Photocyclization reactions. Part 8. Synthesis of 2‐quinolone,quinoline and coumarin derivatives using trans‐cis isomerization by photoreaction

2‐Quinolone 2 , quinoline 3 , coumarin (2H‐1‐benzopyran‐ 2 ‐one) 5 , and 2H‐1‐benzopyran hemiacetal 6 were synthesized by photocyclization reaction of traans‐o‐aminocinnamoyl derivatives trans‐ 1 and trans‐o‐hydroxycinnamoyl derivatives trans‐ 4 . The reaction proceeds through trans‐cis isomerization followed by intramolecular cyclization.     

Enzyme-based microtiter plate assay for γ-aminobutyric acid: Application to the screening of γ-aminobutyric acid-producing lactic acid bacteria

An enzyme-based microtiter plate assay for γ-aminobutyric acid (GABA) was developed. GABA was quantified using γ-aminobutyrate glutamate aminotransferase and succinic semialdehyde dehydrogenase in the presence of NADP⁺ and -ketoglutarate. The NADPH produced by the series of enzymatic reactions was measured spectrophotometrically at 340 nm. A linear relationship between absorbance and the concentration of GABA was obtained in the ranges from 5.0 × 10⁻⁴ to 1.0 × 10⁻² M. The relative standard deviation for 10 successive measurements was 0.9% at the 10 mM GABA level. This analytical method was applied to the screening of GABA-producing lactic acid bacteria in de Man–Rogosa–Sharpe (MRS) medium. The proposed method enables one to assay 96 samples for an hour without the pre-treatment of samples. The method is by far superior to the traditional HPLC method from the point of view of rapidity and simplicity.     

Stereoselective CH Borylations of Cyclopropanes and Cyclobutanes with Silica‐Supported Monophosphane–Ir Catalysts

Heteroatom‐directed C?H borylation of cyclopropanes and cyclobutanes was achieved with silica‐supported monophosphane–Ir catalysts. Borylation occurred at the C?H bonds located γ to the directing N or O atoms with exceptional cis stereoselectivity relative to the directing groups. This protocol was applied to the borylation of a tertiary C?H bond of a ring‐fused cyclopropane.     

Sequence-regulated copolymers via tandem catalysis of living radical polymerization and in situ transesterification

Sequence regulation of monomers is undoubtedly a challenging issue as an ultimate goal in polymer science. To efficiently produce sequence-controlled copolymers, we herein developed the versatile tandem catalysis, which concurrently and/or sequentially involved ruthenium-catalyzed living radical polymerization and in situ transesterification of methacrylates (monomers: RMA) with metal alkoxides (catalysts) and alcohols (ROH). Typically, gradient copolymers were directly obtained from the synchronization of the two reactions: the instantaneous monomer composition in feed gradually changed via the transesterification of R(1)MA into R(2)MA in the presence of R(2)OH during living polymerization to give R(1)MA/R(2)MA gradient copolymers. The gradient sequence of monomers along a chain was catalytically controlled by the reaction conditions such as temperature, concentration and/or species of catalysts, alcohols, and monomers. The sequence regulation of multimonomer units was also successfully achieved in one-pot by monomer-selective transesterification in concurrent tandem catalysis and iterative tandem catalysis, providing random-gradient copolymers and gradient-block counterparts, respectively. In contrast, sequential tandem catalysis via the variable initiation of either polymerization or in situ transesterification led to random or block copolymers. Due to the versatile adaptability of common and commercially available reagents (monomers, alcohols, catalysts), this tandem catalysis is one of the most efficient, convenient, and powerful tools to design tailor-made sequence-regulated copolymers.     

Copolymerization of N-ethylmaleimide with stilbenes

Charge-transfer complexes in solutions of ethylmaleimide and stilbenes have been characterized by spectroscopy. The stoichiometric compositions of these complexes have been shown by Job's method to be 1:1 molar complexes. The value of the equilibrium constant K for complex formation of ethylmaleimide with stilbene derivative increases in the following probable order: ethylmaleimide–stilbene ? ethylmaleimide–dimethylaminostilbene (DMAS) < ethylmaleimide–aminodimethylaminostilbene (ADMAS). From the calculations of the electron density of the highest occupied level for the stilbenes, the charge transfer in ethylmaleimide–DMAS and ethylmaleimide–ADMAS is attributed to n → π transition, while the charge transfer in ethylmaleimide-stilbene is attributed to n → π transition. Copolymerization was carried out by γ-irradiation in benzene or THF solutions of the comonomer pairs. The alternating tendency of copolymerization was larger in the ethylmaleimide–DMAS system than in the ethylmaleimide–stilbene system. This can be explained by assuming resonance structures in the transition state of addition reaction of DMAS to the propagating ethylmaleimide unit. In the copolymerization of ethylmaleimide with ADMAS, the effect of the penultimate unit was more important than in that with DMAS.     

Preparation of axially chiral biphenyl diphosphine ligands and their application in asymmetric hydrogenation

Axially chiral biphenyldiphosphine ligands bearing diphenylphosphino group(s) and/or dicyclohexylphosphino group(s) were prepared in enantiomerically pure form starting from 2,6-dimethylnitrobenzene via 8 steps: iodination, reduction, methoxylation through diazotization, Ullmann coupling, bromination, phosphorylation, optical resolution, and silane reduction, and the obtained ligands were used in rhodium-catalyzed asymmetric hydrogenation.     

Threshold characteristics of microcavity semiconductor lasers

The influence of spontaneous emission coupling on the threshold characteristics of microcavity semiconductor lasers is studied using explicit algebraic expressions for the pump rate dependence of photon and carrier numbers. It is shown that fractional spontaneous emission coupling in practical microcavity laser structures imposes limitations on thresholdless lasing operation.     

Spontaneous breaking of scale invariance in a supersymmetric model

The phase structure of a large N, O(N) supersymmetric model in three dimensions is studied. Of special interest is the spontaneous breaking of scale invariance which occurs at a fixed value of the coupling constant, λ₀=λ_c=4π. In this phase the bosons and fermions acquire a mass while a Goldstone boson (dilaton) and Goldstone fermion (“dilatino”) are dynamically generated as massless bound states. The absence of renormalization of the dimensionless coupling constant λ₀ leaves these Goldstone particles massless.     

Optical characterization of photonic crystal delay lines based on one-dimensional coupled defects

We performed optical characterizations of optical delay lines based on photonic crystal waveguides. The delay lines were composed of cylindrical air holes in silicon-on-silicon-dioxide ridge waveguides, defects were periodically created by means of increasing the separation of two neighboring air holes, and the structure was designed to have flat-transmittance impurity band. We clearly observed an impurity band with a bandwidth of ~30 nm and a maximum transmittance of ~0.5 at an operating wavelength of ~1.55 microm . A 600-fs delay was confirmed with a 20-microm -long delay line. A good agreement was confirmed between the experimental results and the calculations.