Inclusion Complexes of β-Cyclodextrin with Keto/Enol Tautomers of 2-Acetyl-1-tetralone. A Comparative Study

The keto–enol interconversion of 2-acetyl-1-tetralone (ATLO) and of 2-acetyl-cyclohexanone (ACHE) occurs at measurable rates in aqueous acid or neutral medium. This finding allowed us to determine the keto–enol equilibrium constants, K _E, by following two distinct methods. Both methodologies afford results in complete agreement. The first one is a test of the Beer-Lambert law under two different experimental conditions that contain the substrate only in the enol form or in a mixture of both tautomers in equilibrium. The second method analyses the UV-absorption spectrum of each substrate under keto–enol equilibrium in aqueous β-cyclodextrin (β-CD) solutions of variable concentration: the presence of β-CD increases the percentage of the enol due to the formation of 1:1 inclusion complexes between this tautomer and β-CD. Rates of keto–enol tautomerization, in neutral and acid medium, and of nitrosation in acid medium under non equilibrium conditions have also been measured. Throughout the study, the presentation of the results is done by comparing the different behaviour observed between ATLO and ACHE. While the enol of ACHE included into the β-CD cavity shows to be unreactive either in tautomerization or in nitrosation, in the case of ATLO it is observed tautomerization through the complexed enol. In addition, with ACHE only the enol tautomer forms inclusion complexes with β-CD, whereas with ATLO the keto tautomer entries also to the β-CD cavity, however the stability constant with the enol is near 3-fold that of the keto isomer. These main differences can be rationalized on the basis of the molecular structure of these diketones.This revised version was published online in July 2005 with a corrected issue number.     

Synthesis of functionalized 3,4-dihydro-2H-pyrans by hetero —Diels-Alder reaction of an enaminoketone with enol ethers

Summary The hetero —Diels-Alder reaction of 3-(N-acetylbenzylamino)-2-cyano-1-phenyl-2-propen-1-one (3) with enol ethers (4) leads to diastereoisomeric cycloadducts5 and6 in good yields. The structure of the products is discussed in terms of configuration and preferred conformation. Reaction of5 with sulfuric acid yields 3-benzoyl-1,2-dihydropyridin-2-one (7).

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Synthese funktionalisierter 3,4-Dihydro-2H-pyrane durch Hetero —Diels-Alder — Reaktion eines Enaminoketons mit Enolethern

Zusammenfassung Die Hetero —Diels-Alder — Reaktion von 3-(N-Acetylbenzylamino)-2-cyano-1-phenyl-2-propen-1-on (3) mit Enolethern (4) führt in guten Ausbeuten zu den diastereomeren Cycloaddukten5 und6. Die Strukturen der Produkte werden im Zusammenhang mit ihrer Konfiguration und Vorzugskonformation diskutiert. Die Reaktion von5 mit Schwefelsäure liefert 3-Benzoyl-1,2-dihydropyridin-2-on (7).

     

Structural and spectroscopic characteristics of α-cyano-substituted α-phosphoryl(thiophosphoryl)acetonates in neutral chelate-bridged complexes. Crystal structure of [Cu[(PrO)2P(O)C(CN)C(Me)O]2]

A comparative study of the three-dimensional and electronic structures of the chelate salts (ML _n ) of enol forms of -cyano-substituted -phosphoryl- and -(thiophosphoryl)acetones (RO)₂P(X)C(CN)C=CMe(OH) (X = O or S; R = Pr or Et) with the Cu^I, Cu^II, and Co^II cations was carried out. In all complexes under consideration, the geometry of the central moiety of the O—C(Me)—C(CN)—P chelate-bridging ligand remains unchanged. The substantial electron delocalization involving the cyano group is observed in the O—C—C(CN)—P(X) ligand framework. The structure of the bis-chelate Cu[(PrO)₂P(O)C(CN)C(O)Me]₂ complex was established by X-ray diffraction analysis at 180 K and vibrational (IR and Raman) spectroscopy. The study in the temperature range from 290 to 140 K revealed the phase transition at 200 K accompanied by a change in the coordination polyhedron about the copper cation from a symmetrical octahedron (4+2 coordination) to a strongly unsymmetrically distorted octahedron (4+1+1 coordination). In both crystal modifications, four oxygen atoms form the base of the octahedron, and the axial positions are occupied by the nitrogen atoms.     

