Regiospecific Glycosidation of Unprotected Sugars via Arylboronic Activation

Regiospecific Glycosidation of Unprotected Sugars via Arylboronic Activatio

Immobilization of a Soluble Metal Complex in an Organic Network. Remarkable Catalytic Performance of a Porous Dialkoxyzirconium Polyphenoxide as a Functional Organic Zeolite Analogue

Treatment of anthracenebisresorcinol 1 (a tetraphenol) with Zr(OtBu)4 in THF results in polycondensation to give an O−Zr−O network and affords a poly(dialkoxyzirconium phenoxide), 14-·2[Zr(OtBu)2] (Zr host), in quantitative yield as an insoluble, amorphous, microporous powder with a particle size of ∼0.7 μm, a pore size of ∼0.7 nm, and a specific surface area of ∼200 m2/g. The powder exhibits reversible Langmuir-type adsorption/desorption of N2 at 77 K and hexane at 298 K. Adsorption and coadsorption of ethyl acetate, benzene, and other polar and apolar guests also occurs readily at 298 K. The Zr host catalyzes the Diels−Alder reaction of acrolein with 1,3-cyclohexadiene in a remarkable manner. As a solid metal−organic catalyst, it has a formula-based turnover rate constant of 40 h-1, which far exceeds those of its components, i.e., the soluble Lewis acid Zr(OtBu)4 (0.1 h-1) and the hydrogen-bonded insoluble organic network 1 (0.3 h-1). The solid catalyst can be easily separated from the organic product, which is not contaminated with Zr or the reactants. The recovered catalyst can be used repeatedly without deactivation. The reaction can also be conducted in a flow system with the insoluble Zr host catalyst and a reactant mixture as a mobile phase. The remarkable catalytic performance of the Zr host and its easy preparation suggest that insoluble microporous metal−organic solid catalysts are workup-free and waste-free as well as resource- and energy-saving

Helical Coordination Polymers from Achiral Components in Crystals. Homochiral Crystallization, Homochiral Helix Winding in the Solid State, and Chirality Control by Seeding

An achiral anthracene−pyrimidine derivative (5-(9-anthracenyl)pyrimidine, 1) forms adduct 1·Cd(NO3)2·H2O·EtOH (2) in chiral space group P21. The metal ion is hexacoordinated with two pyrimidine ligands (equatorial cis), water and ethanol (equatorial cis), and two nitrate ions (axial trans). The chirality arises from a pyrimidine−Cd2+ helical array and is preserved not only in each crystal via homochiral interstrand water−nitrate hydrogen bonding but also in all the crystals in the same chirality as a result of single-colony homochiral crystal growth. Compound 1 also forms achiral (Pbca) trihydrate adduct 1·Cd(NO3)2·3H2O (3) having nonhelical pyrimidine−Cd2+ zigzag chains. Achiral zigzag polymer 3 and chiral helical polymer 2 are interconvertible with each other in the solid states upon exchange of volatile ligands (ethanol and water). The helix winding associated with the conversion of adduct 3 to 2 can be made homochiral by seeding

Acridinylresorcinol as a Self-Complementary Building Block of Robust Hydrogen-Bonded 2D Nets with Coordinative Saturation. Preservation of Crystal Structures upon Guest Alteration, Guest Removal, and Host Modification

Acridinylresorcinol host 3 (9-(3,5-dihydroxy-1-phenyl)acridine) forms such adducts as 3·(benzene), 3·(chloroform), 3·0.5(toluene), and 3·(isobutyl benzoate). Modified acridinol host 4 (9-(3,5-dihydroxy-1-phenyl)-4-hydroxyacridine) having an additional OH group on the acridine ring affords such adducts as 4·(benzene), 4·(chloroform), 4·0.5(toluene)·0.5(water), 4·(methanol)·(water), and 4·(ethyl acetate). In the crystals, hosts 3 and 4 form hydrogen-bonded (O−H···O−H) poly(resorcinol) chains which are linked together via interchain O−H···N hydrogen bonds to give a coordinatively saturated (O−H···O−H···N) 2D net composed of doubly hydrogen-bonded and antiparallel-stacked, self-complementary cyclic dimer 32 or 42 as a rigidified building block, the otherwise flexible O−H···O−H hydrogen bonds being thereby taken in a cyclophane-like structure. This network turns out to be remarkably well preserved among the above adducts. Guest molecules, which are disordered in many cases, are incorporated in the cavities left. The binding of small polar guests to host 4 is primarily due to hydrogen bonding to the OH group on the acridine ring. The latter therefore acts only as a polarity modifier of preserved cavities. Adduct 3·(benzene), that is, 32·2(benzene) readily loses one of two guest molecules bound in each cavity to give a microporous half-filled adduct 32·(benzene) which adsorbs 1 mol of benzene to regenerate the starting full adduct without involving a phase change, as confirmed by X-ray powder diffractions and reversible Langmuir-type adsorption/desorption isotherms. The self-complementarity strategy for designing rigid crystal structures is discussed with a particular reference to the possibility of systematic perturbation/variation approaches in crystal engineering

