of 1a with DMSO-acetic or trifluoroacetic anhydride led to the formation of a mixture of epimeric gem-diols 2 and 3 in the ratios of ≍3:1 and ≍7:1, respectively. Reduction of this mixture with NaBH4 followed by benzoylation and chromatography afforded 4a and 5a.

Organometallic Chemistry of Diphosphazanes. 11. Reactions of fac-[Mo(CO)3(MeCN){.eta.2-Ph2PN(Pri)PPh(DMP)}] (DMP = 3,5-Dimethyl-1-Pyrazolyl) with Diphosphazanes and Diphosphinoalkanes and Oxidative Addition with Iodine

The use of fac-[Mo(CO)(3)(MeCN)(eta(2)-L(1))] (1a) {L(1) = Ph(2)PN(Pr-i)PPh(DMP)}(2) as a precursor to metalloligands and bimetallic, heterotrimetallic, and heptacoordinated complexes is reported. The reaction of 1a with diphosphazane, dppa, or a diphosphinoalkane such as dppm or dppe yields the fac-eta(1)-diphosphine substituted metalloligands, fac-[Mo(CO)(3)(eta(2)-L(1))(eta(1)-PXP)] {PXP = dppa (2), dppm (3), and dppe (4)}. These undergo isomerization to yield the corresponding mer-diphosphine complexes (5-7). Oxidation of the uncoordinated phosphorus atom of the mer-eta(1)-dppm-substituted complex eventually provides mer-[Mo(CO)(3)-(eta(2)-L(1)){eta(1)-Ph(2)PCH(2)P(O)Ph(2)}](8). The structure of the latter complex has been confirmed by single crystal X-ray diffraction {triclinic system, P ($) over bar 1; a = 11.994(3), b = 14.807(2), c = 15.855(3) Angstrom; alpha = 114.24(1), beta = 91.35(2), and gamma = 98.95(1)degrees; Z = 2, 4014 data (F-0 > 5 sigma(F-0)), R = 0.066, R(W) = 0.069}. Treatment of the dppe metalloligand 7 with [PtCl2(COD)] yields the heterotrimetallic complex cis-[PtCl2{mer-[Mo(CO)(3)(eta(2)-L(1))(eta(1)-dppe]}(2)] (9). Attempts to prepare a related trimetallic complex with the dppm-containing metalloligand were unsuccessful; only the tetracarbonyl complex cis-[Mo(CO)(4)(eta(2)-L(1))] (1b) and cis-[PtCl2(eta(2)-dppm)] were obtained. Reaction of la with dppe in the ratio 2:1 yields the mer-mer dinuclear complex [{mer-[Mo(CO)(3)(eta(2)-L(1))]}(2)(mu-dppe)] (10) bridged by dppe. Oxidation of 1a with iodine yields the Mo(II) heptacoordinated complex [MoI2(CO)(2)(eta(3)-L(1))] (11) with tridentate PPN coordination. The same Mo(II) complex 11 is also obtained by the direct oxidation of the tetracarbonyl complex cis-[Mo(CO)(4)(eta(2)-L(1))] (1b) with iodine. The structure of 11 has been confirmed by X-ray diffraction studies {monoclinic system, Cc; a = 10.471(2), b = 19.305(3), c = 17.325(3) Angstrom; beta = 95.47(2)degrees; Z = 4, 3153 data (F-0 > 5 sigma(F-0)), R = 0.049, R(W) = 0.051}. This complex exhibits an unusual capped-trigonal prismatic geometry around the metal. A similar heptacoordinated complex 12 with a chiral diphosphazane ligand {L(3) = (S,R)-P(h)2PN-(*CHMePh)*PPh(DMP)} has also been synthesized.

Syntheses of Cyclic and Acyclic Bis(perfluoroalkylthio)nitronium Salts

Abstract(F3CS)3N (1) is oxidized quantitatively by AsF5 to the first bis(perfluoroalkylthio)nitronium salt (F3CS)2N+AsF−6 (2). Addition of halide ions (F−, Cl−, Br−, l−) to the cation of 2 destroys the SNS chain. (F2CSCl)2 undergoes with ammonia a cyclization reaction to SCF2CF2SNH (3), which can be derivatized with F3CSCl or (F2CSCl)2 to SCF2CF2SNSCF3 (3a) and (SCF2CF2SNSCF2)2 (3b), respectively. Oxidation of 3a with AsF5 yields (SCF2CF2SN+AsF−6 (4) and byproducts, which suggest formation of a {3a}+• radical cation as an intermediate in this reaction. Pure 4 is accessible by reaction of 3 with AsF5 in 54% yield. The chemical and spectroscopic properties of the new species are discussed.

