Use of triazole-ring formation to attach a Ru/TsDPEN complex for asymmetric transfer hydrogenation to a soluble polymer

The cycloaddition of a chiral ligand containing a terminal alkyne to a soluble polymer containing an azide provides a convenient means for the attachment of an asymmetric transfer hydrogenation catalyst to a soluble polymer support. Using these ligands in complexes with Ru(II), gave good results in terms of conversion and enantioselectivity (up to 95% ee) in ketone reduction reactions.     

Synthesis and reduction reactions of pyridones and 5-acyl-2-methoxypyridines

The synthesis of a series of pyridones, from their 2-hydroxypyridine or 2-methoxypyridine precursors, is described, along with studies into their reductions to saturated heterocycles. A number of 5-acylpyridones were prepared and were evaluated as substrates for asymmetric transfer hydrogenation prior to conversion to saturated heterocycles. The enantioselective reduction of 5-acetyl-1-benzylpyrimidine-2,4(1H,3H)-dione is also described.     

Mirror‐Image Organometallic Osmium Arene Iminopyridine Halido Complexes Exhibit Similar Potent Anticancer Activity

Four chiral Os^II arene anticancer complexes have been isolated by fractional crystallization. The two iodido complexes, (S_Os,S_C)‐[Os(η⁶‐p‐cym)(ImpyMe)I]PF₆ (complex 2 , (S)‐ImpyMe: N‐(2‐pyridylmethylene)‐(S)‐1‐phenylethylamine) and (R_Os,R_C)‐[Os(η⁶‐p‐cym)(ImpyMe)I]PF₆ (complex 4 , (R)‐ImpyMe: N‐(2‐pyridylmethylene)‐(R)‐1‐phenylethylamine), showed higher anticancer activity (lower IC₅₀ values) towards A2780 human ovarian cancer cells than cisplatin and were more active than the two chlorido derivatives, (S_Os,S_C)‐[Os(η⁶‐p‐cym)(ImpyMe)Cl]PF₆, 1 , and (R_Os,R_C)‐[Os(η⁶‐p‐cym)(ImpyMe)Cl]PF₆, 3 . The two iodido complexes were evaluated in the National Cancer Institute 60‐cell‐line screen, by using the COMPARE algorithm. This showed that the two potent iodido complexes, 2 (NSC: D‐758116/1) and 4 (NSC: D‐758118/1), share surprisingly similar cancer cell selectivity patterns with the anti‐microtubule drug, vinblastine sulfate. However, no direct effect on tubulin polymerization was found for 2 and 4 , an observation that appears to indicate a novel mechanism of action. In addition, complexes 2 and 4 demonstrated potential as transfer‐hydrogenation catalysts for imine reduction.     

Data sampling and data recovery

The sampling theorem states that a continuous signal can always be reconstructed from an equi-spaced set of samples of the signal, as long as the sampling rate has been chosen in accordance with the Nyquist criterion, thus allowing economical use of sampling rate and data storage. The practical aspects of data reconstruction from such sets of samples are considered.     

Plastic deformation of polypropylene: Effect of molecular weight on drawing behavior and structural characteristics of ultra-high-modulus products

The influence of molecular weight and temperature on the tensile drawing behavior of polypropylene has been studied, with particular reference to the production of ultra-high-modulus oriented materials. It has been shown that the optimum draw temperature is molecular weight independent to a good approximation, and that high-modulus products can be obtained for M?_w in the range 180,000–400,000, the highest modulus being achieved for polymer with M?_w = 181,000. As in the case of linear polyethylene, under optimum drawing conditions the Young's modulus relates only to the draw ratio. Low-temperature moduli as high as 25–27 GPa were recorded, which compare favorably with a previously reported value of 42 GPa for the crystal-lattice modulus. Although the drawing behaviour of the samples studied appeared comparatively insensitive to molecular weight, some of the properties of the draw materials, notably melting point and shrinkage at high temperature, showed a wide range of behavior.     

Alkaline earth metal complexes of a phosphine-borane-stabilized carbanion: synthesis, structures, and stabilities

The reaction between either MgI2 or CaI2 and 2 equiv of [(Me3Si)2{Me2(H3B)P}C]K (2) in toluene gives the corresponding organo-alkaline earth metal compounds [(Me3Si)2{Me2(H3B)P}C]2M in moderate to good yields [M = Mg (3), Ca (4)]. Compound 3 crystallizes solvent-free, whereas X-ray quality crystals of 4 could not be obtained in the absence of coordinating solvents; crystallization of 4 from cold methylcyclohexane/THF gives the solvate [(Me3Si)2{Me2(H3B)P}C]2Ca(THF)4 (4a). The corresponding heavier alkaline earth metal complexes [(Me3Si)2{Me2(H3B)P}C]2M(THF)5 [M = Sr (7), Ba (8)] are obtained from the reaction between MI2 and 2 equiv of 2 in THF, followed by recrystallization from cold methylcyclohexane/THF. Compound 3 degrades over a period of several weeks at room-temperature both in the solid state and in toluene solution to give the free phosphine-borane (Me3Si)2{Me2(H3B)P}CH (5) as the sole phosphorus-containing product. In addition, compounds 3, 4, and 4a react rapidly with THF in toluene solution, yielding 5 as the sole phosphorus-containing product; in contrast, compounds 7 and 8 are stable toward this solvent.