Condensed metallaborane clusters: synthesis and structure of Fe2(CO)6(eta5-C5Me5RuCO)(eta5-C5Me5Ru)B6H10

Mild pyrolysis of (eta5-C5Me5Ru)2B6H12 with Fe2(CO)9 yields the 12 skeletal electron pair (sep) Fe2(CO)6(eta5-C5Me5RuCO)(eta5-C5Me5Ru)B6H10 cluster; the title compound represents a novel class of hybrid multiple cluster in which a Fe2B2 tetrahedron has been fused to a ruthenaborane substrate.     

Stabilisation of [WF5]+ and WF5 by Pyridine: Facile Access to [WF5(NC5H5)3]+ and WF5(NC5H5)2

The enhanced reactivity of [WF₅]⁺ over WF₆ has been exploited to access a neutral derivative of elusive WF₅. The reaction of WF₆(NC₅H₅)₂ with [(CH₃)₃Si(NC₅H₅)][O₃SCF₃] in CH₂Cl₂ results in quantitative formation of trigonal-dodecahedral [WF₅(NC₅H₅)₃]⁺, which has been characterised as its [O₃SCF₃]⁻ salt by Raman spectroscopy in the solid state and variable-temperature NMR spectroscopy in solution. The salt is susceptible to slow decomposition in solution at ambient temperature via dissociation of a pyridyl ligand, and the resultant [WF₅(NC₅H₅)₂]⁺ is reduced to WF₅(NC₅H₅)₂ in the presence of excess C₅H₅N, as determined by ¹⁹F NMR spectroscopy. Pentagonal-bipyramidal WF₅(NC₅H₅)₂ was isolated and characterised by X-ray crystallography and Raman spectroscopy in the solid state, representing the first unambiguously characterised WF₅ adduct, as well as the first heptacoordinate adduct of a transition-metal pentafluoride. DFT-B3LYP methods have been used to investigate the reduction of [WF₅(NC₅H₅)₂]⁺ to WF₅(NC₅H₅)₂, supporting a two-electron reduction of W^VI to W^IV by nucleophilic attack and diprotonation of a pyridyl ligand in the presence of free C₅H₅N, followed by comproportionation to W^V.     

Oxetane from A-nor-steroides: 2-alpha, 5-oxido-A-nor-5-alpha-cholestane, 2-beta, 5-oxido-A-nor-5-beta-cholestane and 2-alpha-ethyl-2-beta,2'-oxido-A-nor-5-alpha-cholestane

Treatment of 2β-tosyloxy-A-nor-5α-cholestane-5-ol ( 2 ) with t-butoxide in t-butanol gave 2α, 5-epoxy-A-nor-5α-cholestane ( 3 ) in quantitative yield. When A-nor-5β-cholestane-2α, 5-diol ( 4 ) was treated with tosyl chloride in pyridine 2β-chloro-A-nor-5β-cholestane-5-ol ( 7 ) and 2α-tosyloxy-A-nor-5β-cholestane-5-ol ( 8 ) were obtained. Whereas the chloride 7 was resistant to t-butoxide the tosylate 8 was transformed into an 1 : 1 mixture of 2α, 5-epoxy-5β-cholestane ( 10 ) and 2ξ-t-butoxy-A-nor-5β-cholestane-5-ol ( 11 ). In 2α-tosyloxy-A-nor-5α-cholestane-5-ol ( 12 ) substitution occurred as the only reaction. Both oxetanes 3 and 10 isomerize after heating above 50° and in polar or protic solvents to form A-nor-Δ³⁽⁵⁾-cholestene-2α-ol ( 6 ) and -2β-ol ( 14 ) respectively. Also, 2, 5-diols are encountered. 2α-Ethyl-2β, 2′-epoxy-A-nor-5α-cholestane ( 23 ) was synthesized starting from A-nor-5α-cholestane-2-one ( 17 ). The intermediates were the ester 16 , the diol 18 , the hydroxy-tosylate 19 and the chlorhydrin 20 . The spirocyclic oxetane 23 was reduced by LiAlH₄ in dioxane (not in ether). By chromatography on silica gel 23 was isomerized to the homoallylic alcohol 21 and transformed into 2-methylene-A-nor-5α-cholestane ( 24 ) by fragmentation. The IR. and NMR. spectra of the new oxetanes were compared with those of a series of known oxetanes.     

