Direct, two-step synthetic pathway to novel dibenzo[a,c]phenanthridines

Novel dibenzo[a,c]phenanthridines are prepared regioselectively by the application of a straightforward synthetic pathway, starting from new 3,4-diaryl- and 3,4-dihydro-3,4-diarylisoquinolines prepared via Ritter-type heterocyclization and the more classical two-step reductive amination/Bischler-Napieralski cyclization of triarylethanones, respectively. A comparative study of nonphenolic oxidative coupling methodologies provides a highly efficient procedure, based on the hypervalent iodine reagent phenyliodine(III) bis(trifluoroacetate) (PIFA), to accomplish the final coupling step.     

An advantageous route to oxcarbazepine (trileptal) based on palladium-catalyzed arylations free of transmetallating agents

[reaction: see text] A new route to oxcarbazepine (Trileptal), the most widely prescribed antiepileptic drug, starting from commercially available 2'-aminoacetophenone and 1,2-dibromobenzene, is reported. The sequentially accomplished key steps are palladium-catalyzed intermolecular alpha-arylation of ketone enolates and intramolecular N-arylation reactions. After several experiments to establish the best conditions for both arylation processes, the target oxcarbazepine is obtained in a satisfactory overall yield, minimizing the number of steps and employing scalable catalytic procedures developed in partially aqueous media.     

Exploring the Influence of Intermolecular Interactions in Prebiotic Chemistry Using Laser Spectroscopy and Calculations

One of the most fascinating questions in chemistry is why nature chose CGAT as the alphabet of life. Very likely, such selection was the result of multiple factors and a long period of refinement. Here, we explore how the intermolecular interactions influenced such process, by characterizing the formation of dimers between adenine, theobromine and 4-aminopyrimidine. Using a combination of mass-resolved excitation spectroscopy and DFT calculations, we determined the structure of adenine-theobromine and 4-aminopyrimidine-theobromine dimers. The binding energy of these dimers is very close to the canonical adenine-thymine nucleobases. Likewise, the dimers are able to adopt Watson-Crick conformations. These findings seem to indicate that there were many options available to build the first versions of the informational polymers, which also had to compete with other molecules, such as 4-aminopyrimidine, which does not have a valid attaching point for a saccharide. For some reason, nature did not select the most strongly-bonded partners or if it did, such proto-bases were later replaced by the nowadays canonical CGAT.     

Synthesis, crystal structure and magnetic characterization of metal(II) coordination polymers based on 2-carboxyethylphosphonic acid and 1,10-phenanthroline (metal=Cu, Co, Cd)

Three non-isostructural metal(II) coordination polymers (metal=copper, cobalt, cadmium) were synthesized under the same mild hydrothermal conditions (T=408 K) by mixture of the corresponding metal acetate with 2-carboxyethylphosphonic acid and 1,10-phenanthroline (1:1:1 M ratio) and their structures were determined by single-crystal X-ray diffraction. Cu₂(HO₃PCH₂CH₂COO)₂(C₁₂H₈N₂)₂(H₂O)₂ and Cd₂(HO₃PCH₂CH₂COO)₂(C₁₂H₈N₂)₂ are triclinic (space group P-1) with a=7.908(5) Å, b=10.373(5) Å, c=11.515(5) Å, α=111.683(5)°, β=95.801(5)°, γ=110.212(5)° (T=120 K), and a=8.162(5) Å, b=9.500(5) Å, c=11.148(5) Å, α=102.623(5)°, β=98.607(5)°, γ=113.004(5)° (T=293 K), respectively. In contrast, [Co₂(HO₃PCH₂CH₂COO)₂(C₁₂H₈N₂)₂(μ-OH₂)](H₂O) is orthorhombic (space group Pbcn) with a=21.1057(2) Å, b=9.8231(1) Å, c=15.4251(1) Å (T=120 K). For these three compounds, structural features, including H-bond network and the π-π stacking interactions, and thermal stability are reported and discussed. None of the materials present a long-range magnetic order in the range of temperatures investigated from 300 K down to 1.8 K.     

An efficient, PIFA mediated approach to benzo-, naphtho-, and heterocycle-fused pyrrolo[2,1-c][1,4]diazepines. An advantageous access to the antitumor antibiotic DC-81

[reaction: see text] The synthesis of a series of optically pure benzo-, naphtho-, and heterocycle-fused pyrrolo[2,1-c][1,4]-diazepin-5,11-dione derivatives starting from l-proline methyl ester is presented. The synthetic plan includes an aroylation step at the proline nitrogen followed by transformation of the ester residue into a N-methoxyamide group. The subsequent key cyclization step embraces the PIFA mediated formation of a N-acylnitrenium intermediate and its succeeding intramolecular trapping by the aromatic ring. The presented general approach solves the need of starting from not very accessible amino (or a related functionality) aromatic starting materials, and its effectiveness is demonstrated in the synthesis of the antitumor antibiotic DC-81.     

A lattice-theoretic approach to arbitrary real functions on frames

In this paper we model discontinuous extended real functions in pointfree topology following a lattice-theoretic approach, in such a way that, if L is a subfit frame, arbitrary extended real functions on L are the elements of the Dedekind-MacNeille completion of the poset of all extended semicontinuous functions on L. This approach mimicks the situation one has with a T₁-space X, where the lattice F?(X) of arbitrary extended real functions on X is the smallest complete lattice containing both extended upper and lower semicontinuous functions on X. Then, we identify real-valued functions by lattice-theoretic means. By construction, we obtain definitions of discontinuous functions that are conservative for T₁-spaces. We also analyze semicontinuity and introduce definitions which are conservative for T₀-spaces.     

Non-destructive characterisation of the Elephant Moraine 83227 meteorite using confocal Raman,micro-energy-dispersive X-ray fluorescence and Raman-scanning electron microscope-energy-dispersive X-ray microscopies

Analytical and Bioanalytical Chemistry - The application of a non-destructive analytical procedure to characterise the mineral phases in meteorites is a key issue in order to preserve this type of...     

3-Aryl-4-Isoquinolinone Derivatives An Efficient Oxidative Preparation

A comparative study of the oxidation of 3-aryl-4-hydroxytetrahydroisoquinolines has been carried out. A modification of the Jones conditions turn out to be the best methodology for the regioselective preparation of target 4-isoquinolinone derivatives.