Synthesis and spectroscopic properties of di-2-pyridyl sulfide (dps) compounds. Crystal structure of [Ru(dps)2Cl2

Bis(di-2-pyridyl sulfide)ruthenium(II) complexes containing the ligands CI, NO2, NO, MeCN, py (pyridine), pyz (pyrazine) or 4,4′-bipy (4,4′-bipyridine) have been prepared by usual methods and a new direct procedure from robust [Ru(dps)2CI2]1a(dps = di-2-pyridyl sulfide). This is the main product of the reaction between dps and RuCl3 in refluxing dimethylformamide (dmf) while minor products are the complexes [Ru(dps)(dmf)(CO)CI2] and [Ru(dps)2(CO)CI][PF6]. The crystal structure of 1a has been determined: orthorhombic, space group Pbcn, a= 8.587(2), b= 16.421(3), c= 15.023(3)A, Z= 4 and R= 0.024. The Ru atom exhibits an almost ideal octahedral co-ordination geometry involving two CI atoms, in cis position, and the two dps ligands chelated through the respective pyridine N atoms. Each dps adopts a twisted N,N-inside conformation. The six-membered chelate rings show boat conformations with the Ru and S atoms out of the plane through the other four atoms on the same side. Oxidation of 1a by HNO3 or cerium(IV) salts, followed by precipitation with NH4PF6, gave [Ru(dps)2CI2][PF6]. The complexes have been characterized by infrared, UV/VIS, 1H and 13C NMR spectroscopies. The 1H NMR resonances of the pyz and 4,4′-bipy derivatives were assigned by employment of correlation spectra. The lowest-energy band in the visible spectrum of 1a, assigned as a dπ(Ru)→π*(dps) transition, is blue shifted with respect to that of [Ru(2,2′-bipy)2CI2]. Further blue shifts are observed on replacing in the Cl–1a by stronger π-acceptor ligands such as NO2–, MeCN and NO+.

Inhibitors of sterol synthesis. Synthesis and spectral properties of 3β-hydroxy-5α-cholestan-15-one and its 14β-epimer and their effects on 3-hydroxy-3-methylglutaryl coenzyme A reductase activity

3β-Hydroxy-5α-cholestan-15-one ( 2a) and its 14β-epimer 2b were prepared from 3β-acetoxy-5α-cholest-8(14)-ene ( 3). Hydroboration of 3 at 45–50°C gave a mixture of 5α, 14α-cholestane-3β, 15α-diol and 5α, 14β-cholestane-3β, 15β-diol, which were separated on silica gel as their 3β- tert-butyldimethylsilyl ethers 5a and 5b. Oxidation of 5a with pyridinium chlorochromate, followed by desilylation with tetrabutylammonium fluoride gave 2a. Analogous transformations of 5b gave 2b contaminated with 2a. Desilylation of 5b followed by oxidation with pyridinium chlorochromate resulted in a mixture composed mainly of 5α, 14β-cholestane-3, 15-dione and 2b. Successive chromatographic separations on silica gel and reversed phase media gave 2b of high purity. Compound 2a was also prepared by lithium-ammonia reduction of 3β-hydroxy-5α-cholest-8(14)-en-15-one (96% yield) and by selective reduction of 5α-cholestane-3, 15-dione with lithium tri- tert-butoxyaluminum hydride (90% yield). Isomers 2a and 2b were readily epimerized under acidic or basic conditions or under conditions used for gas chromatographic analysis. The purities of 2a and 2b were measured from nuclear magnetic resonance (NMR) spectra; chromatographic methods gave less reliable estimates of purity. NMR data also showed that ring C of the 14β sterols is predominantly in a chair conformation. The effects of 2a and 2b on the levels of 3-hydroxy-3-methylglutaryl coenzyme A reductase have been studied in Chinese hamster ovary cells.

