A new way to make a bang : Several functionalized 1‐ethyl‐5‐aminotetrazoles, 1‐ethyl‐5‐nitrimino‐tetrazoles, and copper complexes have been synthesized and their chemical and energetic properties have been comprehensively characterized. The compounds belong to all classes of “energetic materials”: explosives, propellants, and pyrotechnics.
What a difference ! The energy differences between anti and syn conformers as well as the energy barrier for the rotation around the aryl–aryl bond of a number of 2,2′‐bipyridine molecules were examined by quantum‐chemical methods. The energy differences were found to be governed by the substituents directly attached to the bipyridine and their ability to form intramolecular hydrogen bonds.
Cage me! A linear dumbbell‐shaped bipyridinium molecule can template cage formation around itself through sixfold imine bond formation to give an interlocked [2]rotaxane as the single product (see picture). This highly efficient [2+3] clipping occurs despite the symmetry mismatch between the template and the formed macrobicycle.
Two members of a family of pyrrole–imidazole marine alkaloids, (+)‐dibromophakellin and the nonnatural congener (+)‐phakellin, were synthesized enantioselectively from 4‐hydroxy‐L ‐proline. The chiral aminal at C10 was constructed efficiently by means of an Overman‐type [3,3] sigmatropic rearrangement of an enamide (see scheme).
A catalytic route toward chiral Morita–Baylis–Hillman esters by asymmetric coupling between α,β‐acetylenic esters, aldehydes, and trimethylsilyl iodide has been developed (see scheme). The reaction proceeds with high to excellent enantioselectivities, and the products can be transformed into β‐branched derivatives in a single step and with excellent retention of configuration. TMS=trimethylsilyl
You can append on me! Porphyrin‐appended polynorbornenes derived from 5,6‐endo‐fused N‐arylpyrrolidenonorbornenes have been shown to have coherently aligned pendant groups that exhibit exciton coupling and fluorescence quenching in the absorption and emission profiles (see figure).
Bromide is best : The first [2]rotaxane incorporating the triazolium anion‐binding motif is prepared using bromide anion templation. Preliminary anion‐binding investigations reveal that the rotaxane exhibits the rare selectivity preference for bromide over chloride ions.
Trapped in a “tea bag” : Membrane bags, fabricated from a dialysis membrane, have been employed as semipermeable containers for dendrimer‐immobilised oxazoline–copper(II) Lewis acid catalysts. Dipping them into reactant solutions leads to the catalytic conversion of the substrates, which penetrate the membrane as does the product in the reverse direction (see scheme).
Minimum requirements : Crystals and thin films of 1,4‐bis(alkenyl)‐2,5‐dipiperidinobenzenes, which contain only one benzene ring as the aromatic component, emit visible light with excellent solid‐state quantum yields upon irradiation with UV light. Polystyrene thin films doped with the benzenes also exhibit brilliant fluorescence. By modifying the alkenyl groups, the emission color can be tuned in the range from blue to red.
