A general synthesis of s-triazolo[1,5-x] diazines

Treatment of 2-aminopyrimidime, a 4-aminopyrimidine, aminopyrazine, and 3-aminopyridazines with O-mesilylenesulfonylhydroxylamine gave the corresponding N-aminodiazinium salts in high yields. These salts could be transformed into s-triazolo[1, 5-a] pyrimidines, s-triazolo[1, 5-a]-pyrazines, s-triazolo[1, 5-c]pyrimidines, and s-triazolo[1, 5-b]pyridazines hy treatment with acylating agents.     

Synthesis and properties of organic–inorganic hybrid liquid crystal gels

Organic–inorganic hybrid liquid crystal (LC) gels have been synthesised by the thiol-ene reaction of a multifunctional cyclic siloxane, 1,3,5,7-tetravinyl-1,3,5,7-tetramethylcyclotetrasiloxane (TVMCTS) and alkane dithiols, 1,6-hexanedithiol (HDT) or 1,9-decanedithiol (DDT), in LC matrices, 4-cyano-4?-pentylbiphenyl (5CB) or 4′-n-octyl-4-cyano-biphenyl (8CB). The LC gels were prepared in an isotropic phase at 70°C or mesophases at 25°C using radical initiators. The phase transition temperatures from a mesophase to an isotropic phase of the resulting gels were lower than those of the original LCs. The gels containing 8CB (8CB gels) prepared at 25°C showed two phase transitions: smectic-to-nematic and nematic-to-isotropic transitions. By contrast, the 8CB gels synthesised in the isotropic phase showed only one phase transition from smectic phase directly to isotropic phase. Reaction conversions in the LC gels prepared at 70°C were higher than that in the gels prepared at 25°C. Scanning microscopic light scattering analysis of the LC gels cleared homogeneous small size mesh with a small amount of large defect. Polarisation micrographs of the LC gels showed framed optical textures derived from the LC molecules at room temperature. The LC gels containing more than 90 wt% of LC showed electro-optic response.     

Basic study of ℜ-semigroups and their homomorphisms

In this paper we study ?-semigroups from the standpoint of their homomorphisms into the semigroup IR of positive real numbers under addition. Every ?⁺-semigroup S is isomorphic with a subdirect product of a structure group G and a semigroup of positive real numbers. It is determined by G and a positive real valued function cp on G. We also study the semigroup Hom(S,T) of homomorphisms of an ?-semigroup S into another ?-semigroup T. Each element of Hom(S,T) can be described in terms of an element of Hom(S,IR₊) and an element of Hom(S,H) where H is a structure group of T.     

Systematic Experiment on Star Anomaly in pd Break up at E/A = 9.5 MeV

We measured pd breakup cross section at E _d = 19 MeV (E/A = 9.5 MeV) at Star configuration at 120° ≤ inclination angle α ≤ 180°, i.e. apart from Space Star configuration (α = 90°), and found that pd Star cross section at 120° ≤ α ≤ 180° agree with pd calculation, contrary to Köln data. By our systematic experiments on Star configurations so far and recent reliable pd calculations, existence of Space Star anomaly has been established in pd breakup at E/A = 9.5 and 13 MeV. Also it has been confirmed that no anomaly exist at Star configurations apart from Space Star.     

Factors Controlling Stereoselectivity in the Koenigs-Knorr Type D-Mannopyranosylation

Abstract

The factors controlling stereoselectivity in the formation of cyclohexyl α- and β-D-mannopyranosides with D-mannosyl chloride, cyclohexanol and silver triflate (AgOTf), were examined. For the syntheses of β-D-mannopyranosides, dichloromethane (CH₂Cl₂) as solvent could be used only at low temperature, while the use of tetrahydrofuran (THF) as solvent proved to be effective at room temperature. Diallyl ether (All₂O) was effectively used in CH₂Cl₂ as an olefinic additive. Stereoselectivities in these reactions were changed by use of THF as an oxonium ion source and All₂O as an inhibitor to prevent complex formation of the silver ion with the allyloxy group of the glycosyl donor.     

One-pot reactions of bicyclic zinc enolate generated from Ni-catalyzed reductive cyclization to furnish octahydro-4,7-ethanobenzofuran-9-one derivatives

The one-pot reactions of catalytically generated bicyclic zinc enolate with various electrophiles are reported. The zinc enolate as a key intermediate is efficiently delivered from Ni-catalyzed reductive cyclization of alkynyl cyclohexadienone. Employing aldehydes, imine, nitroalkene, and α,β-unsaturated carbonyl compounds as electrophiles, this new class of one-pot reactions gave multi-functionalized cis-hydrobenzofurans and octahydro-4,7-ethanobenzofuran-9-one derivatives in moderate to good yields.     

Storage of CO2 into Porous Coordination Polymer Controlled by Molecular Rotor Dynamics

Design to store gas molecules, such as CO₂, H₂, and CH₄, under low pressure is one of the most important challenges in chemistry and materials science. Herein, we describe the storage of CO₂ in the cavities of a porous coordination polymer (PCP) using molecular rotor dynamics. Owing to the narrow pore windows of PCP, CO₂ was not adsorbed at 195 K. As the temperature increased, the rotors exhibited rotational modes; such rotations dynamically expanded the size of the windows, leading to CO₂ adsorption. The rotational frequencies of the rotors (k≈10^?6 s) and correlation times of adsorbed CO₂ (τ≈10^?8 s) were elucidated via solid‐state NMR studies, which suggest that the slow rotation of the rotors sterically restricts CO₂ diffusion in the pores. This restriction results in an unusually slow CO₂ mobility close to solid state (τ≥10^?8 s). Once adsorbed at room temperature, CO₂ is robustly stored in the PCP under vacuum at 195–233 K because of the steric hindrance of the rotors. We also demonstrate that this mechanism can be applied to the storage of CH₄.     

Redox-induced conformational alteration of n,n-diarylamides

We constructed a novel molecular conformational alteration system with an N-aryl-N-phenylacetamide structure, in which the N-aryl group consists of a hydroquinone-p-quinone system as a redox-dependent aromatic trigger. The amide conformation depended on the oxidation state of the aryl group, and the two states (compounds 2 and 3) were reversibly converted to each other by redox reactions. Such compounds would be applied as useful structural units for external stimulus-responsive control on the shape and function of large molecules or supramolecules.     

Enantioselective syntheses of various chiral multicyclic compounds with quaternary carbon stereocenters by catalytic intramolecular cycloaddition

The intramolecular cycloaddition of 1,n-diene-ynes (n = 4-6), where alkyne and alkene moieties are connected by a 1,1-disubstituted alkene, was examined using a chiral rhodium catalyst, and various types of cycloadducts with quaternary carbon stereocenter(s) were obtained in high to excellent enantiomeric excess. In the case of 1,4-diene-ynes, tricyclic, bicyclic, and spirocyclic compounds were obtained depending upon the substituents at the 2-position of the 1,4-diene moiety and those at their alkyne termini. On the other hand, 1,5- and 1,6-diene-ynes gave tricyclic and bicyclic compounds, which included medium-sized ring systems. The mechanistic considerations for different reaction pathways and the synthetic transformation of tricyclic products into functionalized spirocyclic compounds are also described. The reaction of enediynes, where two alkyne moieties are connected by a 1,1-disubstituted alkene, was also examined, and sterically strained tricyclic compounds with two carbon stereocenters were obtained.