The N—H and O—H bond dissociation energies in 4-hydroxydiphenylamine and its phenoxyl and aminyl radicals

The N—H and O—H bond dissociation energies in 4-hydroxydiphenylamine Ph—NH—C₆H₄—OH (D _NH= 353.4, D _OH=339.3 kJ mol^–1) and its semiquinone radicals D _NH(Ph—NH—C₆H₄—O^·) = 273.6, D _OH(Ph—N^·—C₆H₄—OH) = 259.5 kJ mol^–1 were first estimated using the parabolic model and experimental data (rate constants) on two elementary reactions with participation of N-phenyl-1,4-benzoquinonemonoimine (2). One of the reactions, namely, that of 2 with aromatic amines, was studied in this work using a specially developed method.     

Fluorinated 1,3-diketones, 2-trifluoroacetyl phenols and their derivatives: versatile reactants in phosphorus chemistry

The role of fluorinated β-diketones, their tautomers (keto–enols) and their derivatives as reagents towards λ³P compounds is reviewed, including 2-trifluoroacetyl phenols, possessing formally a keto–enol system, and their derivatives. In an ‘insertion’ reaction phosphine and the keto–enol tautomers of 1,1,1,5,5,5-hexafluoro- and 1,1,1-trifluoropentan-2,4-dione furnished primary (S) or (R) α-hydroxy phosphines, whose enol functions probably isomerized the corresponding keto compounds. Further addition and isomerisation furnished 1,3α,5,7β-tetrakis(trifluoromethyl)-2-phospha-6-oxa-9-oxabicyclo[3.3.1]-nonan-3β,7α-diol and 1,7-trifluoromethyl-3,5-methyl-2,4,8-trioxa-6-phophaadamantane, exclusively one diastereomer in each case. The main mechanistic feature of these reactions is a consecutive diastereoselective hemiketal cyclization. 1,1,1,5,5,5-Hexafluoro- and 1,1,1-trifluoropentan-2,4-dione, as well as 2-trifluoroacetyl phenol and its imino derivatives reacted diastereospecifically with phosphonous acid dichlorides, RPCl₂ to give in a concerted mechanism thermally stable tricyclic λ⁵σ⁵P phosphoranes containing two five-membered rings and one six-membered ring. Surprisingly, the two CF₃ groups bonded to an sp³-hybridized carbon were in a cisoid arrangement having closest non-bonding FF distances of 301.4 or 273.5 pm. These findings reflect the ‘through space’ F---F coupling constants of the tricyclic phosphoranes (J_FF=4.0–7.0 Hz), in solution. 4,4,4-Trifluoro-3-hydroxy-1-phenyl-butan-1-one and methyl or phenyl phosphonous acid dichlorides gave similar tricyclic phosphoranes decomposing at ambient temperature to furnish 1,2λ⁵σ⁴-oxaphospholanes and (E)-1,1,1-trifluoro-4-phenyl-but-2-en-4-one. Dialkylphosphites and 1,1,1,5,5,5-hexafluoropentan-2,4-dione reacted to give either the (Z)-enol phosphonates or the respective γ-ketophosphonates from which in two cases four diastereomeric 2-oxo-2,5-dialkoxy-3,5-bis(trifluoromethyl)-3-hydroxy-1,2λ⁵σ⁴-oxa-phospholanes were obtained. 2-Trifluoroacetyl cyclohexanone, 4,4,4-trifluoro-3-trimethylsiloxy-1-phenylbutan-1-one, 1-benzoyl-2-trifluormethyloxirane, 1-benzoyl-2-trifluoro-methylaziridine, 2-trifluoroacetyl-1-trimethylsiloxybenzene and (trifluoroacetyl-1-phenyl) diethyl phosphate reacted with tris(trimethylsilyl) phosphite to give functionalized α-trimethylsiloxy phosphonates, which could easily be transferred into the respective phosphonic acids. In the case of an oxirane and an aziridine ketone no ring cleavage was observed. For 1,1′-(2-hydroxy-5-methyl-m-phenylene)-bis-ethanone and 1,1′-(2-trimethylsiloxy-5-methyl-m-phenylene)-bis-ethanone benzoxaphospholanes were obtained. Trialkyl