Photoinduced Atom Transfer Radical Addition/Cyclization Reaction between Alkynes or Alkenes with Unsaturated α-Halogenated Carbonyls

We have developed a photochemical ATRA/ATRC reaction that is mediated by halogen bonding interactions. This reaction is caused by the reaction of malonic acid ester derivatives containing bromine or iodine with unsaturated compounds such as alkenes and alkynes in the presence of diisopropylethylamine under visible light irradiation. As a result of various control experiments, it was found that the formation of complexes between amines and halogens by halogen-bonding interaction occurs in the reaction system, followed by the cleavage of the carbon–halogen bonds by visible light, resulting in the formation of carbon radicals. In this reaction, a variety of substrates can be used, and the products, cyclopentenes and cyclopentanes, were obtained by intermolecular addition and intramolecular cyclization.     

One-Handed Helical Tubular Ladder Polymers for Chromatographic Enantioseparation**

Defect-free one-handed contracted helical tubular ladder polymers with a π-electron-rich cylindrical helical cavity were synthesized by alkyne benzannulations of the random-coil precursor polymers containing 6,6′-linked-1,1′-spirobiindane-7,7′-diol-based chiral monomer units. The resulting tightly-twisted helical tubular ladder polymers showed remarkably high enantioseparation abilities toward a variety of chiral hydrophobic aromatics with point, axial, and planar chiralities. The random-coil precursor polymer and analogous rigid-rod extended helical ribbon-like ladder polymer with no internal helical cavity exhibited no resolution abilities. The molecular dynamics simulations suggested that the π-electron-rich cylindrical helical cavity formed in the tightly-twisted tubular helical ladder structures is of key importance for producing the highly-enantioseparation ability, by which chiral aromatics can be enantioselectively encapsulated by specific π-π and/or hydrophobic interactions.     

Peculiar ‘Reptational’ Movements of Single Synthetic Polymer Chains on Substrate Observed by AFM

Peculiar ‘reptational’ movements of isotactic PMMA chains on mica are observed by in situ AFM. The polymer molecules comprise long flexible chains that exhibit reptative, or snake‐like, motion on the substrate along the direction of the polymer chain. Intriguingly, some chains underwent forward then backward motion in which the head of the chain moved in a curvilinear manner along the previous contours of the polymer chain. No limitation in the direction of movement for the ends of the polymer chain was anticipated based on an assumed reptational mechanism. As a result, the chains recovered a conformation that had been adopted prior to the initial movement. Several factors that may affect the movement are discussed.

     

Synthesis,Structures, and Complexation with Phenolic Guests of Acridone-Incorporated Arylene–Ethynylene Macrocyclic Compounds

Acridone units were incorporated into the arylene–ethynylene structure as polar arene units. Cyclic trimers consisting of three acridone-2,7-diyl units and three 1,3-phenylene units were synthesized by Sonogashira couplings via stepwise or direct route. X-ray analysis revealed that the trimer had a nearly planar macrocyclic framework with a cavity surrounded by three carbonyl groups. In contrast, the corresponding tetramer had a nonplanar macrocyclic framework. ¹H NMR measurements showed that the trimer formed a 1 : 1 complex as a macrocyclic host with dihydric phenol guests, and the association constants were determined to be ca. 1.0×10³ L mol⁻¹ for hydroquinone or resorcinol guests in CDCl₃ at 298 K. The calculated structures of these complexes by the DFT method supported the presence of two sets of OH⋅⋅⋅O=C hydrogen bonds between the host and guest molecules. The spectroscopic data of the cyclic trimers and tetramers are compared with those of reference acridone compounds.     

Macromolecular helicity inversion of poly(phenylacetylene) derivatives induced by various external stimuli

Unique macromolecular helicity inversion of stereoregular, optically active poly(phenylacetylene) derivatives induced by external achiral and chiral stimuli is briefly reviewed. Stereoregular, cis-transoidal poly(phenylacetylene)s bearing an optically active substituent, such as (1R,2S)-norephedrine (poly- 1 ) and β-cyclodextrin residues (poly- 2 ), show an induced circular dichroism (ICD) in the UV-visible region of the polymer backbone in solution due to a predominantly one-handed helical conformation of the polymers. However, poly- 1 undergoes a helix-helix transition upon complexation with chiral acids having an R configuration, and the complexes exhibit a dramatic change in the ICD of poly- 1 . Poly- 2 also shows the inversion of macromolecular helicity responding to molecular and chiral recognition events that occurred at the remote cyclodextrin residues from the polymer backbone; the helicity inversion is accompanied by a visible color change. A similar helix-helix transition of poly((R)- or (S)-(4-((1-(1-naphthyl)ethyl)carbamoyl)phenyl)acetylene) is also briefly described.     

Supported Noble Metal Catalysts and Adsorbents with Soft Lewis Acid Functions

Heterogeneous noble metal catalysts exhibit various functions. Although their redox functions have been extensively studied, we focused on their soft Lewis acid functions. Supported Au, Pt, and Pd catalysts electrophilically attack the π-electrons of soft bases such as alkynes, alkenes, and aromatic compounds to perform addition and substitution reactions. Hydroamination, intramolecular cyclization of alkynyl carboxylic acids, isomerization of allylic esters, vinyl exchange reactions, Wacker oxidation, and oxidative homocoupling of aromatics are introduced based on a discussion of the active species and reaction mechanisms. Furthermore, the adsorption of sulfur compounds, which are soft bases, onto the supported AuNPs is discussed. The adsorption and removal of 1,3-dimethyltrisulfane (DMTS), which is the compound responsible for the stale odor of “hine-ka” in alcoholic beverages, particularly Japanese sake, is described.