Dramatic Improvement in Catalyst Loadings and Molar Ratios of Coupling Partners for Ni/Cr-Mediated Coupling Reactions: Heterobimetallic Catalysts

Dramatic Improvement in Catalyst Loadings and Molar Ratios of Coupling Partners for Ni/Cr-Mediated Coupling Reactions: Heterobimetallic Catalyst

Dramatic Improvement in Catalyst Loadings and Molar Ratios of Coupling Partners for Ni/Cr-Mediated Coupling Reactions: Heterobimetallic Catalysts

Dramatic Improvement in Catalyst Loadings and Molar Ratios of Coupling Partners for Ni/Cr-Mediated Coupling Reactions: Heterobimetallic Catalyst

Molecular Design for Preparation of Hexagonal-Ordered Porous Films Based on Side-Chain-Type Liquid-Crystalline Star Polymer

Fabrication of regularly porous films by the breath-figure method has attracted much attention. The simple, low-cost technique uses the condensation of water droplets to produce these structures, but the phenomenon itself is complex, requiring control over many interacting parameters that change throughout the process. Developing a unified understanding for the molecular design of polymers to prepare ordered porous films is challenging, but required for further advancements. In this article, the effects of the chemical structure of polymers in the breath-figure technique were systematically explored using side-chain-type liquid-crystalline star polymers. The formation of porous films was affected by the structure of the polymers. Although the entire film surface of poly­(11-[4-(4-cyanobiphenyl)­oxy]­undecyl methacrylate) (<b>P11CB</b>) had a hexagonal ordered porous structure over a certain <i>M</i>_n value, regularly arranged holes did not easily form in poly­(methyl methacrylate) (<b>PMMA</b>), even though the main chain of <b>PMMA</b> is similar to that of <b>P11CB</b>. A comparison of <b>P11CB</b> and poly­(11-[(1,1′-biphenyl)-4-yloxy]­undecyl methacrylate) (<b>P11B</b>) (<b>P11CB</b> without cyano groups) showed that the local polar groups in hydrophobic polymers promoted the formation of ordered porous films. No holes were formed in poly­(4-cyanobiphenyl methacrylate) (<b>P0CB</b>) (<b>P11CB</b> without alkyl spacers) films due to its hydrophilicity. The introduction of alkyl chains in <b>P0CB</b> allowed the preparation of honeycomb-structured films by increasing the internal tension. However, alkyl chains in the side chain alone did not result in a porous structure, as in the case of poly­(undecyl methacrylate) (<b>P11</b>). Aromatic rings are also required to increase the <i>T</i>_g and improve film formability. In the present study, suitable molecular designs of polymers were found, specifically hydrophobic polymers with local polar groups, to form a regularly porous structure. Development of clear guidelines for the molecular design of polymers is the subject of our current research, which will enable the fabrication of porous films using various functional polymers

Synthesis of the Bicyclo[7.3.0]dodecatrienediyne Core of the C-1027 Chromophore

C-1027, an extremely potent antitumor agent, is composed of chromophore 1 and an apoprotein. Here we report a general and efficient route to the exceedingly reactive bicyclo[7.3.0]dodecatrienediyne core of 1, utilizing selenoxide elimination and epoxide deoxygenation to build the cyclopentadiene and enediyne structures, respectively

Dismantlable Thermosetting Adhesives Composed of a Cross-Linkable Poly(olefin sulfone) with a Photobase Generator

A novel photodetachable adhesive was prepared using a photodepolymerizable cross-linked poly­(olefin sulfone). A mixture of a cross-linkable poly­(olefin sulfone), a cross-linking reagent, and a photobase generator functioned as a thermosetting adhesive and exhibited high adhesive strength on quartz plates comparable to that obtained for commercially available epoxy adhesives. The cured resin was stable in the absence of UV light irradiation but completely lost its adhesive strength upon exposure of glued quartz plates to UV light in conjunction with heating to 100 °C

Toolbox Approach to the Search for Effective Ligands for Catalytic Asymmetric Cr-Mediated Coupling Reactions

Chromium catalysts derived from chiral sulfonamides represented by A effect the couplings of aldehydes with vinyl, allyl, or alkyl halides. With three distinct sites for structural modification, A affords access to a structurally diverse pool of chiral sulfonamides. The Cr catalysts derived from these sulfonamides exhibit a broad range of catalyst−substrate matching profiles. A strategy is presented to search for a satisfactory chiral sulfonamide for a given substrate. In order to demonstrate the generality and effectiveness of this approach, five diverse C−C bond-forming cases have been selected from the halichondrin synthesis. For each of the cases, two ligands have been deliberately searched for, to induce the formation of (R)- and (S)-alcohols, respectively, at the arbitrarily chosen efficiency level of “≥80% yield with ≥20:1 stereoselectivity in the presence of ≤20 mol % of a Cr catalyst”. For 9 out of the 10 cases studied, a satisfactory catalyst has been found within this pool of sulfonamides. Even for the remaining case, a Cr catalyst inducing stereoselectivity up to 8:1 has been identified

New Syntheses of E7389 C14−C35 and Halichondrin C14−C38 Building Blocks: Reductive Cyclization and Oxy-Michael Cyclization Approaches

Cr-mediated coupling reactions are usually achieved with a slight excess of a given nucleophile. To develop a cost-effective use of this process, two different approaches have been studied. The first approach depends on two consecutive catalytic asymmetric Cr-mediated couplings, with use of coupling partners purposely being of unbalanced molecular size and complexity. The second approach rests on the success in identifying the nucleophile, which allows us to achieve the coupling satisfactorily with a 1:1 molar ratio of the coupling partners. The C23−O bond is stereospecifically constructed via reductive cyclization of the oxonium ion, or oxy-Michael cyclization. Both syntheses have a high overall efficiency: E7389 C14−C35 and halichondrin C14−C38 building blocks have been synthesized from the corresponding C27−C35 and C27−C38 aldehydes, respectively, in high overall yields with an excellent stereoselectivity. Because of operational simplicity, the synthesis outlined herein appears to be well suited for scaling

Updatable Holographic Diffraction of Monolithic Carbazole-Azobenzene Compound in Poly(methyl methacrylate) Matrix

The comprehensive mechanism of updatable holographic diffraction is presented for a monolithic compound of 3-[(4-nitrophenyl)­azo]-9H-carbazole-9-ethanol (NACzE) dispersed poly­(methyl methacrylate) film device. The maximum sensitivity occurs at 561 nm, which well coincides with an isosbestic point between <i>cis</i>-<i>trans</i> isomers of NACzE molecule. The holographic grating is ascribed to the absorption grating and the following refractive index grating due to the photo-orientation of NACzE molecules. The response and decay times for the diffraction are governed by the glass transition temperature of the matrix

Ten-Gram-Scale Total Synthesis of the Anticancer Drug Candidate E7130 to Supply Clinical Trials

E7130 is a novel drug candidate with an exceedingly complex chemical structure of the halichondrin class, discovered by a total synthesis approach through joint research between the Kishi group at Harvard University and Eisai. Only 18 months after completion of the initial milligram-scale synthesis, ten-gram-scale synthesis of E7130 was achieved, providing the first good manufacturing practice (GMP) batch to supply clinical trials. This paper highlights the challenges in developing ten-gram-scale synthesis from the milligram-scale synthesis