phosphites and 1,1,1,5,5,5-hexafluoropentan-2,4-dione furnished cyclic phosphoranes containing the 3-hydroxy-3,5-bis(trifluoromethyl)-1,2λ⁵σ⁵-oxaphospholene structural element, stable at ambient temperature only in the case of one cyclic phosphite precursor. (E)-1,1,1-Trifluoro-4-phenyl-but-2-en-4-one and trimethylphosphite reacted to form 1,2λ⁵σ⁵-oxaphosphol-4-ene as the sole product. Results similar to the reaction of 1,1′-(2-hydroxy-5-methyl-m-phenylene)-bis-ethanone with diethyltrimethylsilylphosphite were obtained for trimethylphosphite and 2-trifluoroacetyl phenol where a deoxygenated phosphorane was found, easily hydrolyzed to give the respective phosphonic acid. With dialkylisocyanato phosphites and the keto components, 1,1,1,5,5,5-hexafluoro- and 1,1,1-trifluoropentan-2,4-dione, 4,4,4-trifluoro-1-phenyl-1,3-butandione, 2-trifluoroacetyl cyclohexanone, 2-trifluoroacetyl phenol and 1,1′-(2-hydroxy-5-methyl-m-phenylene)-bis-ethanone reacted in a ‘double’ cycloaddition to form bicyclic phosphoranes containing the 4,8-dioxa-2-aza-1λ⁵σ⁵-phosphabicyclo[3.3.0]-oct-6-en-3-one ring system; for the imino derivatives of 2-trifluoroacetyl phenol a corresponding 8-oxa-2,4-diaza- system was generated. For (E)-1,1,1,5,5,5-hexafluoro-4-trimethylsiloxy-3-penten-2-one however, a cyclic spiroimino phosphorane was obtained which underwent a [2+2] cyclodimerization to form a diazadiphosphetidine. Dimethylpropynyl phosphonite and 1,1,1,5,5,5-hexafluoropentan-2,4-dione yielded diastereoselectively a bisphosphorane, namely 1,4-bis(trifluoromethyl)-3,6-dioxa-2,2,7,7-tetramethoxy-2,7-di(1-propynyl)-2,7-diphosphabicyclo[2.2.1] heptane. When trimethylsilanyl–phosphenimidous acid bis-trimethylsilanyl–amide, Me₃SiN=PN(SiMe₃)₂, was allowed to react with 1,1,1,5,5,5-hexafluoro- and 1,1,1-trifluoropentan-2,4-dione, (E)-1,1,1,5,5,5-hexafluoro-4-trimethylsiloxy-3-penten-2-one, 2-trifluoroacetyl cyclopentanone, 2-trifluoroacetyl phenol and its imino derivatives, 2-imino-1,2λ⁵σ⁴-oxaphospholenes were found containing two diastereomers in each case, which added hexafluoroacetone across the P=N bond to give 1,3,2λ⁵σ⁵-oxazaphosphetanes.     

Pd-catalyzed asymmetric allylation of an o-carborane derivative

The asymmetric synthesis of methyl 2-phenyl-2-(2-phenyl-ortho-carboran-1-yl)pent-4-enoate was carried out by palladium-catalyzed allylation in the presence of amino phosphites of the type (RO)₂P—O—CH₂—CHR"—NR₂ as chiral ligands.     

Synthesis,characterization and antimicrobial activity of cobalt(II), nickel(II)and copper(II) complexes with new asymmetrical Schiff base ligands derived from 7-formyanil-substituted diamine-sulphoxine and acetylacetone

Asymmetric 7-formyanil-substituted-imino-4-(4-methyl-2-butanone)-8-hydroxyquinoline-5-sulphonic acid (Schiff bases), react with Co^II, Ni^II and Cu^II ions to give 1:2, 1:1 and 2:1 complexes as established by conductometric titrations in 1:1 DMF:H₂O. The complexes were investigated by elemental analyses, molecular weight determinations, molar conductance, magnetic moments, thermal analysis, i.r., u.v.–vis. and e.s.r. spectra. The complexes have an octahedral crystal structure and general formula [ML·(OH₂)₂], where M^II = Co, Ni and Cu, and L = Na[7—X—HL], (—X— = (CH₂)₂, (CH₂)₃, p-C₆H₄, o-C₆H₄). Antimicrobial activity of these new ligands and their transition metal complexes has been screened in vitro on common fungi and bacteria.     

