Clathrate formation from octaazaphthalocyanines possessing bulky phenoxyl substituents: a new cubic crystal containing solvent-filled, nanoscale voids

The synthesis of octaazaphthalocyanine (AzaPc) derivatives, with bulky phenoxyl substituents placed at eight peripheral positions and containing either H(+), Ni(2+) or Zn(2+) ions in their central cavity, is described. The required precursors, derivatives of pyrazine-2,3-dicarbonitrile, were prepared using a nucleophilic aromatic substitution reaction between 2,6-diisopropylphenol or 2,6-diphenylphenol and 5,6-dichloropyrazine-2,3-dicarbonitrile. Analysis of the resulting AzaPcs by UV/Visible and (1)H NMR spectroscopy confirms that steric isolation of the AzaPc cores was enforced both in solution and in the solid state. X-ray diffraction studies of single crystals of the AzaPcs reveal that solvent inclusion takes place in each case. Of particular significance is the finding that the zinc derivative of 2,3,9,10,16,17,23,24-octa-(2,6-diisopropylphenoxy)octaazaphthalocyanine provides nanoporous cubic crystals, containing massive (8 nm(3)) solvent-filled voids, similar to those of the analogous phthalocyanine derivative. Exchange of the included solvent within the voids can be readily achieved by using a number of alternative solvents including water. Based on the observed loading of included water, the internal volume of this nanoporous cubic crystal appears to be more hydrophilic than its phthalocyanine counterpart.     

The search for a potentially prebiotic synthesis of nucleotides via arabinose-3-phosphate and its cyanamide derivative

For the RNA world hypothesis to be accepted, the constitutional self-assembly of RNA will have to be demonstrated. Conceptually, the simplest route to RNA involves nucleotide polymerisation. Activated pyrimidine nucleotides can be derived from arabinose-3-phosphate under potentially prebiotic conditions, but the prebiotic synthesis of this sugar phosphate has not hitherto been investigated. The results of synthetic approaches involving phosphorylation, phosphate migration and 2,3-C--C bond construction are described herein.     

Ligand influence on the formation of P/Se semiconductor materials from metal-organic complexes

The complexes [Ni{(SeP(i)Pr(2))(2)N}(2)] (), [Ni(Se(2)P(i)Pr(2))(2)] (), and [Co(Se(2)P(i)Pr(2))(2)] () were synthesised and the X-ray single crystal structures of () and () were determined. Thin films of nickel selenide, cobalt selenide and cobalt phosphide have been deposited by the chemical vapour deposition method using imidodiselenophosphinato-nickel(ii) (), -cobalt(ii) [Co{(SeP(i)Pr(2))(2)N}(2)] (), diselenophosphinato-nickel(ii) (), -cobalt(ii) () and diselenocarbamato-nickel(ii) [Ni(Se(2)CNEt(2))(2)] (), and -cobalt(iii) [Co(Se(2)CNEt(2))(3)] () precursors.     

Chemical communication: conductors and insulators of screw-sense preference between helical oligo(aminoisobutyric acid) domains

(1)H NMR studies quantify the abilities of achiral amino acids to communicate a left-handed screw-sense preference from one helical Aib(4) domain to another: certain quaternary amino acids (e.g. Ac(6)c) act as effective conductors of conformational preference while others (e.g. diphenylglycine) acts as insulators.     

Enantioselective synthesis of tryptophan derivatives by a tandem Friedel-Crafts conjugate addition/asymmetric protonation reaction

The tandem Friedel-Crafts conjugate addition/asymmetric protonation reaction between 2-substituted indoles and methyl 2-acetamidoacrylate is reported. The reaction is catalyzed by (R)-3,3'-dibromo-BINOL in the presence of stoichiometric SnCl(4), and is the first example of a tandem conjugate addition/asymmetric protonation reaction using a BINOL·SnCl(4) complex as the catalyst. A range of indoles furnished synthetic tryptophan derivatives in good yields and high levels of enantioselectivity, even on a preparative scale. The convergent nature of this transformation should lend itself to the preparation of unnatural tryptophan derivatives for use in a broad array of synthetic and biological applications.     

Three anilides of 2,2′‐thiodibenzoic acid

The structures of N,N′‐bis(2‐methylphenyl)‐2,2′‐thiodibenzamide, C₂₈H₂₄N₂O₂S, (Ia), N,N′‐bis(2‐ethylphenyl)‐2,2′‐thiodibenzamide, C₃₀H₂₈N₂O₂S, (Ib), and N,N′‐bis(2‐bromophenyl)‐2,2′‐thiodibenzamide, C₂₆H₁₈Br₂N₂O₂S, (Ic), are compared with each other. For the 19 atoms of the consistent thiodibenzamide core, the r.m.s. deviations of the molecules in pairs are 0.29, 0.90 and 0.80 Å for (Ia)/(Ib), (Ia)/(Ic) and (Ib)/(Ic), respectively. The conformations of the central parts of molecules (Ia) and (Ib) are similar due to an intramolecular N—H...O hydrogen‐bonding interaction. The molecules of (Ia) are further linked into infinite chains along the c axis by intermolecular N—H...O interactions, whereas the molecules of (Ib) are linked into chains along b by an intermolecular N—H...π contact. The conformation of (Ic) is quite different from those of (Ia) and (Ib), since there is no intramolecular N—H...O hydrogen bond, but instead there is a possible intramolecular N—H...Br hydrogen bond. The molecules are linked into chains along c by intermolecular N—H...O hydrogen bonds.     

Diastereoselective synthesis of atropisomers containing two non-biaryl stereogenic axes: stereochemical relay through stereogenic centres in dihydrostilbene-2,2'-dicarboxamides

Addition of laterally lithiated tertiary aromatic amides to benzaldimines controls the formation of a new stereogenic centre adjacent to the benzaldimine aromatic ring. Drawing on the fact that such amino-substituted stereogenic centres may themselves control the conformation of amides, with amido-substituted benzaldimines we found it becomes possible to relay stereochemistry from one amide to another via this intervening stereogenic centre. A group of dihydrostilbene-2,2'-dicarboxamide derivatives bearing one or two stereogenic axes are made by this method, which demonstrates the use of combined kinetic and thermodynamic control for the relay of stereochemical information.     

Conformational studies of tertiary oligo-m-benzanilides and oligo-p-benzanilides in solution

A series of oligo-m- and p-benzanilides were made and their conformations in solution were studied by NMR. In most cases, conformational mixtures were observed as soon as three or more monomers were incorporated into the oligomer. Some crystal structures were obtained, which indicated that helical conformations were adopted in the solid state.