Asymmetric Desymmetrization via Metal‐Free C−F Bond Activation: Synthesis of 3,5‐Diaryl‐5‐fluoromethyloxazolidin‐2‐ones with Quaternary Carbon Centers

We disclose the first asymmetric activation of a non‐activated aliphatic C?F bond in which a conceptually new desymmetrization of 1,3‐difluorides by silicon‐induced selective C?F bond scission is a key step. The combination of a cinchona alkaloid based chiral ammonium bifluoride catalyst and N,O‐bis(trimethylsilyl)acetoamide (BSA) as the silicon reagent enabled the efficient catalytic cycle of asymmetric C_sp3?F bond cleavage under mild conditions with high enantioselectivities. The ortho effect of the aryl group at the prostereogenic center is remarkable. This concept was applied for the asymmetric synthesis of promising agrochemical compounds, 3,5‐diaryl‐5‐fluoromethyloxazolidin‐2‐ones bearing a quaternary carbon center.     

Use of the Wilson equation to calculate solid-liquid phase equilibria in binary and ternary systems

Generalized formulation is presented for calculating simple eutectic type solid-liquid phase diagrams for binary and ternary systems by using the Wilson equation for molar excess Gibbs energy in the liquid phase. The liquidus surface and eutectic points of molten salt mixtures with a common ion were calculated and compared with experimental values. The average error in the estimation of ternary eutectic composition was ± 0.013 (mole fraction) for the two ternary systems tested. The agreement was generally better than that obtained with the regular solution approximation.     

Frame-rate analysis of arterial blood flow in human and rat using laser speckle image sensing

In imaging of blood flow by means of a laser speckle technique, we have proposed so far an estimation parameter based on the spatial contrast of speckle patterns observed for the blood flow in skin tissue and a blood vessel. This parameter enable us to image a relative blood flow distribution from a single speckle pattern, thus, it analyzes the blood flow with a frame-rate of an imaging device used. In this study, we investigated availability of this parameter for detecting changes in arterial blood flow caused by medication and cold stimulation to the skin tissue. Experiments were conducted for an anesthetized rat and a human wrist to confirm the feasibility of the present parameter.     

Synthesis and Reactivity of Cyclic Borane‐Amidine Conjugated Molecules Formed by Direct 1,2‐Carboboration of Carbodiimides with 9‐Borafluorenes

Efficient 1,2‐carboboration reactions to the C=N bond of carbodiimides with 9‐borafluorenes, which give rise to cyclic borane‐amidine conjugates with a seven‐membered BNC₅ ring, are reported. The resulting cyclic borane‐amidine conjugates can be hydrolyzed into an acyclic bifunctional biaryl compound carrying both boronic acid and amidine groups, rendering the utility of the two‐step protocol for the synthesis of multi‐functionalized molecular systems with a potential as a supramolecular building block. Furthermore, the conjugated structure of the cyclic boron‐amidine compounds can be changed upon alkylation of the boron atom that increases the coordination number of boron. The combination of Lewis acid (borane) and conjugated base (amidine) provides rich structural diversity of heteroatom‐containing π‐conjugated systems.     

Water‐soluble complex formation of fullerene and thermo‐responsive diblock copolymer

A diblock copolymer (P₉₈N₁₀₀) composed of a biocompatible water‐soluble block (PMPC) and a lower critical solution temperature (LCST) type thermo‐responsive block (PNIPAM) was prepared via controlled radical polymerization. To dissolve fullerene (C₆₀) in water, the C₆₀/P₉₈N₁₀₀ complex was prepared by mixing C₆₀ and P₉₈N₁₀₀ powders. The maximum solubilized C₆₀ concentration in water was 1.39 g/L, as estimated from UV–vis adsorption, when the polymer concentration was 5.0 g/L. The percent transmittance of the aqueous solution of the C₆₀/P₉₈N₁₀₀ complex decreased above 36 °C due to inter‐complex association above the LCST for the PNIPAM block. While the hydrodynamic radius of C₆₀/P₉₈N₁₀₀ complex was 135 nm at 20 °C, it increased to 161 nm at 50 °C. Despite the observation of ¹H NMR signals from PMPC and PNIPAM blocks for the C₆₀/P₉₈N₁₀₀ complex in D₂O at room temperature, the signals from PNIPAM disappeared above 35 °C due to restricted motion of PNIPAM. Generation of singlet oxygen (¹O₂) from the C₆₀/P₉₈N₁₀₀ complex by photo‐irradiation was confirmed using 9,10‐anthracene dipropionic acid (ADPA). The absorbance of ADPA decreased with increasing irradiation time due to oxidation of ADPA by ¹O₂. It is expected that the C₆₀/P₉₈N₁₀₀ complex can be applied as a thermo‐responsive carrier for photodynamic therapy. © 2017 Wiley Periodicals, Inc. J. Polym. Sci., Part A: Polym. Chem. 2017 , 55, 2432–2439     

Aerobic oxidative desymmetrization of meso-diols with bifunctional amidoiridium catalysts bearing chiral N-sulfonyldiamine ligands

Asymmetric aerobic oxidation of a range of meso- and prochiral diols with chiral bifunctional Ir catalysts is described. A high level of chiral discrimination ability of Cp^∗Ir complexes derived from (S,S)-1,2-diphenylethylenediamine was successfully demonstrated by desymmetrization of secondary benzylic diols such as cis-indan-1,3-diol and cis-1,4-diphenylbutane-1,4-diol, providing the corresponding (R)-hydroxyl ketones with excellent chemo- and enantioselectivities. Enantiotopic group discrimination in oxidation of symmetrical primary 1,4- and 1,5-diols gave rise to chiral lactones with moderate ees under similar aerobic conditions.     

Total Synthesis of Indole and Dihydroindole Alkaloids. XV. Further Chemistry of Vindoline

The general reactivity of various sites in the vindoline series has been investigated. The facility of electrophilic substitution at C(15) and the effect of steric crowding on reactions at C(4) are discussed. At the basic nitrogen sites, oxidations with mercuric acetate and potassium permanganate are also discussed.     

Stereocontrolled synthesis of the C79-C96 fragment of symbiodinolide

The stereoselective synthesis of the C79-C96 fragment of symbiodinolide is described in which the spiroacetalization and Kotsuki coupling are the key steps.     

Synthesis of γ‐Boryl‐Substituted Homoallylic Alcohols with anti Stereochemistry Based on a Double‐Bond Transposition

The stereoselective synthesis of anti isomers of γ‐boryl‐substituted homoallylic alcohols is disclosed. (E)‐1,2‐Di(boryl)alk‐1‐enes undergo Ru‐catalyzed double‐bond transposition with control of the geometry. The in situ generated (E)‐1,2‐di(boryl)alk‐2‐enes add to aldehydes in a stereospecific manner. The alkenylboron group within the product is amenable to a variety of synthetic derivatizations.