Solid-state hosts by the template polymerization of columnar liquid crystals: locked supramolecular architectures around chiral 2-amino alcohols

The cross-linking of multicomponent liquid crystals could be applied to the synthesis of nanometer-sized porous materials with a well-defined structure. In this work we demonstrate the template polymerization of columnar liquid crystals composed of the salts of a carboxylic acid and enantiopure 2-amino alcohols, and the application of one of them as a solid-state host. The salts of 3,4,5-tris(11-acryloyloxyundecyloxy)benzoic acid with (S)-2-amino-1-propanol and with (1R,2S)-norephedrine showed hexagonal and rectangular columnar liquid-crystalline structures, respectively. The successful application of gamma-ray-induced polymerization to the cross-linking of the liquid-crystalline salts, which was more advantageous than photoinduced polymerization from the standpoint of the retention of the original structural order in the gram-scale preparation of the polymers with a homogeneous columnar structure. The cross-linked polymer thus obtained from the gallic acid derivative and (1R,2S)-norephedrine was applicable as a heterogeneous host to capture amines from a guest solution through acid-amine interactions. When (1R,2S)-norephedrine was replaced with other amines through the guest-exchange reaction, a "template effect" was observed; the size and shape of the guests were determining factors for the efficiency of the guest exchange. The guest adsorption was found to proceed in an enantioselective manner when racemic 2-amino alcohols were used as guests, especially in the cases of substrates possessing a bulky substituent at the C1-position. The guest preference was again elucidated by the template effect, although the enantioselection mode was switched depending on the presence of a C2 substituent.     

Self-organization of all-inorganic dodecatungstophosphate nanocrystallites

The crystallinity and porosity of all-inorganic dodecatungstophosphate M3PW12O40 (M=Cs, NH4, Ag, denoted as MPW) particles are controlled by the changes in the synthetic temperatures and countercations. The MPW particles can be classified into three groups by the crystallinity and porosity: (i) mesoporous "disordered" aggregates, (ii) microporous "self-organized" aggregates, and (iii) nonporous single crystals. The formation and growth mechanism of MPW particles is expressed by three steps: formation of nanocrystallites, assembly of the nanocrystallites to form aggregates, and the growth of aggregates by the attachment of nanocrystallites. The time courses of the turbidity of the synthetic solution, the concentration of the nanocrystallites, and the average particle sizes of MPW particles are well reproduced by the calculation based on the mechanism.     

Efficient conversion of tomatidine into neuritogenic pregnane derivative

Moderate acetylation of tomatidine with anhydrous acetic acid and pyridine for 20 h at r.t., followed by pseudomerization in ice-water, gave a delta(20(22))-pseudo compound, which was then subjected to ozonolysis to provide a pregnane derivative in a total 54% yield showing neuritogenic and NGF-enhancing activities.     

A molecular leverage for helicity control and helix inversion

The helical tetranuclear complex [LZn(3)La(OAc)(3)] having two benzocrown moieties was designed and synthesized as a novel molecular leverage for helicity control and helix inversion. Short alkanediammonium guests H(3)N(+)(CH(2))(n)NH(3)(+) (n = 4, 6, 8) preferentially stabilized the P-helical isomer of [LZn(3)La(OAc)(3)], while the longer guest H(3)N(+)(CH(2))(12)NH(3)(+) caused a helix inversion to give the M-helical isomer as the major isomer. The differences in the molecular lengths were efficiently translated into helical handedness via the novel molecular leverage mechanism using the gauche/anti conversion of the trans-1,2-disubstituted ethylenediamine unit.     

Platinum-catalyzed consecutive C-N bond formation-[1,3] shift of carbamoyl and ester groups

The reaction of ortho-alkynylphenylureas 1 having a carbamoyl group attached to the nitrogen atom proceeded in the presence of catalytic amounts of PtI₄, affording corresponding indole-3-carbamides 2 in moderate to high yields. In addition, the platinum-catalyzed cyclization of ortho-alkynylphenyl carbamates 3 afforded corresponding indole-3-carboxylates 4 in good yields. The present reaction proceeds through the intramolecular addition of carbon-nitrogen bonds to triple bonds, the so-called carboamination.     

Cyclization of aryl acyl radicals generated from S-(4-cyano)phenyl thiolesters by a nickel complex catalyzed electroreduction

Aromatic acyl radicals generated from S-(4-cyano)phenyl 2-alkenylthiobenzoate by a nickel complex catalyzed electroreduction undergo 5- and 6-exo cyclization to give 1-indanone and dihydro-1-naphthalenone derivatives, respectively.