Stereocontrolled synthesis of trisubstituted cyclopropanes: expedient, atom-economical, asymmetric syntheses of (+)-Bicifadine and DOV21947

[reaction: see text] An expedient, atom-economical, asymmetric synthesis of 1-aryl-3-azabicyclo[3.1.0]hexanes, including (+)-Bicifadine and DOV21947, in a single-stage through process without isolation of any intermediates has been developed. The key of this synthesis is the in-depth mechanistic understanding of the complicated epoxy nitrile coupling at each reaction stage. Therefore, the desired trisubstituted cyclopropane can be prepared in high ee and yield by controlling the reaction pathway through manipulating the nitrile anion aggregation state.     

Dispersive Blow-Up Ⅱ.Schr(o)dinger-Type Equations,Optical and Oceanic Rogue Waves

Addressed here is the occurrence of point singularities which owe to the fo-cusing of short or long waves,a phenomenon labeled dispersive blow-up.The context of this investigation is linear and nonlinear,strongly dispersive equations or systems of equa-tions.The present essay deals with linear and nonlinear Schr(o)dinger equations,a class of fractional order SchrSdinger equations and the linearized water wave equations,with and without surface tension. Commentary about how the results may bear upon the formation of rogue waves in fluid and optical environments is also included.     

Search for singlet-triplet bistability or biradicaloid properties in polycyclic conjugated hydrocarbons: a valence-bond analysis

Two classes of molecules displaying singlet-triplet biradical bistability (i.e. species having significant biradicaloid properties) can be designed as follows. Alternant conjugated polycyclic hydrocarbons with numerous fixed double bonds (double bonds that remain unchanged in all its Kekulé resonance structures), a large number of Dewar resonance structures which measures the corresponding diradical resonance, and a small HOMO-LUMO band gap which measures the ease of thermal spin inversion are candidates for singlet triplet biradical bistability. Chichibabin's hydrocarbon ( 1 ) is an example. In addition, in the search for candidate molecules having singlet triplet bistability, one should also examine polycyclic conjugated systems having nonalternant induced spin frustration. Spin frustrated nonalternant polycyclic conjugated hydrocarbons will display singlet-triplet bistability (biradicaloid properties) and are generated from alternant valence-bond diradicals or Hückel molecular orbital diradicals having classical Kekulé structures by appropriate intramolecular joining of two starred or nonstarred positions with bonds, respectively.     

Temperature dependence of the dual phosphorescence from xanthone in n-hexane matrices

The phosphoresence spectrum and lifetime of xanthone embedded in an n-hexane matrix has been investigated as a function of temperature (1·6-100 K). Vibrational analyses of the spectra reveal that emission occurs from three sites, two of which are dominant. Emission from one site (B) occurs from the ³ nπ* state of a planar xanthone molecule and is characterized by strong totally symmetric carbonyl stretching vibrations and a short lifetime (2·4 ms). Emission from the other site (C) is shown to arise from the ³ππ* state of an out-of-plane distorted xanthone molecule. It displays a vibrational structure rich in modes of a ₁, b ₁, and b ₂ (C _2v notation) symmetry and a long lifetime (115 ms). Both direct spin orbit coupling via configurational mixing of the nπ* and ππ* states due to the non-planarity of the molecule in its ³ππ* state and spin-orbit vibronic interaction involving ³ A ₁(ππ*)-¹ A ₂(nπ*) spin-orbit and ¹ A ₂(nπ*)-¹ B ₂(ππ*) vibronic interaction via out-of-plane b ₁ vibrations are shown to be responsible for the C site emission intensity. Vibronic mixing between the ³ππ* and ³ nπ* states is not important. With increasing temperature, the phosphorescence intensity from the B site (³ nπ*) emitters increases at first, reaches a maximum at ～20 K and then decreases. The C site (³ππ*) intensity simply decreases with rising temperature. At a given temperature, the phosphorescence lifetimes are identical and exponential for all emission bands regardless of site origin. These observations indicate an equilibrium between emitters in the two sites throughout the lattice. A phonon-assisted energy transfer mechanism is proposed to account for these observations.     

Europium Oxychloride Absorption Spectroscopy as an Optical Probe of Temperature

The temperature dependence of the features which arise from the ⁷F_0,1 → ⁵D₃ absorption transitions in EuOCl as seen by diffuse-reflectance spectroscopy has been investigated. The transitions shift linearly to higher energy with increasing temperature. The ratio of the intensities of the transitions arising from the ⁷F₀ state to those arising from the ⁷F₁ state also appears to be a linear function of temperature.     

Anticancer Photodynamic Therapy Properties of Sulfur‐Doped Graphene Quantum Dot and Methylene Blue Preparations in MCF‐7 Breast Cancer Cell Culture

Photodynamic therapy (PDT) is a field with many applications including chemotherapy. Graphene quantum dots (GQDs) exhibit a variety of unique properties and can be used in PDT to generate singlet oxygen that destroys pathogenic bacteria and cancer cells. The PDT agent, methylene blue (MB), like GQDs, has been successfully exploited to destroy bacteria and cancer cells by increasing reactive oxygen species generation. Recently, combinations of GQDs and MB have been shown to destroy pathogenic bacteria via increased singlet oxygen generation. Here, we performed a spectrophotometric assay to detect and measure the uptake of GQDs, MB and several GQD‐MB combinations in MCF‐7 breast cancer cells. Then, we used a cell counting method to evaluate the cytotoxicity of GQDs, MB and a 1:1 GQD:MB preparation. Singlet oxygen generation in cells was then detected and measured using singlet oxygen sensor green. The dye, H₂DCFDA, was used to measure reactive oxygen species production. We found that GQD and MB uptake into MCF‐7 cells occurred, but that MB, followed by 1:1 GQD:MB, caused superior cytotoxicity and singlet oxygen and reactive oxygen species generation. Our results suggest that methylene blue's effect against MCF‐7 cells is not potentiated by GQDs, either in light or dark conditions.     

The development of improved syntheses of PPARγ-sparing,insulin sensitizing thiazolidinedione-ketones

Ketones 2 (MSDC-0160) and 3 (MSDC-0602) had been selected for clinical development, however their initial syntheses were considered suboptimal for application deep into clinical trials. Difficulties ranging from the nature of the starting material, alcohol oxidation problems, epoxide opening regioisomeric issues, and endgame ketone redox problems had been encountered. Direct ketone introduction/maintenance was desired for maximum efficiency and convergence was found to be critically dependent upon the acidity of the nucleophilic species (13, 18) and the use of pre- or post-alkylative oximino-ether/oxime protection (vide infra). Improvements in overall yield for the syntheses of 2 (MSDC-0160) and 3 (MSDC-0602) from 20% (2) and 31% (3) respectively, to 44% (2) and 59% (3) were realized.     

Template‐Free Synthesis of Highly b‐Oriented MFI‐Type Zeolite Thin Films by Seeded Secondary Growth

Highly b‐oriented, closely packed, MFI zeolite films are prepared on seeded stainless‐steel plates using organic template‐free, secondary growth solutions, containing aluminum sulfate as a crystallization agent. The number of a‐oriented twin crystals is significantly reduced, and even eliminated, simply by restricting the pH value of the secondary growth solution to the narrow range of 11.1–11.3. Values of pH can be adjusted through the controlled addition of (NH₄)₂SO₄ or H₂SO₄ to secondary growth solutions of the composition (1 SiO₂:0.57 NaOH:137.5 H₂O:0.0050 (Al₂(SO₄)₃?18 H₂O)) or by simply decreasing the molar composition of NaOH with no extra additives.