Formal meta-specific intramolecular Friedel–Crafts allylic alkylation of phenols through a spirocyclization–dienone–phenol rearrangement cascade

Formal meta-specific intramolecular Friedel–Crafts allylic alkylation of phenols was achieved based on spirocyclization–dienone–phenol rearrangement cascades. Systematic screening of acid catalysts revealed that Sc(OTf)₃ was a highly effective catalyst for dienone–phenol rearrangement of spiro[4.5]cyclohexadienones. Using 5 mol % of Sc(OTf)₃ as the promoter, various spirocyclic substrates were transformed into the corresponding phenol derivatives in good to excellent yield. Furthermore, the one-pot sequential spirocyclization–dienone–phenol rearrangement proceeded using a palladium and scandium multi-catalytic system or a triphenylmethyl cation single-catalyst system, providing the corresponding meta-allylated phenol derivatives in excellent yield.     

Synthesis of Dibenzocyclooctadienes by Anodic Oxidation

the use of electrochemical oxidation was applied to the synthesis of dibenzocyclooctadiene lactones related to steganacin skeleton. This reaction, performed with compounds 1 and 2, led to results comparable with the oxidation with RuTFA, TTFA and VOF₃.     

A Convenient Method for the Preparation of 4(e)-Hydroxy-and 4(e)-Methoxyadamantan-2-ones

Hydrolysis or methanolysis of 4(a)-(trifluoromethyl-sulfonyloxy)adamantan-2-one affords 4(e)-hydroxy-or 4(e)-methoxyadamantan-2-one, respectively, as major product, both of which are easily separated from minor by-products.     

Superhigh-Rate Epitaxial Silicon Thick Film Deposition from Trichlorosilane by Mesoplasma Chemical Vapor Deposition

Homoepitaxial Si thick films have been deposited by mesoplasma chemical vapor deposition (CVD) with SiHCl₃ (TCS)–H₂–Ar gas mixtures. The addition of a small amount of H₂ has been found to not only modify the film structure from polycrystalline to epitaxial but also effectively improve the deposition efficiency and film purity by removing Cl in the form of HCl. However, an excess introduction of H₂ decreases the deposition efficiency owing to the shrinkage of the plasma flame. On the other hand, an increase in TCS flow rate increases the epitaxial deposition rate despite exhibiting a saturating tendency, while the material yield tends to decrease gradually due possibly to an increase in the Cl atoms. Also, we observed a critical limit in the TCS flow rate for epitaxial growth, beyond which a polycrystalline film resulted. However, when RF input power was increased, not only the upper limit of TCS flow rate for epitaxy was extended but also the deposition yield was improved so that the deposition rate reached ~700 nm/s with the material yield of >50 % at 30 kW input power with an H₂/TCS ratio of 1.5. Additionally, high input power is found to be beneficial to decrease Cl atom incorporation into the film and improve the Hall mobility of the films. An epitaxial film with a Cl atom concentration of less than 3 × 10¹⁶ cm^?3 and a Hall mobility as high as 250 cm²/(V·s) was obtained at 30 kW input power.     

Giant vesicles prepared by nitroxide-mediated photo-controlled/living radical polymerization-induced self-assembly

Giant vesicles with several-micrometer diameters were prepared by self-assembly induced by the nitroxide-mediated photo-controlled/living radical polymerization. The random block copolymerization of methyl methacrylate (MMA) and methacrylic acid (MAA) were performed using poly(methacrylic acid) (PMAA) as the prepolymer in an aqueous methanol solution to produce a PMAA-block-poly(MMA-random-MAA) random block copolymer (PMAA-b-P(MMA-r-MAA)). PMAA₁₉₅-b-P(MMA_0.817-r-MAA_0.183)₂₂₄ formed spherical vesicles with a 4.74 μm diameter and 0.108 μm wall thickness. A differential scanning calorimetry analysis demonstrated that the vesicles had a bilayer structure consisting of a hydrophilic PMAA surface and hydrophobic P(MMA-r-MAA) interface. The wet vesicles before air-drying were flexible and easily transformed by stress, whereas the dry vesicles were fragile and cracked. The vesicles in the solution were dissociated into much smaller vesicles by increasing the temperature. They were also transformed by a further temperature increase into hollow fibers and finally into membranes retaining the bilayer structure.     

Synthesis, structure, and conformational mobility of a vaulted trans-bis(o-aminophenolato)platinum(II) complex

The synthesis, structure, and conformational mobility of a trans-bis(aminophenolato)platinum(II) complex bearing a dodecamethylene bridge, [Pt(L)] (1) [H ₂ L = N,N′-Dimethyl-N,N′-bis(2-hydroxyphenylmethyl)dodecane-1,12-diamine] are described. The 2D NMR and X-ray diffraction analysis revealed that the complex has a “reversed U”-shaped syn conformation in the solution state, which is mainly due to steric congestion of the vaulted structure and hydrogen bonding at the bis[(o-aminomethyl)phenolato] coordination site, while the complex unit is packed in the crystalline state with “Z-shaped” anti-conformation due to highly regulated molecular arrangement by 3D CH-π and hydrogen bonding interactions.     