Syntheses,crystal structures and magnetic properties of two cyano-bridged two-dimensional assemblies [Fe(salpn)]2 [Fe(CN)5NO] and [Fe(salpn)]2[Ni(CN)4]

Two cyano-bridged assemblies, [Fe^III(salpn)]₂[Fe^II(CN)₅NO] (1) and [Fe^III (salpn)]₂[Ni^II(CN)₄] (2) [salpn = N, N-1,2-propylenebis(salicylideneiminato)dianion], have been prepared and structurally and magnetically characterized. In each complex, [Fe(CN)₅NO]^2– or [Ni(CN)₄]^2– coordinates with four [Fe(salpn)]⁺ cations using four co-planar CN^– ligands, whereas each [Fe(salpn)]⁺ links two [Fe(CN)₅NO]^2– or [Ni(CN)₄]^2– ions in the trans form, which results in a two-dimensional (2D) network consisting of pillow-like octanuclear [—M^II—CN—Fe^III—NC—]₄ units (M = Fe or Ni). In complex (1), the NO group of [Fe(CN)₅NO]^2– remains monodentate and the bond angle of Fe^II—N—O is 180.0°. The variable temperature magnetic susceptibilities, measured in the 5–300 K range, show weak intralayer antiferromagnetic interactions in both complexes with the intramolecular iron(III)iron(III) exchange integrals of –0.017 cm^–1 for (1) and –0.020 cm^–1 for (2), respectively.     

Glycosylated vinyl ethers by the Julia–Lythgoe–Kocienski olefination: application to the synthesis of 2′,5′-dideoxydisaccharides and carbohydrated β-lactams

α-Carbohydrated pyridinyl sulfones, prepared from commercially available d-(−)-ribose, d-(+)-galactose, and d-(+)-glucose through a five-step sequence, have been employed in the Julia–Lythgoe–Kocienski olefination with aldehydes. This one-pot protocol, using solid KOH at room temperature, affords the corresponding glycosidic enol ethers in moderate to excellent yields and (E)-stereoselectivities. These glycosylated adducts undergo hetero-Diels–Alder reactions with 2-formyl-1-malondialdehyde to afford 2′,5′-dideoxygenated disaccharides in good yields and complete regio- and endo-selectivity. Alternatively, the [2+2]-cycloaddition reaction of the glycosidic enol ethers with chlorosulfonyl isocyanate provided glycosylated β-lactams regioselectively and with only trans-stereoselectivity. The β-lactams could be converted to N-methylthio derivatives which show decent antibacterial activity toward methicillin-resistant strains of Staphylococcus aureus.     

An Improved Method for the Preparation of Tetra-Coordinate Platinum(II) Chloro-Complexes Containing Bidentate or Terdentate Ligands Starting from cis/trans-[PtCl2(SMe2)2]

An improved method for the preparation of differently charged chelate Pt(II) chloro-complexes is reported. All the complexes have been obtained rapidly and in high yield, by simply reacting equimolar amounts of cis/trans- dichlorobis(dimethylsulphide)platinum(II) with the chelate ligand in an appropriate solvent (CH₂Cl₂, MeOH or H₂O). The ligands chosen were: 1,2-bis(diphenylphosphino)ethane (P—P), pyridine–2-carboxylate (N—O⁻), 2-[(methylthio)methyl]pyridine (N—S), 1,10-phenanthroline (N—N), bis(2-pyridylmethyl)sulphide (N—S—N), di-(2-picolyl)amine (N—N—N), pyridine-2,6-dicarboxylate (O—N—O²⁻) and 2,6-bis(methylthiomethyl)pyridine (S—N—S).     