Synthesis and properties of 2-(3,5-di-tert-butyl-4-hydroxyphenyl)-5-nitroindazole

N-(2-Azido-5-nitrobenzylidene)-3,5-di-tert-butyl-4-hydroxyaniline (3a) and N-(2-azido-5-nitrobenzilidene) aniline (3b), when heated in dimethylformamide yielded 2-(3,5-di-tert-butyl-4-hydroxyphenyl)-5-nitroindazole (4a) and 2-phenyl-5-nitroindazole (4b), respectively. The structure of4b was confirmed by X-ray analysis. A stable phenoxyl radical was shown to originate from the oxidation of4a with lead (IV) dioxide.

Synthetic Studies on Colchicine: Reaction of Homomorphinandienones

For the purpose of synthetic approaches toward colchicine (2) from O-methylandrocymbine (1a), reaction of homomorphinandienones (1a, b) was carried out. Oxidation of 1a, b with 35% aqueous hydrogen peroxide gave a separable diastereomeric mixture of N-oxides (5, 6). Polonovski reaction of the N-oxides (5) with acetic anhydride in CH 2 Cl 2 afforded N-demethyl-N-acetamide (7a), whereas that of 5 and 6 with acetic anhydride in the presence of triethylamine gave enamines (8a, b) together with N-demethyl-N-acetamides (7a, b). Furthermore, reaction of enamines (8a, b) with N-bromosuccinimide in dimethoxyethane-H 2 O or methanol produced α-bromo amides (9a, b)

Darstellung und eigenschaften von und reaktionen mit metallhaltigen heterocyclen: LXXXII. Cyclocotrimerisierung der P=icr;S-Gruppe mit dem sterisch anspruchsvollen t-Butylpropinoat

The P=icr;S functional group in (η 2-PCy 2 ▪S)Mn(CO) 4 ( 1) undergoes cyclocotrimerization with t-butyl propynoate to give the isomeric compounds 3a und 3b in a 1 : 1 ratio. Oxidation of 3a and 3b with (NH 4) 2[Ce(NO 3) 6] gives thiophene 4. Compounds 3a and 3b were characterized by use of MS spectrometry and IR, 31P{ 1H}, 1H, and 13C{ 1H} NMR spectroscopy.

Synthesis and pharmacological studies of some pyrone and benzodifuran derivatives

The michael adducts2a,b were obtained from the reaction of the phenylacetyl derivative1 with benzaldehyde and p-anisaldehyde respectively.2a and2b were subjected to react with cyanoethanoic acid hydrazide, malononitrile, cyanothioacetamide, cyanoacetamide and 1,1,3-tricyano-2-amino propene to yield4a-h and5a,b respectively. Hydrogen peroxide oxidation of2a,b gave the aurone derivative6a,b. The pyrone derivatives8a,b were obtained from2a,b by addition of chloroacetyl chloride followed by dehydrochlorination.

Synthesis of phosphites and phosphates of neuraminic acid and their glycosyl donor properties ? convenient synthesis of GM3

The importance and requirements for catalytic activation of sialyl donors are discussed, leading to the acid sensitive phosphite and phosphate moiety, respectively, as leaving group and nitriles as solvent. Therefore, from readily available N-acetylneuraminic acid, derivative 1 with phosphochloridites 2a-f and Huenigs' base sialyl phosphites 3a-f were prepared and isolated in high yields. Oxidation of 3a,c with tert-butyl-hydroperoxide afforded the corresponding phosphates 4a,c. As expected, phosphites 3 could be activated in acetonitrile by catalytic amounts of TMSOTf; thus, from 3a-e as donors and lactose derivatives 8A,B as acceptors the ganglioside building blocks 9A and 9B, respectively, were obtained in good yields. The best results were obtained with diethyl phosphite derivative 3a as sialyl donor, which exceeded by far the results obtained with the corresponding phosphate derivative 4a. Trisaccharide 9B was transformed into known 9A and into the fully O-acetylated GM3-trisaccharide 10.

