Intramolecular Diels-Alder reactions of ester-tethered 1,7,9-decatrienoates: bis[chloro(methyl)aluminum]trifluoromethanesulfonamide as a catalyst

[reaction: see text] The intramolecular Diels-Alder reaction of 1,7,9-decatrienoate derivative with an ester tether is efficiently catalyzed by the bidentate Lewis acid, bis-aluminated trifluoromethanesulfonamide.     

Prostaglandin synthesis from a fulvene with the ω-side chain equivalent

The acid-catalyzed hydrolysis of the Diels-Alder adduct of 6-(2,2-ethylene-dioxyheptyl) fulvene with 2-chloroacrylonitrile gave 7-anti-(3-oxo-1-trans-octenyl)-2-chloro-2-cyanobicyclo[2.2.1]hept-5-ene, which is an intermediate of 12-epi-prostaglandine. On the other hand, the hydrolysis of 7-(3,3-ethylenedioxyoctylidene)bicyclo-[2.2.1]hept-5-en-2-one, obtained from the Diels-Alder adduct of the fulvene with 2-chloroacryloyl chloride, gave a mixture (3:2) of 7-anti- and 7-syn-(3-oxo-1-trans-octenyl)bicyclo[2.2.1]hept-5-en-2-one. The latter compound was oonverted into prostaglandin F_2α.     

Fracture,fatigue and yielding of materials as a stochastic process

Conclusion It is very interesting that stochastic process model, paying no speculation on detailed atomic mechanisms, can be applied reasonably in many types of fracture and failure of metallic and non-metallic materials. Especially in the case of yielding of mild steel, the experimental results are in good agreement with the prediction of the theory as a stochastic process based on the present dislocation theory in terms of atomic mechanism. This indicates that general concepts of the stochastic process theory of yielding of mild steel as well as the dislocation theory of yielding are correct. The experimental data available at the present time appear not sufficient to evaluate the relative merits of the several atomic theories proposed which may be constructed by employing different detailed dislocation models. Consequently, in this respect it would be very valuable to investigate the scatter characteristics of delay time for the initiation of yielding of mild steel under constant applied stress to check whether such eqn. [1] or [4] exists in this case or not, and to study the frequency distribution of upper yield stress at the constant rate of stress application at low temperatures.     

Piezoelectric relaxation in poly(γ-methyl-L-glutamate) at high temperature

Piezoelectric relaxation has been studied on elongated poly(γ-methyl-L-glutamate) films with the α-helical molecular conformation. Relaxation processes are observed near 0 and 100°C. Each process has a dual character composed of relaxational and retardational frequency dependences. The low-temperature process is ascribed to thermal motion of side chains. The high-temperature process, discussed in relation to the dielectric relaxation, is attributed to the ionic dc conduction connected with the two-phase structure of crystalline regions and the electrode polarization.     

Molecular weight determination of polyamides by vapor pressure osmometry

The vapor pressure osmometry method for determining the molecular weight of polyamides has been studied by use of the newly developed solvents. Polymers used were polycaprolactams, polyenanthamides, and polypelargonamides. The measurements were carried out with 2,2,3,3-tetrafluoro-1-propanol and 2,2,3,3,4,4,5,5,6,6,7,7-dodecafluoro-1-heptanol as solvents at 50 and 130°C., respectively. Endgroup determinations on samples were also done in m-cresol by 0.1 N-hydrochloric acid. Reduced resistance differences (ΔR/C)₀ obtained by vapor pressure osmometry at 50°C. were found to be in linear relation with the reciprocal of the number-average molecular weight determined by endgroup titrations; but anomalous results were obtained when dodecafluoroheptanol was used as the solvent at 130°C.     

Osmotic pressure control in response to a specific ion signal at physiological temperature using a molecular recognition ion gating membrane

A molecular recognition gating ion membrane was prepared by graft copolymerization of N-isopropylacrylamide and benzo[18]crown-6-acrylamide onto the pore surface of porous polyethylene film. This membrane captured Ba2+ with its crown ether receptors and generated osmotic pressure in response to Ba2+ autonomously and reversibly. However, the membrane never generated osmotic pressure in response to Ca2+. In addition, the concentration gradient of both the ion and other solute such as dextran could be used as the driving force; using a dextran concentration gradient, we can control the critical concentration and the duration time of the osmosis response.     

Total synthesis of (-)-aspidospermine via diastereoselective ring-closing olefin metathesis

An enantiocontrolled total synthesis of (-)-aspidospermine has been achieved. The key element of the strategy is the diastereoselective construction of the quaternary stereogenic center employing 1,4-asymmetric induction during the ring-closing olefin metathesis.