B—Z bond dissociation energies of <Emphasis Type="Italic">para</Emphasis>-substituted phenylboranes: a problem for Nau's definition of polar ground-state effects

UB3LYP/6-311++g(2df,p) and RMP2/6-311++g(d,p) methods were used to calculate B—Z bond dissociation energies (BDE) of para-substituted phenylboranes (X—C₆H₄—BH—Z). It was found that the slopes () of regressions between B—Z BDEs and substituent _p constants increase in the order B—Cl (between –0.24 and 0.21 kcal/mol) < B—H (0.06-0.33 kcal/mol) < B—F (0.48-0.78 kcal/mol) < B—CH₃ (0.83–1.28 kcal/mol) < B—Li (2.62-3.73 kcal/mol). Since all the homolysis reactions give the same boron radical, the large variation of indicates that the substituent effects on energies of the ground-state molecules are important for the substituent effects on BDEs. However, the ground-state stabilization energies, calculated using either Nau's method or our method, do not show any correlation with the polarization of the B—Z bond as defined by the electronegativity difference between the group X—C₆H₄—BH and Z. Therefore, the theory that the remote substituent effects on Y—Z BDEs are dependent on the Y—Z polarity should be discarded.     

1,3-Dipolar cycloaddition of diazomethane and diazocyclopropane to 2-fluoro-3-methylbutadiene and thermal transformations of fluorine-containing vinylpyrazolines and vinylcyclopropanes

Reactions of 2-fluoro-3-methylbuta-1,3-diene with diazomethane in ether at 15 °C and with diazocyclopropane generated in situ by decomposition of N-cyclopropyl-N-nitrosourea in the presence of K₂CO₃ in CH₂Cl₂ at –10 °C selectively involve the double bond at the methyl group to give 3-(1-fluorovinyl)-3-methylpyrazolines. Thermal dediazotization of the latter at 250 °C yields 1-(1-fluorovinyl)-1-methylcyclopropane and -spiropentane 5, which are capable of isomerizing, under more severe conditions (400—600 °C), into 1-fluoro-2-methylcyclopent-1-ene and 5-fluoro-4-methylspiro[2.4]hept-4-ene (7), respectively. Spiropentane derivative 5 partially isomerizes into 1-fluoro-2-methyl-3-methylidenecyclohex-1-ene. In a similar way, thermolysis of 6-(2,3,3-trifluorocyclobut-1-enyl)-4,5-diazaspiro[2.4]hept-4-ene at 400 °C gives a mixture of 1-(spiropentyl)-2,3,3-trifluorocyclobut-1-ene and 2,3,3-trifluoro-1-(2-methylidenecyclobutyl)cyclobut-1-ene. Thermolysis of 1-cyclopropyl-2,3,3-trifluorocyclobut-1-ene at 550—620 °C affords a mixture of 1-(trifluorovinyl)cyclopentene and 2,3-difluorotoluene.     

Functionalization of the Methyl Ketone Fragment in 1-[(1S,3R)-2,2-Dimethyl-3-(2-methoxymethyloxyethyl)cyclopropyl]-2-propanone

Deprotonation of 1-[(1S,3R)-2,2-dimethyl-3-(2-methoxymethyloxyethyl)cyclopropyl]-2-propanone with lithium diisopropylamide in THF at -78°C and subsequent treatment of the resulting enolate with Me₃SiCl yielded mainly the corresponding terminal silyl enol ether. The condensation of intermediate enolate with benzaldehyde regioselectively afforded a mixture of the corresponding aldol and its dehydration product. The reactions of the title ketone with NBS, as well as of the silyl enol ethers derived therefrom with I₂, led to formation of mixtures of products via opening of the cyclopropane ring.     

Photochemical and thermal transformations of diazo derivatives of 1-aryloxy- and 1-arylthio-2-aminoanthraquinones

In the photochemical and thermal decomposition of diazonium derivatives of 1-aryloxy- and 1-arylthio-2-aminoanthraquinones in CH ₃ COOH and dioxane, high yields of intramolecular arylation products — anthra-[2, 1-d]-4-tert-butylbenzo-[b]-furan-and anthra-[2, 1-d]-4-tert-butylbenzo-[b]-thiophene-8,13-diones — are formed. It was established that 2-azo derivatives of 1-aryloxy- and 1-acyloxyanthraquinones synthesized on the basis of the diazonium salts are stable under photolysis conditions.Novosibirsk Institute of Organic Chemistry, Siberian Branch, Russian Academy of Sciences, Novosibirsk 630090. Translated from Izvestiya Akademii Nauk, Seriya Khimicheskaya, No. 3, pp. 582–585, March, 1992.     

