Synthetic methods for γ-lactam and pyrrole derivatives exploiting a three-component coupling strategy

4-Aryloxymethyl-3-pyrrolines and their isomeric pyrrolidines--assembled via a one-pot, three-component coupling of propargylic amines, vinyl sulfones, and phenols--may be elaborated further to provide an easy access to 2,4-disubstituted pyrrole-3-carboxylates and 3,4-disubstituted pyrrolidin-2-ones. The latter were prepared by means of an unprecedented rearrangement process involving hydrogenolysis of 2-aryl pyrrolidine-3-carboxylates, whereas the pyrrole carboxylates arose from aromatization of the corresponding pyrrolines.     

Etude de l''addition des organomagnesiens satures et benzyliques aux enynes conjugues, simples et fonctionnels

Saturated and benzylic organomagnesium compounds are shown to readily undergo addition reactions with the conjugated enynes H$\text{C}\text{4}$$\text{C}\text{3}$C$\text{H}\text{2}$$\text{C}\text{1}$HCH₂R′, with R′ = alkyl, OH, OC₄H₉, NHC₂₅, N(C₂H₅)₂, by refluxing for several hours in benzene or toluene.This reaction leads to both υ-acetylenic compounds (1,2-addition) and β-allenic compounds (1,4-addition).     

Preparation et etude d'un oxyphosphate Fe4(PO4)2O

This compound is obtained in several ways, at 900°C, from the components of the FePO system when the oxygen pressure is made suitable, or from Fe₃(PO₄)₂ + Fe + Fe₂O₃ in a sealed tube under vacuum. It crystallizes under these latter conditions with a trace of FeCl₂. The cell is monoclinic; a = 6.564(1), b = 11.271(2), c = 9.383(2) Å, β = 103.95 (2)°, with Z = 4, group $\text{P2}{}_1\text{c}$. The structure is determined thanks to the use of a direct method and Fourier synthesis and is refined to R = 0.033. The PO₄ tetrahedra are isolated; the iron fills four crystallographic sites: three are more or less distorted octahedra, the fourth is a trigonal bipyramid. The oxyphosphate character is ascertained by the presence of some oxygen atoms connected to iron only, with, moreover, a low site potential. This compound is paramagnetic above 90°K. Its Mössbauer spectrum exhibits four doublets in good agreement with the structure; in order to identify which one corresponds to the hexahedral site, the phase Fe₃Zn(PO₄)₂O has been prepared, but its Mössbauer spectrum, in spite of the zinc affinity for the V coordination, shows that two sites are modified, which does not allow conclusions to be made.     

Bargaining over a climate deal: deadline and delay

Assuming that a North-South transfer is the key to effective climate cooperation, we ask when and how much the North should offer to the South in return for a commitment to reduce deforestation and forest degradation. In light of the risk of irreversible damage over time, we examine a negotiation with a deadline. In this case, the North threatens the South over a negotiation dead-end in case an agreement is not reached rapidly. We assess the conditions for an agreement to be immediate or delayed, and discuss those situations likely to result in negotiation failure. Despite the risk of irreversible damage over time, we show that cooperation is likely to be delayed and we identify situations wherein the North and South do not reach an agreement within the deadline. Although Pareto-improving, cooperation may collapse because of inefficiencies related to incomplete information. What’s more, we show that in negotiations with a deadline, uncertainty about the benefits deriving from cooperation and the irreversibility of the damage that will be caused if cooperation is delayed are the two key components affecting choice.     

Controlled Synthesis of Thorium and Uranium Oxide Nanocrystals

Very little is known about the size and shape effects on the properties of actinide compounds. As a consequence, the controlled synthesis of well‐defined actinide‐based nanocrystals constitutes a fundamental step before studying their corresponding properties. In this paper, we report on the non‐aqueous surfactant‐assisted synthesis of thorium and uranium oxide nanocrystals. The final characteristics of thorium and uranium oxide nanocrystals can be easily tuned by controlling a few experimental parameters such as the nature of the actinide precursor and the composition of the organic system (e.g., the chemical nature of the surfactants and their relative concentrations). Additionally, the influence of these parameters on the outcome of the synthesis is highly dependent on the nature of the actinide element (thorium versus uranium). By using optimised experimental conditions, monodisperse isotropic uranium oxide nanocrystals with different sizes (4.5 and 10.7 nm) as well as branched nanocrystals (overall size ca. 5 nm), nanodots (ca. 4 nm) and nanorods (with ultra‐small diameters of 1 nm) of thorium oxide were synthesised.     

Surface characterization of synthetic and mineral carbonate fluoroapatites

As part of a larger project concerning the sorption capacities of carbonate fluoroapatites, the physical and surface properties of the synthetic carbonate fluoroapatite and mineral francolite retained for this work have been carefully examined. The average particle size of the powdered samples, determined by laser granulometry, is around 30 microm. Their specific surface areas, measured according to the N(2) BET method, are 8.8+/-0.1 and 13.9+/-0.1 m(2).g(-1), respectively, for the synthetic and the mineral compound. The solubility of both solids has been studied under undersaturation initial conditions. The synthetic compound has a solubility product of 10(-103+/-2), but the mineral francolite, which is highly substituted and poorly crystalline, is more soluble and dissolves incongruently. The amphoteric properties of the hydrous carbonate fluoroapatites surfaces have also been investigated through zeta-potential measurements and potentiometric titrations in KNO(3) medium at 25 degrees C. The experimental data have been interpreted using the computer program FITEQL 3.2, applying either the nonelectrostatic or the constant capacitance model. For both solids, the values of the surface acidity constants determined with the two models are very close, suggesting a weak contribution of the electrostatic interactions. Moreover, the more acidic surface of the synthetic compound compared to that of the mineral one is assigned to the differences in crystallinity and chemical composition between the two solids.