Synthesis of (C5Me5)2(C5Me4H)UMe, (C5Me5)2(C5H5)UMe, and (C5Me5)2UMe[CH(SiMe3)2] from cationic metallocenes for the evaluation of sterically induced reduction

To probe the correlation of unusual (C5Me5)(1-) reactivity with steric crowding in complexes such as (C5Me5)3UMe and (C5Me5)3UCl, slightly less crowded (C5Me5)2(C5Me4H)UX analogues (X = Me, Cl) were synthesized and their reactivity was evaluated. The utility of the cationic precursors [(C5Me5)2UMe](1+), 1, and [(C5Me5)2UCl](1+), 2, in the synthesis of (C5Me5)2(C5Me4H)UMe, 3, and (C5Me5)2(C5Me4H)UCl, 4, was also explored. Since the use of precursor [(C5Me5)2UMe][MeBPh3], 1a, is complicated by the equilibrium between 1a and (C5Me5)2UMe2/BPh3, the reactivity of [(C5Me5)2UMe(OTf)]2, 1b, (OTf = O3SCF3) prepared from (C5Me5)2UMe2 and AgOTf, was also studied. Both 1a and 1b react with KC5Me4H to form 3. Complex 4 readily forms by addition of KC5Me4H to [(C5Me5)2UCl][MeBPh3], generated in situ from (C5Me5)2UMeCl and BPh3. Complex 1b was preferred to 1a for the synthesis of (C5Me5)2(C5H5)UMe, 5, and (C5Me5)2UMe[CH(SiMe3)2], 6, from KC5H5 and LiCH(SiMe3)2, respectively. Complex 6 is the first example of a mixed alkyl uranium metallocene complex. Sterically induced reduction (SIR) reactivity was not observed with 3-6 although the methyl displacements from the (C5Me5)(1-) ring plane for 3 are the closest observed to date to those of SIR-active complexes. The (1)H NMR spectra of 3 and 4 are unusual in that all of the (C5Me4H)(1-) methyl groups are inequivalent. This structural rigidity is consistent with density-functional theory calculations.     

Synthesis of 2, 2, 5, 5-tetramethyltetrahydrothiophene

Under the conditions of the Grignard reaction, 2, 5-dimethyl-2, 5-hexanediol has been obtained from diethyl succinate. Under the action of sulfuric acid, the latter has been cyclized to 2, 2, 5, 5-tetramethyl-tetrahydrofuran which, in its turn, by treatment with phosphorus pentasulfide, has given 2, 2, 5, 5-tetramethyltetrahydrothiophene. Its reaction with methyl iodide has given 2, 2, 5, 5-tetramethyltetrahydrothiophene methiodide.     

Concise synthesis of 5-methyl-, 5-formyl,and 5-carboxy analogues of 2′-deoxycytidine-5′-triphosphate

We describe a concise and efficient synthesis of 5-methyl-, 5-formyl-, and 5-carboxy-analogues of 2′-deoxycytidine-5′-triphosphate which are well known for their various biological applications. A protection-free one-pot synthesis was used to convert 5-methyl-2′-deoxycytidine into 5-methyl-2′-deoxycytidine-5′-triphosphate in high yield. 5-Formyl-2′-deoxycytidine-5′-triphosphate was obtained upon photosensitized oxidation (UV-A irradiation, λ ∼365 nm) of an aerated aqueous solution of 5-methyl-2′-deoxycytidine-5′-triphosphate with the use of menadione as the photosensitizer. 5-Formyl-2′-deoxycytidine-5′-triphosphate was converted into 5-carboxy-2′-deoxycytidine-5′-triphosphate by using biphasic TEMPO/BAIB oxidation method in high yield.     

Synthesis of (5R)- and (5S)-5-Methyl-5, 6-dihydrouridine Derivatives

The hydrogenation of 2′, 3′-O-isopropylidene-5-methyluridine (1) in water over 5% Rh/Al₂O₃ gave (5 R)- and (5 S)-5-methyl-5, 6-dihydrouridine (2) , separated as 5′-O-(p-tolylsulfonyl)- (3) and 5′-O-benzoyl- (5) derivatives by preparative TLC. on silica gel and ether/hexane developments. The diastereoisomeric differentiation at the C(5) chiral centre depends upon the reaction media and the nature of the protecting group attached to the ribosyl moiety. The synthesis of iodo derivatives (5 R)- and (5 S)- 4 is also described. The diastereoisomers 4 were converted into (5 R)- and (5 S)-2′, 3′,-O-isopropylidene-5-methyl-2, 5′-anhydro-5, 6-dihydrouridine (7) .     