The ternary system cerium–palladium–silicon

Phase relations in the ternary system Ce–Pd–Si have been established for the isothermal section at 800 °C based on X-ray powder diffraction and EMPA techniques on about 130 alloys, which were prepared by arc-melting under argon or powder reaction sintering. Eighteen ternary compounds have been observed to participate in the phase equilibria at 800 °C. Atom order was determined by direct methods from X-ray single-crystal counter data for the crystal structures of τ₈—Ce₃Pd₄Si₄ (U₃Ni₄Si₄-type, Immm; a=0.41618(1), b=0.42640(1), c=2.45744(7) nm), τ₁₆—Ce₂Pd₁₄Si (own structure type, P4/nmm; a=0.88832(2), c=0.69600(2) nm) and also for τ₁₈—CePd_1−xSi_x (x=0.07; FeB-type, Pnma; a=0.74422(5), b=0.45548(3), c=0.58569(4) nm). Rietveld refinements established the atom arrangement in the structures of τ₅—Ce₃PdSi₃ (Ba₃Al₂Ge₂-type, Immm; a=0.41207(1), b=0.43026(1), c=1.84069(4) nm) and τ₁₃—Ce_3−xPd_20+xSi₆ (0≤x≤1, Co₂₀Al₃B₆-type, Fm3¯m; a=1.21527(2) nm). The ternary compound Ce₂Pd₃Si₃ (structure-type Ce₂Rh_1.35Ge_4.65, Pmmn; a=0.42040(1), b=0.42247(1), c=1.72444(3) nm) was detected as a high-temperature compound, however, does not participate in the equilibria at 800 °C. Phase equilibria in Ce–Pd–Si are characterized by the absence of cerium solubility in palladium silicides. Mutual solubility among cerium silicides and cerium–palladium compounds are significant whereby random substitution of the almost equally sized atom species palladium and silicon is reflected in extended homogeneous regions at constant Ce-content such as for τ₂—Ce(Pd_xSi_1−x)₂ (AlB₂-derivative type), τ₆—Ce(Pd_xSi_1−x)₂ (ThSi₂-type) and τ₇—CePd_2−xSi_2+x. The crystal structures of compounds τ₄—Ce_~8Pd_~46Si_~46, τ₁₂—Ce_~29Pd_~49Si_~22, τ₁₅—Ce_~22Pd_~67Si_~11, τ₁₇—Ce_~5Pd_~77Si_~18 and τ₁₈—CePd_1−xSi_x (x~0.1) are still unknown.     

Synthesis of potential antineoplastics by condensation of phthalic anhydride with 4-bis(2-chloroethyl)aminophenylacetic acid

Indandione, its enol acetate, and the products of a parallel reaction — a mixture of isomeric acidsE, Z-5, and phthalide — are formed in the reaction of substituted phenylacetic acid with phthalic anhydride in acetic anhydride and triethylamine. 2-Substituted indandione derivatives were obtained.N. N. Semenov Institute of Chemical Physics, Russian Academy of Sciences, 117977 Moscow. Institute of Chemical Physics in Chernogolovka, Russian Academy of Sciences, 142432 Chernogolovka. Translated fromIzvestiya Akademii Nauk, Seriya Khimicheskaya, No. 11, pp. 2609–2617, November, 1992.     

1, 5-Rearrangement of enol acylates of aryl 1H.-1, 2, 4-triazol-1-ylmethyl ketones

The rearrangement of enol acylates of aryl 1H-1, 2, 4-triazol-1-ylmethyl ketones at 140–150°C in acetic anhydride is studied. The migration of the acyl group to the C(5) atom of the heterocycle is found to be intramolecular. The characteristics of the original and final products are presented. X-ray structural studies of the enol acetates of 2, 4-dichlorophenyl 1H-1, 2, 4-triazol-1-ylmethyl ketone and 2, 4-dichlorophenyl 5-acetyl-1H-1, 2, 4-triazol-1-ylmethyl ketone are carried out.Translated fromIzvestiya Akademii Nauk. Seriya Khimicheskaya, No. 3, pp. 560–564, March, 1993.     