Dynamic Aspects of Lattice Inclusion Complexation Involving a Phase Change. Equilibrium, Kinetics, and Energetics of Guest-Binding to a Hydrogen-Bonded Flexible Organic Network

The solid/gas complexation of anthracenebisresorcinol host (1) and ethyl acetate as a guest was monitored by pressure-decay, X-ray powder diffraction, and gravimetric/calorimetric thermal desorption analyses. It involves an exothermic (∼30 kcal/mol) phase transition and exhibits “vertical” adsorption as well as desorption “isotherms” at a threshold (equilibrium) pressure (Pth) of the guest vapor. This is in accord with the phase rule for a two-component/three-phase/one-freedom system. The activation energies of adsorption and desorption are 2.3 and 34 kcal/mol, respectively; desorption at 25 °C takes weeks. The crystal structure of the ethyl acetate adduct illustrates how the flexible hydrogen-bonded network of host 1 adjusts itself to the small guest. Other polar guests (ester, ketone, and alcohol) behave similarly and give rise to desorption-resistant stable adducts, except for the least bulky members of the ester and ketone guests, i.e., methyl acetate and acetone. The mechanism of phase transition is discussed in light of the lack of size effect as for the host and well-behaved guest-prebinding at P Pth

Dynamic Aspects of Lattice Inclusion Complexation Involving a Phase Change. Equilibrium, Kinetics, and Energetics of Guest-Binding to a Hydrogen-Bonded Flexible Organic Network

The solid/gas complexation of anthracenebisresorcinol host (1) and ethyl acetate as a guest was monitored by pressure-decay, X-ray powder diffraction, and gravimetric/calorimetric thermal desorption analyses. It involves an exothermic (∼30 kcal/mol) phase transition and exhibits “vertical” adsorption as well as desorption “isotherms” at a threshold (equilibrium) pressure (Pth) of the guest vapor. This is in accord with the phase rule for a two-component/three-phase/one-freedom system. The activation energies of adsorption and desorption are 2.3 and 34 kcal/mol, respectively; desorption at 25 °C takes weeks. The crystal structure of the ethyl acetate adduct illustrates how the flexible hydrogen-bonded network of host 1 adjusts itself to the small guest. Other polar guests (ester, ketone, and alcohol) behave similarly and give rise to desorption-resistant stable adducts, except for the least bulky members of the ester and ketone guests, i.e., methyl acetate and acetone. The mechanism of phase transition is discussed in light of the lack of size effect as for the host and well-behaved guest-prebinding at P Pth

Dynamic Aspects of Lattice Inclusion Complexation Involving a Phase Change. Equilibrium, Kinetics, and Energetics of Guest-Binding to a Hydrogen-Bonded Flexible Organic Network

The solid/gas complexation of anthracenebisresorcinol host (1) and ethyl acetate as a guest was monitored by pressure-decay, X-ray powder diffraction, and gravimetric/calorimetric thermal desorption analyses. It involves an exothermic (∼30 kcal/mol) phase transition and exhibits “vertical” adsorption as well as desorption “isotherms” at a threshold (equilibrium) pressure (Pth) of the guest vapor. This is in accord with the phase rule for a two-component/three-phase/one-freedom system. The activation energies of adsorption and desorption are 2.3 and 34 kcal/mol, respectively; desorption at 25 °C takes weeks. The crystal structure of the ethyl acetate adduct illustrates how the flexible hydrogen-bonded network of host 1 adjusts itself to the small guest. Other polar guests (ester, ketone, and alcohol) behave similarly and give rise to desorption-resistant stable adducts, except for the least bulky members of the ester and ketone guests, i.e., methyl acetate and acetone. The mechanism of phase transition is discussed in light of the lack of size effect as for the host and well-behaved guest-prebinding at P Pth