Carbonyl O‐Oxides and Dioxiranes: The Influence of Substituents on Spectroscopic Properties

AbstractTriplet 4‐oxocyclohexadienylidenes 6, matrix‐isolated in Ar/ 2% O2 at 10 K, react with triplet O2 on annealing the matrix. Primary reaction products are quinone oxides 4, which have been characterized by IR and UV/Vis spectrometry. They are very photolabile; long‐wavelength irradiation converts them into spiro‐dioxiranes 5, which in turn yield lactones 10 upon irradiation with visible light. Experimental data have been obtained for quinone oxides 4a–g; additionally, ground‐state properties and UV/Vis absorptions of quinone oxides 4a,b and 4e–1 have been calculated by the MINDO‐3/UHF and CNDO/S methods. Since the theoretical and experimental maxima of the π → π* transitions are in good agreement, we conclude that our semiempirical calculations give an adequate picture of quinone oxides 4 which may best be described as dipolar diradicals.

Synthesis and properties of aromatic amine-bridged PcRu(II) coordination compounds

Three aromatic amine-bridged coordination compounds [ PcRuL] n { L = p-phenylenediamine (ppd) ( 1a), 2,7-diaminofluorene (daf) ( 2a), 4-aminopyridine (apy) ( 3a)} were prepared by the reaction of PcRu(II) with the corresponding ligands, ppd, daf and apy, in order to study their properties as axial ligands in oxidation reactions. The compounds 1a, 2a and 3a were characterized by elemental analyses, 13C CPMAS ( 1a, 3a), IR and UV-Vis spectroscopy and TG/DTA analyses. Oxidation (doping) of 1a, 2a and 3a with iodine in toluene gave the corresponding axial ligand-centred oxidation products as quinoid forms 1b and 2b. In contrast, compound 3a led to the Pc-macrocycle oxidation form 3b with I 5 − polyiodide chainm as confirmed by Raman spectroscopy. Oxidation of 1a with H 2O 2/HCl and (NH 4) 2S 2O 8/HCl in aqueous solution also showed the axial ligand oxidation products 1c, 1d. The oxidized products 1b, 1c, 1d and 2b show increased conductivity between 2.1 × 10 −3 and 4.0 × 10 −6S/cm in comparison to the precursor systems.

1,2-Disiladioxetanes: structure, rearrangement and reactivity

The low-temperature reaction of (E)-1,2-dimesityl-1,2-di-tert-butyldisilene (1a) with dioxygen gives (E)-1,2-dimesityl-1,2-di-tert-butyldisiladioxetane (2a), the structure of which has been established by X-ray crystallographic analysis. This result establishes that both oxidation of 1a and rearrangement of 2a to 1,3-cyclodisiloxane 4a take place with retention of configuration at silicon. Disiladioxetane 2a forms monoclinic crystals, space group C2/c. extra electron density found above and below the Si-Si bond was shown by 1 H and solid-state 29 Si NMR to be due to 4a, arising from rearrangement of 2a in the solid. X-ray crystal structures were determined for crystals that were 5.6%, 15.2%, and 20.3% rearranged

Redoxreaktivität Phosphido‐verbrückter Heterodimetallkomplexe

Redox Reactivity of Phosphido‐Bridged Heterodimetallic ComplexesThe metal‐metal bond in (3a,b,e) [LCO: RPh (a), Cy (e); LPMe3: RPh (b)] is cleaved reductively, oxidatively, and by nucleophiles by using Na[HBEt3], bromine or iodine, and PMe3, respectively. The action of PMe3 on 3a affords Me3P(OC)4Mn – PPh2 – Fe(CO)4 (5), which is photolyzed to give 3b. While the reduction of 3a can be regarded as a nucleophilic bond opening functionalizing only manganese, oxidation of 3a,b with halides results in the formation of the complexes XMn(CO)4 – PPh2 – Fe(X)(CO)3L (4a – d) [LCO: XI (a), Br (c); LPMe3: XI (b), XBr (d)], which provide two functionalized metals. To elucidate the redox behavior of 3a cyclovoltammetric investigations were carried out. They indicate a complex reaction scheme including reactions of higher order.