Site-specific modification of the 5"-terminal fragment of PGY1/MDR1 gene mRNA by reactive conjugates of antisense oligonucleotides

The site-specific modification of the 5"-terminal fragment of PGY1/MDR1 mRNA by oligodeoxyribonucleotide conjugates bearing residues of bleomycin A₅ (Blm), cobalt(ii) tetracarboxyphthalocyanine (Phcn), 4-[N-(2-chloroethyl)-N-methylamino]benzylamine (RCl), or perfluoroarylazide (Az) was studied. Conjugates of oligonucleotides complementary to the RNA sequences 123—138 and 155—166 selectively modify RNA in the vicinity of these regions. The highest efficacy (up to 50%) was achieved in reactions with alkylating and perfluoroarylazide conjugates of oligonucleotides. Conjugates of perfluoroarylazide with 2"-O-modified oligonucleotides are much more efficient than analogous conjugates with oligodeoxyribonucleotides (extents of RNA modification are 40—50% and 20%, respectively).     

Thiolato-technetium complexes. 4(1): Synthesis,characterization and electrochemical properties of bis(1,2-bis(dimethylphosphino)-ethane)technetium(III) complexes with arene-thiolato ligands

Summary The reaction of trans-[Tc^v(OH)(O)(DMPE)₂]²⁺ (DMPE = 1,2-bis(dimethylphosphino)ethane) with a series of arenethiols in base produces the novel complexes cis-[Tc^III-(SC₆H₄X-p)₂ (DMPE)₂]⁺ for X = H, Cl, Me, OMe, t-Bu. One of the complexes has been characterized by X-ray crystallography: cis-[Tc(SPh)₂(DMPE)₂]PF₆, chemical formula Tc₁S₂P₅F₆C₂₄H₄₂, crystallizes in the orthorhombic space group P2₁nb with Z = 4 and lattice parameters a = 9.311(1) Å, b=11.190(2) Å, c = 31.936(4) Å, Vol = 3327.3(8) ų. The final weighted R-value was 0.033. Averaged structural parameters are Tc—S = 2.29(2) Å, Tc—P (trans to P) = 2.42(1) Å, Tc—P (trans to S) = 2.49(3) Å, Tc—S—C = 118.5(5)°. The complexes have been characterized by FAB mass spectrometry and u.v.-vis. spectroscopy. The visible region charge transfer bands are diagnostic for cis geometry in the [Tc(SR)₂(DMPE)₂]⁺ complexes. Electrochemical and spectroelectrochemical measurements show reversible Tc^III/II redox couples in the range -0.19V to -0.38V versus Ag/AgCl (3 M NaCl). Irreversible couples are exhibited at ca. -1.1 V to -1.2 V for Tc^II/I and +0.7V to +0.9V for Tc^IV/III. Variation in redox potential is discussed in terms of sulphur nucleophilicity.On leave from the Department of Chemistry, The University of Tsukuba, Tsukuba, Ibaraki 305, Japan.On leave from Dipartimento di Chimica dell'Universita' di Sassari, Via Vienna, 2-Sassari, Italy.     

Synthese von 2-Methylen-2,3-dihydro- und 2-Methyl-5H-thiazolo[3,2—a]thieno[2,3—d]pyrimidinen

The title substances and their [1]benzothieno analogues were synthesized by reaction of 3-allyl-2-mercapto-([1]benzo)thieno-[2.3—d]pyrimidine-4(3H)-ones with Br₂ to 2-bromomethyl-2.3-dihydro-thiazolo[3.2—a]([1]benzo-)thieno[2.3—d]pyrimidine-5-ones, which on treatment with morpholine did not give the corresponding morpholine derivatives but elimination to the exocyclic double bond. These 2-methylene-2.3-dihydro-products were isomerized by H₂SO₄ to the corresponding 2-methyl compounds.