Les Phases Na5NbO5 et Na5TaO5 Structure Cristalline de Na5NbO5

Na₅Nb0₅ and Na₅Ta0₅ Phases. Crystal Structure of Na₅NbO₅ New ternary oxides of formulas Na₅NbO₅ and Na₅TaO₅ have been prepared. They crystallize in the monoclinic system (space group C2/c). The crystal structure of Na₅NbO₅ has been determined. It derives from a NaCl-type structure by ordering of the cations and of the oxygen vacancies in the anionic sublattice, the corresponding formula being Na_5/6Nb_1/6O_5/6□_1/6. Sodium and niobium have a distorted square-pyramidal surrounding.     

2-Sulfanilamido-5-methylthio-pyrimidin und 2-Sulfanilamido-5-methylsulfonyl-pyrimidin

Zusammenfassung 2-Amino-4-hydroxy-5-methylthio-pyrimidin, gewonnen aus Formylmethylthioesigsäuremethylester und Guanidin, wird über die 4-Chlorverbindung in das 2-Amino-5-methylthio-pyrimidin umgewandelt. Für diese Reaktion bewährt sich, als neue Methode in dieser Reihe, besonders die Alkalibehandlung des aus der Chlorverbindung erhaltenen Triphenylphosphoniumsalzes. Aus dem 2-Amino-5-methylthio-pyrimidin wird das 2-Sulfanilamido-5-methylthio-pyrimidin und dessen Oxydationsprodukt, das 2-Sulfanilamido-5-methylsulfonyl-pyrimidin, gewonnen.

---

2-Sulfanilamido-5-methylthiopyrimidine and 2-sulfanilamido-5-methylsulfonylpyrimidine (New sulfonamides, XVII)

2-Amino-4-hydroxy-5-methylthiopyrimidine, obtained from guanidine and methyl formylmethylthioacetate, was first converted to the 4-chloro derivative and then to 2-amino-5-methylthiopyrimidine. The latter reaction step in this series of compounds was advantageously carried out by alkali treatment of the triphenylphosphonium salt prepared from the 4-chloro derivative. In subsequent steps, 2-sulfanilamido-5-methylthiopyrimidine and its oxidation product, 2-sulfanilamido-5-methylsulfonylpyrimidine, were prepared.

---

---

16. Mitt.:H. Egg, Mh. Chem.100, 34 (1969).     

Synthesis and Characterization of the Chiral Skeleton Cluster [NiRuMo(CO)_5(μ_3-S)(η~5-C_5H_5)(η~5-C_5H_4COCH_3)]

1 INTRODUCTION The chemistry of transition metal cluster has enjoyed an exceptional growth since the mid 1970s[1, 2], especially in recent years the structural and bonding aspects of mixed-metal tetrahedral skeleton clusters have been extensively studied[3]. One important reason is that such chiral cluster can induce an asymmetric catalysis potentially. In our research group, considerable efforts have been directed to the synthesis of chiral tetrahedral clusters containing four different…     

5′-substituted-5′-deoxy nucleosides

The methyl esters of the uronic acids derived from uridine, 5-fluorodeoxyuridine, 6-aza-2′-deoxyuridine and 2′,3′-o-isopropylideneadenosine were converted to the amides with aqueous d0·88 ammonia. After protection of the sugar hydroxyls each 5′-carboxamide was dehydrated with phosphoryl chloride at ?5° to yield, after deprotection, the respective novel 5′-nitrile nucleosides. Treatment of the protected 5′-nitrile nucleosides with ammonium azide in DMF gave, after deprotection, the novel 5′-C-tetrazole nucleosides.     

Synthesis of 5-acetoxymethyl- and 5-hydroxymethyl-2-vinyl-furan

5-Acetoxymethyl- and 5-hydroxymethyl-2-vinylfuran were synthesized by two routes. The first route starts from 2-methylfuran and the second from furfuryl acetate. The latter route, involving successive Vilsmeier-Haack and Wittig reactions, is suitable for producing 5-acetoxymethyl-2-vinylfuran and 5-hydroxymethyl-2 vinylfuran in 68% and 60%yields, respectively.     

