All Non-Carbon B3NO2 Exotic Heterocycles: Synthesis,Dynamics, and Catalysis

The B₃NO₂ six-membered heterocycle (1,3-dioxa-5-aza-2,4,6-triborinane=DATB), comprising three different non-carbon period 2 elements, has been recently demonstrated to be a powerful catalyst for dehydrative condensation of carboxylic acids and amines. The tedious synthesis of DATB, however, has significantly diminished its utility as a catalyst, and thus the inherent chemical properties of the ring system have remained virtually unexplored. Here, a general and facile synthetic strategy that harnesses a pyrimidine-containing scaffold for the reliable installation of boron atoms is disclosed, giving rise to a series of Pym-DATBs from inexpensive materials in a modular fashion. The identification of a soluble Pym-DATB derivative allowed for the investigation of the dynamic nature of the B₃NO₂ ring system, revealing differential ring-closing and -opening behaviors depending on the medium. Readily accessible Pym-DATBs proved their utility as efficient catalysts for dehydrative amidation with broad substrate scope and functional-group tolerance, offering a general and practical catalytic alternative to reagent-driven amidation.     

Electroneutrality coupling of electron transfer at an electrode surface and ion transfer across the interface between thin-layer of 1-octyl-3-methylimidazolium bis(perfluoroalkylsulfonyl)imide covering the electrode surface and an outer electrolyte solution.

The electrode reaction of decamethylferrocene (DMFc) dissolved in a thin layer of a room-temperature molten salt (RTMS), 1-octyl-3-methylimidazolium bis(trifluoromethylsulfonyl)imide (C8mimC1C1N) or 1-octyl-3-methylimidazolium bis(pentafluoroethylsulfonyl)imide (C8mimC2C2N), on a self-assembled monolayer-modified gold electrode is coupled with the ion transfer across the interface between the RTMS and the outer aqueous solution (W) to give a voltammogram whose shape resembles a voltammogram of a simple one-electron transfer process. The electroneutrality of the RTMS layer during the oxidation of DMFc to decamethylferricenium ion is maintained by the concomitant dissolution of C8mim+ ion from the RTMS phase to the W phase, and the reduction of decamethylferricenium ion to DMFc is accompanied by the transfer of either C1C1N- or C2C2N- from RTMS to W. The midpoint potential of the voltammogram varies with the concentration of the salt in the aqueous phase, C8mimCl or LiCnCnN (n = 1 or 2), in a Nernstian manner, showing that the phase-boundary potential between the RTMS and the W is controlled by the partition of these ions. Although the phase-boundary potential across the RTMS / W interface is Nernstian with respect to the ions common to both phases at the equilibrium, the polarization at the RTMS / W interface under current flow distorts the shape of the voltammograms, resulting in a wider peak separation in the voltammogram.     

A -series identity and the arithmetic of Hurwitz zeta functions

Using a single variable theta identity, which is similar to the Jacobi Triple Product identity, we produce the generating functions for values of certain expressions of Hurwitz zeta functions at non-positive integers.     

Re-entrant phase transitions of the Blume-Emery-Griffiths model

We have investigated the spin-1 Ising model on the simple cubic lattice with bilinear, biquadratic interaction and anisotropic energy (BEG model). We have been specially interested in the case of antiferro biquadratic interaction, because the interaction will cause the competition with bilinear interaction and anisotropy. A two-sublattice ordering, so called the staggered quadrupole (SQ) phase, occurs as long as biquadratic interaction is negative large enough. We have obtained a full phase diagram in the whole interaction parameter space (for the positive bilinear interaction) by the Bethe approximation, and found several kinds of phase transitions, such as successive, re-entrant and double re-entrant transitions. These transitions are also confirmed by Monte Carlo simulations on simple cubic lattices.     

Synthesis and biological activities of analogs of a lipid A biosynthetic precursor: 1-O-phosphonooxyethyl-4'-O-phosphono-disaccharides with (R)-3-hydroxytetradecanoyl or tetradecanoyl groups at positions 2, 3, 2' and 3'.

Two novel analogs of a biosynthetic precursor of lipid A (2) were synthesized. The one analog (3) has acyl groups identical to those of 2, and the other (4) has tetradecanoyl groups in place of the (R)-3-hydroxytetradecanoyl groups of 2. Both 3 and 4 possess an alpha-glycosidically-bound phosphonooxyethyl group in place of the alpha-glycosyl phosphate group of 2. Compounds 3 and 4 exhibited definite antitumor activity against Meth A fibrosarcoma and low toxicity in rabbits, as the original compound 2 does. The replacement of the hydroxytetradecanoyl groups with tetradecanoyl groups barely affected the antitumor activity, but slightly enhanced the toxicity in rabbits.     

Synthesis of self‐photosensitizing polyesters containing donor–acceptor norbornadiene moieties and benzophenone groups and their photochemical reactions

The ring‐opening copolymerization of a glycidyl ester derivative having a benzophenone group and the donor–acceptor norbornadiene (D‐A NBD) dicarboxylic acid, 5‐(4‐methoxyphenyl)‐1,4,6,7,7‐pentamethyl‐2,5‐norbornadiene‐2,3‐dicarboxylic acid, monoglycidyl ester derivatives with D‐A NBD dicarboxylic anhydride using tetraphenylphosphonium bromide as a catalyst proceeded smoothly to give novel self‐photosensitizing NBD polymers in good yields. The molecular weight of these polyesters was about 4,000, and lower than that of analogous NBD polymers having no benzophenone group. All the synthesized NBD polymers isomerized smoothly to the corresponding quadricyclane (QC) polymers upon UV irradiation in tetrahydrofuran (THF) solution and in the film state. The rate of the photoisomerization of the D‐A NBD moieties in these polymers was higher than that of the D‐A NBD moieties in the polymer having no photosensitizing group. Furthermore, the rate of the photoisomerization of the D‐A NBD moieties in these polymers was also higher than that of the NBD polymer with low molecular weight photosensitizer in dilute solution. The photo‐irradiated polymers having QC moieties released thermal energies of 146–180 J/g. The D‐A NBD moieties contained in these NBD polymers possessed fair to good fatigue resistance. The degradation of the NBD moieties in these polymers was 15–30% after 50 repeated cycles of interconversion. © 2007 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem 45: 2978–2988, 2007