We report a new fabrication method of a thin polymer film with regular array of micropores (honeycomb
film). A honeycomb film was fabricated by depositing a dilute solution of an amphiphilic polymer on water
surface. The honeycomb film transferred onto a solid substrate was characterized by atomic force microscopy.
By this fabrication method, it was possible to control film area, pore diameter, and film thickness. The
pore size depended upon the evaporation time of the polymer solution spread on water surface. The thickness
of a honeycomb film was controlled by spreading area of the polymer solution. The spreading behavior was
influenced by the water temperature. The film area was proportional to the volume of spread polymer
solution and controlled by changing the sub-phase temperature, too. When the polymer solution was
simply cast on a solid substrate, a thin polymer layer remained in the bottom of the honeycomb pores. On
the other hand, the honeycomb film fabricated on water surface has no bottom layer in its pores. A self-standing honeycomb mesh is formed by the “on-water spreading” method.
Catalytic asymmetric cyanations of
prochiral unsaturated compounds
affording the corresponding nitrile products in high enantiomeric
excess (≥90% in general) are summarized in this review. The
nucleophilic cyanide addition onto aldehydes, ketones, and imines
is promoted by chiral metal complexes and organocatalysts. Recent
progress in asymmetric conjugate cyanation of α,β-unsaturated
carbonyl compounds is also discussed. The asymmetric cyanation of
unactivated alkenes is catalyzed by chiral transition-metal complexes.
Current topics of intramolecular carbocyanation and aminocyanation
in addition to the traditional hydrocyanation are reviewed.
LiCl acts as a highly effective catalyst for cyanosilylation of various aldehydes and ketones to the corresponding silylated cyanohydrins. The reaction proceeds smoothly with a substrate/catalyst molar ratio of 100-100,000 at 20-25 degrees C under solvent-free conditions. alpha,beta-Unsaturated aldehydes are completely converted to the 1,2-adducts. The cyanation products can be isolated by direct distillation of the reaction mixture.
Palladium nanoparticles are prepared from palladium(II) acetate and 2 equivalents of potassium tert-butoxide in the presence of 4-octyne. The palladium nanoparticles-tetrabutylammonium borohydride system shows excellent catalytic activity and selectivity in the semihydrogenation of alkynes to the [(Z)-]alkenes. The hydrogenation of 4-octyne is conducted with the catalyst system at a substrate-to-palladium molar ratio of 10,000-200,000 under 8 atm of hydrogen to give (Z)-4-octene in > 99% yield. Isomerization and over-reduction of the Z-alkene are very slow even after consumption of the alkyne.
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