Zinc-zinc bonded zincocene structures. Synthesis and characterization of Zn2(eta5-C5Me5)2 and Zn2(eta5-C5Me4Et)2

While, in general, decamethylzincocene, Zn(C5Me5)2, and other zincocenes, Zn(C5Me4R)2 (R = H, But, SiMe3), react with dialkyl and diaryl derivatives, ZnR'2, to give the half-sandwich compounds (eta5-C5Me4R)ZnR', under certain conditions the reactions of Zn(C5Me5)2 with ZnEt2 or ZnPh2 produce unexpectedly the dizincocene Zn2(eta5-C5Me5)2 (1) in low yields, most likely as a result of the coupling of two (eta5-C5Me5)Zn* radicals. An improved, large scale (ca. 2 g) synthesis of 1 has been achieved by reduction of equimolar mixtures of Zn(C5Me5)2 and ZnCl2 with KH in tetrahydrofuran. The analogous reduction of Zn(C5Me4R)2 (R = H, SiMe3, But) yields only decomposition products, but the isotopically labeled dimetallocene 68Zn2(eta5-C5Me5)2 and the related compound Zn2(eta5-C5Me4Et)2 (2) have been obtained by this procedure. Compound 2 has lower thermal stability than 1, but it has been unequivocally characterized by low-temperature X-ray diffraction studies. As for 1 a combination of structural characterization techniques has provided unambiguous evidence for its formulation as the Zn-Zn bonded dimer Zn2(eta5-C5Me4Et)2, with a short Zn-Zn bond of 2.295(3) A indicative of a strong Zn-Zn bonding interaction. The electronic structure and the bonding properties of 1 and those of related dizincocenes Zn2(eta5-Cp')2 have been studied by DFT methods (B3LYP level), with computed bond distances and angles for dizincocene 1 very similar to the experimental values. The Zn-Zn bond is strong (ca. 62 kcal.mol-1 for 1) and resides in the HOMO-4, that has a contribution of Zn orbitals close to 60%, consisting mostly of the Zn 4s orbitals (more than 96%).     

Electron paramagnetic resonance and spectroscopic characteristics of electrogenerated mixed-valent systems [(eta 5-C5Me5)M(mu-L)M(eta 5-C5Me5)]+ (M = Rh, Ir; L = 2,5-diiminopyrazines) in relation to the radicals [(eta 5-C5Me5)ClM(mu-L)MCl(eta 5-C5Me5)]+ and [(eta 5-C5Me5)M(mu-L)MCl(eta 5-C5Me5)]2+

Electrochemical reduction of the dinuclear [(eta 5-C5Me5)ClM(mu-L)MCl(eta 5-C5Me5)]2+ ions (M = Rh, Ir; L = 2,5-bis(1-phenyliminoethyl)pyrazine (bpip) and 2,5-bis[1-(2,6-dimethylphenyl)iminoethyl]pyrazine (bxip)) proceeds via the paramagnetic intermediates [(eta 5-C5Me5)ClM(mu-L)MCl(eta 5-C5Me5)]+ (L = bpip) or [(eta 5-C5Me5)M(mu-L)MCl(eta 5-C5Me5)]2+ (L = bxip) and [(eta 5-C5Me5)M(mu-L)M(eta 5-C5Me5)]+. Whereas the first is clearly a radical species with a small g anisotropy, the chloride-free cations are distinguished by structured intervalence charge transfer (IVCT) bands in the near-infrared region and by rhombic electron paramagnetic resonance features between g = 1.9 and g = 2.3, which suggests considerable metal participation at the singly occupied MO. Alternatives for the d configuration assignment and for the role of the bisbidentate-conjugated bridging ligands will be discussed. The main difference between bpip and bxip systems is the destabilization of the chloride-containing forms through the bxip ligand for reasons of steric interference.     

Conversions of 5-hydroxy-5, 6-dihydro-4H-1, 2, 5-oxadiazines

Oxidation of 5-hydroxy-5, 6-dihydro-4H-1, 2, 5-oxadiazines leads to the formation of 6H-1,2, 5-oxadiazine-5-oxides. Acid treatment of 5, 6-dihydro-4H-1, 2, 5-oxadiazines and 6H-1, 2, 5-oxadiazine-5-oxides results in heterocyclic-ring contraction with the formation of imidazole 3-oxides and 1-hydroxyimidazole 3-oxides. The structures of the products are established by their spectral properties and confirmed by independent synthesis.Translated from Khimiya Geterotsiklicheskikh Soedinenii, No. 9, pp. 1264–1266, September, 1970.     

