Morphology of poly(p‐oxybenzoyl) prepared in perfluoropolyether

Solvent effect on the morphology of poly(p‐oxybenzoyl) (POB) prepared by the reaction‐induced phase separation of oligomers was examined by the polymerization of p‐acetoxybenzoic acid in perfluoropolyether Aflunox^TM (AFL2507 and AFL606). Polymerization was carried out at 320°C for 6 hr. POB microspheres were formed in AFL2507 by the liquid–liquid phase separation of oligomers due to the low miscibility of oligomers in AFL2507. The molecular weight of the solvent influenced the morphology, and the polymerization in AFL606 of which the molecular weight was lower than AFL2507 yielded whiskers formed by crystallization of oligomers induced by the increase in miscibility compared with that in AFL2507. The solvent structure and its molecular weight influenced the miscibility of oligomers and ultimately controlled the morphology from whisker to microsphere. Copyright © 2004 John Wiley & Sons, Ltd.     

From Axial Chirality to Central Chiralities: Pinacol Cyclization of 2,2′-Biaryldicarbaldehyde to trans-9,10-Dihydrophenanthrene-9,10-diol

Two salient features —the stereoselectivity to give only the trans-diol, and the stereospecificity to transmit the axial chirality (in case the starting biphenyl is configurationally stable) onto two stereogenic centers of the product—characterize the pinacol cyclization of 2,2′-biaryldicarbaldehydes (see reaction). The accessibility of trans-9,10-dihydrophenanthrene-9,10-diols provides the new enantiopure C₂-symmetric diol 1 , which shows potential utility in asymmetric synthesis.     

Optical fiber coupling to single-mode silica-based planar lightwave circuits with fiber-guiding grooves

To enable alignmentfree optical fiber coupling to single-mode silica-based waveguides, fiber-guiding grooves are fabricated in the same substrate as waveguide circuits.These grooves are used successfully to couple optical fiber to Waveguides. An average, fiber-to-waveguide coupling loss of 0.6 dB per interface is obtained with eight arrayedguiding grooves, and it is expected that this will further be reduced to 0.2 dB per interface. The coupling loss varies by ±0.3 dB during thermal cycling between -10°C and +60°C.     

Cationic zirconocene- or hafnocene-based Lewis acids in organic synthesis: glycoside-flavonoid analogy

Cationic metallocene species, generated from Cp₂MCl₂ and AgClO₄ (M=Zr, Hf), were used for the glycosylation of catechin derivative 2, enabling a concise synthesis of a glycosyl flavonoid, astilbin (1). Further study revealed the efficiency of this Lewis acidic species for S_N1-type activation of the C(4) position of catechin derivative 11, enabling selective substitution with various nucleophiles.     

Synthetic study of phomoidride B (CP-263,114); utilization of the oxidopyrylium [5 + 2] cycloaddition

The highly functionalized core structure of phomoidride B (CP-263,114) was pursued by using intermolecular oxidopyrylium-alkene cyclization as one of the key steps.     

Directional solidification of InxGa1−xAs

We have investigated a constitutional supercooling and segregation phenomena in In_xGa_1−xAs crystals unidirectionally solidified in a vertical system. The constitutional supercooling generates characteristic fluctuations of composition along the growth direction and this can be explained by a free nucleation ahead from the growth interface. The macroscopic compositional profiles of the grown crystals suggest that a transport of solute is mainly dominated by the diffusion. Such a growth mode is partly attributed to the difference in density between InAs and GaAs.     

Toward Naphthocyclinones: Doubly Connected Octaketide Dimers with a Bicyclo[3.2.1]octadienone Core by Thiolate‐Mediated Cyclization

A viable method is reported for the synthesis of the bicyclo[3.2.1]octadienone scaffold in naturally occurring octaketide dimers. The procedure employs a reductive cyclization reaction mediated by an unusual ethanedithiol monosodium salt.     

Synthesis of an Optically Active Trisubstituted α,β-Butenolide, (S)-4, 6-Dihydroxy-2, 3-dimethyl-2-hexesoic Acid 1, 4-Lactone,from 2-Deoxy-D-ribose

The title compound has been synthesized efficiently from 2-deoxy-D-ribose. The synthesis involves : 1) an aldol like carbon-carbcr. bond formation of (S)-3, 5-dibenzyioxy-2-pentanor.e (8) with a lithium enolate of methyl propanoate, and 2) O-de-benzylation of the aldol adducts (11) for a γ-lactonization followed by β-elimination of the desired butenolide skeleton.