Oxidation of bis(tert-butylthio) selenide at low temperatures: search for a bis(alkylthio) selenoxide

Oxidation of bis(tert-buthylthio) selenide, t-BuSSeSBu-t (1a), by peracetic acid at −40°C leads to a monooxidation product (1a-O) whose 1 H (two singlets) and 13 C NMR spectra (four resonances) show that the two tert-butyl groups in 1a-O are magnetically nonequivalent. Oxidation of 1a by peracid is examinated

Nucleic acid related compounds. 63. Synthesis of 5′-deoxy-5′-methyleneadenosine and related Wittig-extended nucleosides

Treatment of the purified 5′-aldehyde (2a) (derived from 6-N-benzoyl-2′,3′-O-isopropylideneadenosine (1a)) with methylenetriphenylphosphorane and successive deprotection with ammonia and acid gave 9-(5,6-dideoxy-β-D-ribo-hex-5-enofuranosyl)adenine (5′-deoxy-5′-methyleneadenosine) (4). Oxidation of 1a or 2′,3′-O-isopropylideneadenosine (1b) and treatment of the crude 5′-aldehydes (2a or 2b) with (p-toluenesulfonylmethylene)triphenylphosphorane gave high yields of the 5′-deoxy-5′-tosylmethylene derivatives (5a or 5b). Removal of the tosyl group from 5b to give 3b was effected with tributylstannyllithium, but sulfone cleavage by the usual reductive methods failed. Reduction and deprotection of 5a or 5b gave 9-[5,6-dideoxy-6-(p-toluenesulfonyl)-β-D-ribo-hexofuranosyl]adenine (6b). Isomerization of the vinyl tosyl (5b) to a 4′,5′-unsaturated allylic tosyl derivative (7) occurred under cleavage conditions and in solutions of aqueous or organic bases. Key words: adenosine, 5′-deoxyadenosine, 5′-methylene-5′-deoxyadenosine, nucleosides.

ORGANIC PHOSPHORUS COMPOUNDS 93.1PREPARATION, PROPERTIES AND HERBICIDAL ACTIVITY OF 2-SUBSTITUTED 5-PHENOXY- AND 5-PYRIDY LOXY-PHENYLAMINOALKYLPHOSPHONIC-AND-PHOSPHINIC ACILAS WELL AS-PHOSPHINE OXIDE DERIVATIVES*

Abstract Interaction of 4-phenoxy and 4-pyridyloxy substituted 1.2-dinitrobenzenes and aminoalkylphosphonates,-phosphinates, and -phosphine oxides produces mainly 5-phenoxy- and 5-pyridyloxy substituted 2-nitrophenylaminoalkyIphosphonates. -phosphinates and -phosphine oxides (Table I to IV and Figure 1 to 5). some of which show high herbicidal and plant growth regulating activity. The herbicidal activity increases from pyridyloxy-phenylaminoalkylphosphonates to phenoxy-phenylaminoalkyl-phosphonates, -phosphinates, -phosphine oxides. Of all the compounds tested the phosphine oxide 4a was at all concentrations the most active compound.

Komplexchemischer Aufbau cyclischer 1,2‐Dithiolato‐Liganden mit dem nido‐Cluster [(CO)3FeS]2. — Molekülstruktur und partielle S‐Oxidation von Hexacarbonyl(μ2‐cis‐1,2‐cyclohexandithiolato‐S,S)dieisen

Complex‐Chemical Synthesis of Cyclic 1.2‐Dithiolato Ligands with the nido Cluster [(CO)3,FeS]2. — Molecular Structure and Partial S‐Oxidation of Hexacarbonyl(μ2,‐cis‐1,2‐cyclohexanedithiolato‐S,S)diironThe cyclic alkenes, dienes, and trienes C6H10, C8C14, C5H6, C8C12 and C7H8 are inserted into the S‐S bond of the nido cluster [(CO)3FeS]2 (1) by photochemically induced [2+2] cycloaddition reactions to give the complexes 2–6; thus, saturated and unsaturated cyclic 1,2‐dithiolato ligands can be selectively built onto the complex in a μ2‐bridging fashion. According to an X‐ray structure analysis, the μ2‐1,2‐cyclohexanedithiolato‐S,S complex 2a with the pseudotetrahedral skeleton [(CO)3FeS]2 crystallizes in the monoclinic space group P21/c; the S2 moiety is bridged by cyclohexane with 1,2‐cis configuration. As an example, the partial S oxidation of 2a was carried out, leading to 2b by selective transformation of one thiolato into a sulfenato function.