Synthesis of 2-Amino-5-hydroxy-5-phosphonovaleric Acid

Russian Journal of General Chemistry - The synthesis of a new analog of 2-amino-5-phosphonovaleric acid (AP5), namely 2-amino-5-hydroxy-5-phosphonovaleric acid, by successive Michael addition of...     

5-Alpha- and 5-beta-2-deoxyintegristerone A,a 5-alpha and 5-beta isomer pair of ecdysteroids isolated from the Silene genus

5-Alpha-2-deoxyintegristerone A and 5-beta-2-deoxyintegristerone A were isolated from the aerial parts of Silene italica ssp. nemoralis (Waldst. and Kit.) Nyman using a specific combination of absorption column chromatography, preparative thin-layer chromatography and preparative HPLC. Both normal-phase and reversed-phase modes of HPLC were employed for isolation. Structural elucidation of 5-alpha-2-deoxyintegristerone A was completed by X-ray diffraction. Both 5-alpha-2-deoxyintegristerone A and 5-beta-2-deoxyintegristerone A were firstly isolated from this plant. We propose that 5-alpha-2-deoxyintegristerone A is not an artifact but an integral part of the ecdysteroid spectrum of Silene italica ssp. nemoralis (Waldst. and Kit.) Nyman.     

5-Fluorouracil derivative. XVII. Synthesis and antitumor activity of 5'-O-acyl-5-fluorouridines

With the aim of diminishing the toxicity of 5-fluorouridine (1) and obtaining biologically active derivatives of 1, various kinds of 5'-O-acyl-5-fluorouridines 2 were synthesized. The antitumor activity of the compounds against L-1210 leukemia in mice was examined. The 5'-O-heptanoyl derivative 2h showed the highest antitumor activity.     

5-Hydroxy-3-phenyl-5-vinyl-2-isoxazoline and 3-phenyl-5-vinylisoxazole: synthesis and reactivity

5-Hydroxy-3-phenyl-5-vinyl-2-isoxazoline has been synthesized by reacting benzonitrile oxide with the enolate ion of methyl vinyl ketone. From 5-hydroxy-5-vinyl-2-isoxazoline, 5-vinylisoxazole was then quantitatively obtained by dehydration-aromatization under acidic conditions. Similar results, though not quantitative, were also found by treatment in 2-propanol under basic conditions (i-PrOH/H₂O, Na₂CO₃, reflux). In contrast to 2-propanol, reactions performed in methanol (and, in part, those carried out in ethanol) revealed a more complex behaviour, the nucleophilic addition of ROH onto the vinyl group being mainly observed. Nucleophilic addition was also found with alkyllithiums. The mechanism of the nucleophilic addition is discussed. Epoxidation and further reaction with benzonitrile oxide of both 3-hydroxy-5-phenyl-5-vinyl-2-isoxazoline and 3-phenyl-5-vinylisoxazole are also described.     

Synthesis and properties of 5-(5-nitro-2-furyl)thiazolines

The reactions of 2-amino-4-methyl-5-(5-nitro-2-furyl)thiazole with excess methyl iodide leads to 3,4-dimethyl-2-methylamino-5-(5-nitro-2-furyl)thiazolium iodide, which is converted to 2-imino-3,4-dimethyl-5-(5-nitro-2-furyl)thiazoline under the influence of bases. The iminothiazoline structure was proved by comparison of the spectral characteristics of its acetyl derivative and the isomeric 2-(N-acetyl-N-methyl) amino-4-methyl-5-(5-nitro-2-furyl)thiazole. The pKa values of 2-amino-4-methyl-5-(5-nitro-2-furyl)thiazole and 3,4-dimethyl-2-imino-5-(5-nitro-2-furyl)-thiazoline were determined, and the constant of the aminothiazole-iminothiazoline tautomeric equilibrium was calculated.Translated from Khimiya Geterosiklicheskikh Soedinenii, No. 10, pp. 1337–1340, October, 1985.