Dynamic Aspects of Lattice Inclusion Complexation Involving a Phase Change. Equilibrium, Kinetics, and Energetics of Guest-Binding to a Hydrogen-Bonded Flexible Organic Network

The solid/gas complexation of anthracenebisresorcinol host (1) and ethyl acetate as a guest was monitored by pressure-decay, X-ray powder diffraction, and gravimetric/calorimetric thermal desorption analyses. It involves an exothermic (∼30 kcal/mol) phase transition and exhibits “vertical” adsorption as well as desorption “isotherms” at a threshold (equilibrium) pressure (Pth) of the guest vapor. This is in accord with the phase rule for a two-component/three-phase/one-freedom system. The activation energies of adsorption and desorption are 2.3 and 34 kcal/mol, respectively; desorption at 25 °C takes weeks. The crystal structure of the ethyl acetate adduct illustrates how the flexible hydrogen-bonded network of host 1 adjusts itself to the small guest. Other polar guests (ester, ketone, and alcohol) behave similarly and give rise to desorption-resistant stable adducts, except for the least bulky members of the ester and ketone guests, i.e., methyl acetate and acetone. The mechanism of phase transition is discussed in light of the lack of size effect as for the host and well-behaved guest-prebinding at P Pth

Acridinylresorcinol as a Self-Complementary Building Block of Robust Hydrogen-Bonded 2D Nets with Coordinative Saturation. Preservation of Crystal Structures upon Guest Alteration, Guest Removal, and Host Modification

Acridinylresorcinol host 3 (9-(3,5-dihydroxy-1-phenyl)acridine) forms such adducts as 3·(benzene), 3·(chloroform), 3·0.5(toluene), and 3·(isobutyl benzoate). Modified acridinol host 4 (9-(3,5-dihydroxy-1-phenyl)-4-hydroxyacridine) having an additional OH group on the acridine ring affords such adducts as 4·(benzene), 4·(chloroform), 4·0.5(toluene)·0.5(water), 4·(methanol)·(water), and 4·(ethyl acetate). In the crystals, hosts 3 and 4 form hydrogen-bonded (O−H···O−H) poly(resorcinol) chains which are linked together via interchain O−H···N hydrogen bonds to give a coordinatively saturated (O−H···O−H···N) 2D net composed of doubly hydrogen-bonded and antiparallel-stacked, self-complementary cyclic dimer 32 or 42 as a rigidified building block, the otherwise flexible O−H···O−H hydrogen bonds being thereby taken in a cyclophane-like structure. This network turns out to be remarkably well preserved among the above adducts. Guest molecules, which are disordered in many cases, are incorporated in the cavities left. The binding of small polar guests to host 4 is primarily due to hydrogen bonding to the OH group on the acridine ring. The latter therefore acts only as a polarity modifier of preserved cavities. Adduct 3·(benzene), that is, 32·2(benzene) readily loses one of two guest molecules bound in each cavity to give a microporous half-filled adduct 32·(benzene) which adsorbs 1 mol of benzene to regenerate the starting full adduct without involving a phase change, as confirmed by X-ray powder diffractions and reversible Langmuir-type adsorption/desorption isotherms. The self-complementarity strategy for designing rigid crystal structures is discussed with a particular reference to the possibility of systematic perturbation/variation approaches in crystal engineering

Effects of Hydration on Mechanical Properties of Acylated Hydroxyapatite–Starch Composites

Transesterification of vinyl acetate, vinyl benzoate, and vinyl laurate with hydroxyapatite–starch composites was carried out in dimethyl sulfoxide at 25–120 °C for 8 h. The composites of acylated starch and hydroxyapatite were compressed by hot pressing at 60 °C or 120 °C at 120 MPa to obtain the compacts. The three-point bending test of the compressed compacts revealed that acetylation and benzoylation did not alter the mechanical properties of the composites much, while lauroylation softened the composites. Bending elastic moduli of the acetylated and benzoylated composites were 2–3 GPa, whereas those of the lauroylated composites were 0.1–0.3 GPa. Both hydroxyapatite–starch compacts and their acetylated ones readily collapsed in the bending test after immersion in water, while the benzoylated and lauroylated composite compacts were water-resistant. The bending strengths of the compacts of benzoylated and lauroylated composites after immersion in water were ca. 60–75% of those of the pristine compacts. The stain at break of the lauroylated composites after immersion in water was 1.1–1.75 times larger than that of the as-prepared onestrends similar to natural bone