Réactivité de spirochromènes et de mérocyanines azahétérocycliques vis-à-vis de quelques agents nucléophiles

Under the action of nucleophile reagents such as water, hydrogen sulfide and sodium borohydride, the saturated azaheterocyclic spirochromenes are opened either on the azaheterocyclic side or on the benzopyran side or on both parts simultaneously. The merocyanines are either partially reduced or decomposed by the sodium borohydride.     

Decarboxylation catalytique et quantitative d'acides arylacetiques en presence'de cuivre I

Copper(I) salts of arylacetic acids $\text{1}$ RCO₂H readily undergo a catalytic and quantitative decarboxylation in acetonitrile leading to hydrocarbons $\text{2}$ RH when the corresponding carbanions R are stabilized by resonance and/or electronwithdrawing substituents.     

Complex copper(II) fluorides. XV. The Ternary System BaF2?CuF2?ScF3

The liquid-solid phase diagram of the binary system BaF₂? ScF₃ is established by D.T.A. and radiocrystallography. Three fluorides are disclosed: Ba₃Sc₂F₁₂, Ba₅Sc₃F₁₉ and a cubic high temperature phase Ba_1?xSc_xF_2+x (x = 0.17), the structure of which derives from that of BaF₂. A solid solution between BaF₂ and ScF₃ is also evidenced at high temperature. The ternary system BaF₂? CuF₂? ScF₃ is investigated by radiocrystallography and an isothermal section at 670°C is given. It shows the existence of four phases: a complex quaternary fluoride Ba₁₀Cu₁₂ScF₄₇, two “polytypic” phases the structure of which derives from that of BaCuF₄ and a tetragonal solid solution Ba₅Sc_3?xCu_xF_19?x with 0 ≤ x ≤ 1.     

Use of uranium isotopes for the determination of river tributary flow rates: Case of the Var and the Vésubie

When a river flow rate is known on one point, it is possible to determine the one of upstream tributaries. This can be done by measuring the concentrations of a dissolved element (for example Ca²⁺), provided that no chemical precipitations have occurred in mixture waters. In this later case, the determination of flow rate is however possible by isotopic geochemistry, by knowing isotopic ratios of an element, for ex. ²³⁴U/²³⁸U, in each river considered and the ratio of the concentrations in dissolved ²³⁸U in two of them. A study of the Var and its tributary the Vésubie is performed: in January 31st, 2001, the flow rate D₃, downstream the confluence was 35 m³/s. The ratio of the ²³⁸U concentrations in the Vésubie river and in the Var upstream (²³⁸U₁/²³⁸U₂) was 5.5. The isotopic ratios ²³⁴U/²³⁸U measured in the Var, downstream the confluence were R₃ = 1.51, upstream R₂ = 1.75, and in the Vésubie R₁ = 1.08. We have calculated the Vésubie flow rate as D₁ = 3.2 m³/s.     

Synthesis of chiral N-protected 1,2-dihydro-quinoline-2-carbonitrile and 1,2-dihydro-isoquinoline-1-carbonitrile via an asymmetric Reissert reaction

Addition of cyanide ion to chiral N-acyl-quinolinium and N-acyl-isoquinolinium salts led selectively to 1,2-addition products. Removal of the chiral auxiliary affords the title compounds in pure enantiomeric form.     

Photophysical and Redox Properties of a Series of Phthalocyanines: Relation with Their Photodynamic Activities on TF-1 and Daudi Leukemic Cells

Abstract— The photodynamic therapy (PDT) efficiency of five phthalocyanines, chloroaluminum phthalocyanine (AlPc), dichlorosilicon phthalocyanine (SiPc), bis (tri- n -hexylsi-loxy)silicon phthalocyanine (PcHEX), bis (triphenyl-siloxy)silicon phthalocyanine (PcPHE) and nickel phthalocyanine (NiPc), was assessed on two leukemic cell lines TF-1 and erythroieukemic and B lymphoblastic cell lines, Daudi, respectively. AlPc showed the best photocytotox-icity leading to 0.008 surviving fraction at 2 × 10⁻⁹ M for TF-1 and 4 × 10⁻⁹ M for Daudi. At 5 × 10⁻⁷ M , SiPc and PcHEX induced a significant photokilling, whereas NiPc and PcPHE were inactive. Laser flash photolysis and photoredox properties of the phthalocyanines were investigated to try to relate these parameters with the biological effects. AlPc showed the longest triplet lifetime: 484 fis in dimethyl sulfoxide/H₂O. This value was increased up to 820 u.s when AlPc was complexed with human serum albumin used as a membrane model. Such an enhancement was not observed with the silicon phthalocyanines. Upon irradiation, all the phthalocyanines generated singlet oxygen with 0.29–0.37 quantum yield values. The reduction potentials of the excited states obtained from measurement in the ground state and energy of the excited triplets show that AlPc is the best electron acceptor. The in vitro photocytotoxicity observed and the measured parameters are in agreement with a key role of electron transfer in PDT assays involving these phthalocyanines.     

Sur diverses possibilités de formation de pyrimidines à partir de formyl-3 chromone

Guanidine transforms the following: (a) 3-formylchromone into a mixture of 2-amino-5-(2-hydroxybenzoyl)pyrimidine and 2-amino-5H-[1]-benzopyrano[4,3-d]pyrimidine; (b) the diacetate of 3-methylidyne-chromone into 2-amino-5-hydroxy-5H-[1]benzopyrano[4,3-d]pyrimidine; and (c) the oxime of 3-formylchromone into 2-amino-5H-[1]benzopyrano-[4,3-d]pyrimidin-5-one. Thiourea, acetamidine and nitroguanidine can also generate pyrimidines of the same type with 3-formylchromone, the diacetate of 3-methylidynechromone or 3-(1,3-dioxolan)chromone.     

Half-sandwich and mixed-ring uranium complexes

The monocyclooctatetraene uranium complex [U(COT)(I)₂(THF)₂] (COT=η-C₈H₈; THF=tetrahydrofuran), isolated from the reaction of bis(cyclooctatetraene)uranium with iodine, is a precursor for the synthesis of the alkyl derivatives [U(COT)(CH₂Ph)₂i (HMPA) ₂], [U(COT)(CH₂SiMe₃)₂(HMPA)] (HMPA=hexamethyl phosphorous triamide) and [U(COT)CH₂SiMe₃)₃] [Li(THF)₃] and of the mixed-ring compounds [U(COT)(η-C₅R₅)(I)] (R=H or Me). The last were used to prepare the amide and alkyl complexes [U(COT)(η-C₅H₅)(N{SiMe₃}₂)] and [U(COT)(η-C₅Me₅)(CH₂SiMe₃)].     

Synthesis of 2,3-anti-3,4-anti and 2,3-anti-3,4-syn propionate motifs: a diastereoselective tandem sequence of Mukaiyama and free-radical-based hydrogen transfer reactions

[reaction: see text] Reported herein is a strategy employing a Mukaiyama reaction in tandem with a hydrogen transfer reaction for the elaboration of 2,3-anti-3,4-anti and 2,3-anti-3,4-syn propionate motifs. The mode of complexation is controlled through monodentate or chelate pathways for the Mukaiyama reaction to give access to either syn or anti aldol products, precursors of the free-radical reduction reaction. Boron Lewis acid is used to control the free-radical reaction through the exocyclic pathway.