Synthetic Studies on Sialoglycoconjugates 81: Synthesis of Positional Isomers of Sialyl Lewis X Epitope Containing 1-Deoxy-d Glucose in Place of N-Acetylglucosamine,and Their Inhibitory Activity to Selectin-Mediated Adhesion

Abstract

Three sialyl-Le^x epitope analogs, which carry fucose and α-sialyl-(2→3)-galactose residues at O-2 and O-3, O-3 and O-2, and O-4 and O-6 positions of 1-deoxy-D-glucose backbone, respectively, have been synthesized. Glycosylation of 1,5-anhydro-4,6-O-benzylidene-D-glucitol (1) or 1,5-anhydro-6-O-benzoyl-2,3-di-O-benzyl-d-glucitol (4) prepared from 1,5-anhydro-d-glucitol, with methyl 2,3,4-tri-O-benzyl-1-thio-β-L-fucopyranoside (5) using dimethyl(methylthio)sulfonium triflate (DMTST) as a promoter, afforded the corresponding fucosyl 1,5-anhydro-d-glucitol derivatives 7, 8 and 9. Glycosylation of 7, 8 or 10 derived from 9, with methyl O-(methyl 5-acetamido-4,7,8,9-tetra-O-acetyl-3,5-dideoxy-d-glyceroα-d-galacto-2-nonulopyranosylonate)-(2→3)-2,4,6-tri-O-benzoyl-1-thio-β-d-galactopyranoside (11) in the presence of DMTST gave the expected tetrasaccharide derivatives 12, 16 and 20. Hydrolysis of the benzylidene group in 12 and 16 gave compounds 13 and 17. Finally 13, 17 and 20 were transformed, by reductive removal of the benzyl groups, O-deacylation and subsequent hydrolysis of the methyl ester, into the sialyl-Le^x epitope analogs 15, 19 and 22, respectively.     

Carbon dioxide as a porogen on self-organized nano-structure of amphiphilic side-chain type liquid crystalline di-block copolymers

Liquid and supercritical carbon dioxide (LCO₂, SCCO₂) have been used as a porogen to swell self-organized nano-structure of an amphiphilic side-chain type liquid crystalline PEO–b-PMA(Az) copolymer. Carbon dioxide interacts with the hydrophilic PEO domain rather than the PMA matrix. The preferential interactions of PEO component with carbon dioxide result in a solvent-induced surface topology changes and the generation of a nano-porous template. The area density of the nano-pores is identical to that of the original copolymer film while keeping the hexagonally packed PEO nano-scale organization. Since the process is based on the gases diffusion on solid surfaces under controlled temperature and since neither polymer block is fundamentally altered by the sorption effect, the process is fully reversible. The supercritical condition of CO₂ treatment gives rise to the highest expansion of pre-patterned PEO cylinders and consecutively induces the retardation of PEO crystallization. This versatile thermo-diffuso approach would be applied to a wide variety of pre-patterned copolymers systems for nano-templating applications requiring nano-scale features sizes and/or area feature densities.     

Morphology transformation of micrometre-sized giant vesicles based on physical conditions for photopolymerisation-induced self-assembly

The physical conditions to vary the morphology of vesicles formed by amphiphilic poly(methacrylic acid)-block-poly(methyl methacrylate-random-methacrylic acid) were determined for the self-assembly induced by the nitroxide-mediated photocontrolled/living radical polymerisation performed in an aqueous methanol solution. The copolymer produced micrometre-sized spherical vesicles in the solution with a 30 wt% water content. The vesicles were transformed into a film-like morphology by decreasing the water content, whereas they were changed into nanometre-sized spherical vesicles by increasing it. The concentration of the growing polymer chain also varied the morphology. Large spherical vesicles formed at a low concentration were transformed into much smaller vesicles, followed by rod-like vesicles as a result of increasing the concentration. Furthermore, the stirring speed during the polymerisation-induced self-assembly dominated the morphology. Large elliptical vesicles produced at a low stirring speed changed into spherical vesicles, but decreased the size as the speed increased.     

Structure and Molecular Recognition of Chiral Amino-Cyclodextrin: One-dimensional Array by Self-assembly in Solid and Chiral Discrimination in Solution

Abstract

The crystal structure and molecular recognition behaviour of a new chiral-amino cyclodextrin are reported; van der Waals interaction, hydrogen bond and the electrostatic interactions play an important role in the self-assembling process and chiral recognition for (R)-(-)-and (S)-(+)-mandelic acid.