Palladium‐Catalysed Direct Desulfitative Arylation of Pyrroles using Benzenesulfonyl Chlorides as Alternative Coupling Partners

The reactivity of pyrrole derivatives for palladium‐catalysed desulfitative arylation has been investigated. 1‐Methyl‐, 1‐phenyl‐ and 1‐benzylpyrroles were successfully coupled with a variety of benzenesulfonyl chlorides using a phosphine‐free catalyst. Highly regioselective arylations at carbon C2 of pyrroles were observed in all cases. A wide variety of substituents on the benzenesulfonyl derivative was tolerated. It should be noted that even bromo‐ and iodo‐benzenesulfonyl chlorides were successfully coupled with pyrrole derivatives without cleavage of the C Br or C I bonds, allowing further transformations. Surprisingly, with indoles, mixtures of C2‐ and C3‐arylation products were obtained.

     

Ligand Specific Efficiency (LSE) Index for PET Tracer Optimization

Ligand efficiency indices are widely used to guide chemical optimization in drug discovery, due to their predictive value in the early steps of optimization. At later stages, however, as more complex properties become critical for success, indices relying on calculated, rather than experimental, parameters become less informative. This problem is particularly acute when developing positron emission tomography (PET) imaging agents, for which nonspecific binding (NSB) to membranes and non‐target proteins is a frequent cause of failure. NSB cannot be predicted using in silico parameters. To address this gap, we explored the use of the experimentally determined chromatographic hydrophobicity index on immobilized artificial membranes, CHI(IAM), to guide the optimization of NSB. The ligand specific efficiency (LSE) index was defined as the ratio between affinity (pIC₅₀ or pK_d) and the logarithmic value of CHI(IAM). It allows for quantification of binding affinity to the target of interest, relative to NSB. Its use was illustrated by the optimization of PET tracer candidates for the prostacyclin receptor.     

CdTe solar cell with industrial Al:ZnO on soda-lime glass

One avenue to enhance CdTe cell performance is to improve the optical transmission of the transparent conductive oxide (TCO)/window layer stack. In this paper, we examine soda-lime float glass coated with an Al-doped ZnO layer and a buffer layer. The possible advantages of using a ZnO-based TCO include reduced surface roughness, improved transparency, and an integrated buffer layer that can be optimized for use in a CdTe PV device. Device processing was modified to address the chemical and thermal differences between the ZnO-based TCO stack produced by Saint-Gobain and the TCOs previously used at the National Renewable Energy Laboratory (NREL). These process modifications produced ~ 8% efficiency for devices without a buffer layer. Incorporation of buffer layers has already produced devices with ~ 11% and > 12% efficiency for CdTe deposition temperatures of 570° and 500°C, respectively.     

Characterization of conducting polymers by inverse gas chromatography Part II. Effect of dopant on the dispersive and specific properties of polypyrrole

A series of polypyrroles, synthesized using iron(III) oxidizing agent, was characterized by inverse gas chromatography (IGC). The dispersive component to the surface tension of these materials falls in the range 40–60 mJ/m² for Cl⁻- and NO₃⁻-doped polypyrroles, whereas that of Fe(CN)₆⁻ is extremely high (106 mJ/m²) when compared to a conventional polymer. These values rank conducting polypyrroles between conventional insulating polymers and high surface energy materials such as metals, metal oxides and graphite. In addition, all polymers exhibit strong specific adsorption of acidic and basic molecular probes, confirming the Lewis amphoteric behaviour of conducting polypyrroles. The hard and soft acids and bases (HSAB) concept is also emphasized in an original manner based on acidic and basic Lewis probes and in connection with the nature of the dopant. This IGC study shows that the dopant plays an important role in the surface thermodynamics of conducting polypyroles, as evidenced by the magnitude of the dispersive and acid-base properties.     

XV. Yeast sequencing reports. Sequence of a 10·27 kb segment on the left arm of chromosome XV from Saccharomyces cerevisiae includes part of the IRA2 gene and a putative new gene

A 10 270 bp fragment from the left arm of chromosome XV of Saccharomyces cerevisiae was sequenced and analysed. The sequence reveals the presence of two open reading frames (ORFs), one of them is the larger part of the previously sequenced gene IRA2 (YOL0951). The other ORF, YOL0950, has a length of 1245 nucleotides and exhibits no significant homology with any known gene, although there is some similarity of its upstream region to the corresponding region of the Schizosaccharomyces pombe cdr1/nim1 gene which is involved in the control of mitotic cell size. The sequence has been deposited in the EMBL data library under Accession Number X75449.     

Characterisation of genuine and derived cranberry proanthocyanidins by LC–ESI-MS

Cranberry proanthocyanidins (PACs) were characterised by HPLC (after thiolysis) and LC–ESI-MS analysis after fractionation by normal-phase chromatography. According to the HPLC retention time and mass spectra of compounds released after depolymerisation reaction, PACs are based on epicatechin and dimer A2 units along with catechin (minor component) and epigallocatechin (trace amounts). Fractionation at semi-preparative scale on normal phase allowed to remove other phenolic compounds than PACs (flavonols, phenolic acids and anthocyanins) and to separate the PACs according to their polymerisation degrees. Six fractions were eluted. PAC concentration, mean degree of polymerisation and percentage of A-type bonds were calculated for these six fractions by HPLC after thiolysis. Whereas the three first fractions contained phenolic acids and flavonols, the three latest fractions were enriched in PACs. Genuine PACs (A and B-types) from DP2 to DP16 were detected by LC–DAD-ESI-MS analysis. Fragmentation on ion trap spectrometer allowed us to determine the position of A-type bonds. Derived PACs were also observed: anthocyanin ethyl-bridged PACs (monomer to tetramer) in the three last fractions, flavonol-ethyl-PACs (monomer and dimer) in the third fraction and pyranoanthocyanin derivatives in the last fraction.     

Capture and corruption in public utilities: The cases of water and electricity in Sub-Saharan Africa

The paper focuses on public utilities services located in poor countries with a special attention to capture and corruption issues. It confronts the optimal policy of Auriol and Picard [Privatization in Developing Countries and the Government Budget Constraint, Nota di Lavoro 75.2002. Fondazione Eni Enrico Mattei, Milan, Italy] regarding private sector involvement in public utilities with empirical evidence on water and electricity in Sub-Saharan Africa (SSA). As predicted by the theory, the participation of private unregulated firms in the supply of services for the middle class and poor people is fairly common in SSA. By contrast, services for rich people are provided by public utilities. Theory suggests that their prices should be high so that the public firms make a profit. Yet piped water and electricity are subsidized. This suggests that there is a problem of capture by the ruling elite. Since ruling elites design privatization programs, there is concern about their optimality. The paper shows that the social cost of corrupted privatization is non-monotone in the opportunity cost of public funds. Because of the fiscal loss it represents, privatizing profit centers of public firms entails huge social costs in very poor countries.