Noriyuki Yonezawa

Bio: Noriyuki Yonezawa is an academic researcher from Tokyo University of Agriculture and Technology. The author has contributed to research in topics: Electrophilic aromatic substitution & Ether. The author has an hindex of 19, co-authored 109 publications receiving 1038 citations. Previous affiliations of Noriyuki Yonezawa include University of Tokyo & Japan Atomic Energy Research Institute.

Reversible ArSE Aroylation of Naphthalene Derivatives

Abstract: Reversible ArS E aroylation has been observed in the reaction of 2,7-dimethoxynaphthalene (1) with 4-chlorobenzoic acid/acid chloride 2 with the aid of discrete acidic mediators. The reaction readily gives 1-aroylated-, 3-aroylated-, and 1,8-diaroylated products. The product distribution clearly shows dependence on the kind and strength of the acidic mediators and the time-course of the distribution manifests dearoylation of the productive aroylnaphthalenes. These reaction behaviors including acid-strength-dependent reversibility are well interpreted from the viewpoint of highly congested noncoplanar geometry of the polyaromatic ketone products.

Lewis Acid-mediated ArSE Aroylation of Naphthalene Derivative: Distinct Second Aroylation Behavior of α-Naphthyl Ketone

Abstract: Dual ArSE aroylation of 2,7-dimethoxynaphthalene proceeds with distinct susceptibility and regioselectivity depending on the Lewis acid The TiCl4-mediated reaction readily affords 1,8-diaroylated

Symmetric and asymmetric photocleavage of the cyclobutane rings in head-to-head coumarin dimers and their lactone-opened derivatives

Abstract: The photochemical behaviour of fifteen derivatives of head-to-head coumarin dimers has been investigated. The photocleavage of the cyclobutane rings in these compounds in solution occurs on irradiation with light of wavelength 277 ± 10 nm to give two molecules of coumarin derivatives via symmetric fission and/or 2,2′-dihydroxystilbene and fumaric (and maleic) acid derivatives via asymmetric fission. The direction of these photofissions is primarily affected by the basic structure of the coumarin dimer derivative, the photocleavage proceeding exclusively with retention of the ring structure when the derivative has a stable five- or six-membered ring fused to its cyclobutane ring. A secondary influence is the steric repulsion between the substituents attached to the cyclobutane ring.

Successful synthesis of wholly aromatic polyketones via nickel-mediated aromatic coupling polymerization

Abstract: Novel aromatic polyketones (8a, 8b) without ether linkage in the main chain were successfully synthesized via nickel-mediated aromatic coupling polymerization of bis(chlorobenzoyl)dimethoxybiphenyls (3a, 3b). The polymers affording flexible films were obtained in the reaction where an excess amount of bipyridyl and a stoichiometric amount of the nickel(II) bromide were present. The resulting polyketones (8a, 8b) have sufficiently high molecular weight (inherent viscosity: 0.59 dL/g for polyketone 8a; 0.35 dL/g for polyketone 8b) and a highly amorphous nature with a rather high glass transition temperature: 218 °C for polyketone 8a; 192 °C for polyketone 8b.

Crystal Structure, Thermal Behavior and Enzymatic Degradation of Poly(tetramethylene adipate) Solution-Grown Chain-Folded Lamellar Crystals

Abstract: Solution-grown chain-folded lamellar single crystals of poly(tetramethylene adipate) (PTMA) were prepared from a dilute solution of 2-methyl-I-propanol by isothermal crystallization. PTMA crystals were hexagonal-shaped and polyethylene decoration of the crystals resulted in a six cross-sector surface morphology and showed that the average direction of chain folding is parallel to the crystal growth planes of {110} and {010}. Chain-folded lamellar crystals gave well-resolved electron diffraction diagrams corresponding to all the equatorial reflections of the X-ray fiber diagram obtained from stretched PTMA melt-quenched film (β structure). The unit cell parameters of the β' structure of PTMA were determined as a = 0.503 nm, b = 0.732 nm and c (fiber axis) = 1.442 nm with an orthorhombic crystal system. The fiber repeat distance is appropriate for an all-trans backbone conformation for the straight stems. The setting angle, with respect to the a axis, is ±46° for the corner and center chains. Thermal behavior of lamellar crystals has been investigated by means of transmission electron microscopy (TEM) and atomic force microscopy (AFM). The lamellar thickness at the edges of the crystal increased after thermal treatment with taking the molecular chains into recrystallization parts; the holes then opened up at the thickening front of the crystal. The morphological changes of lamellar crystals after enzymatic degradation by Lipase type XIII from Pseudomonas sp. and water-soluble products were characterized by TEM, AFM, gel permeation chromatography, high performance liquid chromatography and fast atom bombardment mass spectrometry. The degradation progressed mainly from the edges of the lamellar crystals without decreasing the molecular weights and the lamellar thicknesses. The central portion of single crystals was often degraded by enzymatic attacks. This result combined with thermal behavior indicates that the loosely chain-packing region exists inside the single crystal, and that molecular chains in this region have higher mobility against thermal and enzymatic treatments.

The application of cyclobutane derivatives in organic synthesis.

Abstract: I. Introduction 1485II. Scope of This Review 1485III. Transformations of Cyclobutane Derivatives inOrganic Syntheses1486A. Ring-Opening Reactions 1486B. Ring-Contraction Reactions 1493C. Ring-Expansion Reactions 14951. Five-Membered Rings 14952. Six-Membered Rings 15093. Seven-Membered Rings 15174. Eight-Membered Rings 15215. Nine-Membered Rings 1523IV. Transformations of Cyclobutane Derivatives inNatural Product Syntheses1524A. Ring-Opening Reactions 1524B. Ring-Expansion Reactions 15261. Five-Membered Rings 15262. Six-Membered Rings 15293. Seven-Membered Rings 15324. Eight-Membered Rings 1533V. Conclusion 1534VI. Acknowledgments 1534VII. References 1534