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A novel, metal-free aerobic oxidation method is described. 4-Dimethylaminopyridine (DMAP) successfully catalyzed the oxidation of aryl α-halo esters to corresponding aryl α-keto esters (up to 95% yield) under mild reaction conditions (Li 2 CO 3 , dimethylacetamide, air, and room temperature). A mechanism has been proposed where the oxidation proceeds through a [3 + 2] cycloaddition between O 2 in an air atmosphere and pyridinium ylides. The ylides are supposedly generated from aryl α-halo esters and DMAP in the presence of carbonates. Based on the plausible mechanism, the potential of DMAP as a catalyst in oxidation reactions was extended.

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Thermoreversible gelation of poly(vinylidene fluoride) (PVDF) in propylene carbonate (PC) solutions at relatively low concentrations (0.5-3.5 wt.%) has been studied in terms of the gelation time (or rate) as a function of temperature and polymer concentration. A master curve could be made for the gelation time -temperature curves using the temperature shift based on the difference in the gel melting temperature (T m g ) at different PVDF concentrations. The apparent activation energy of gelation was estimated to be proportional to (T m g 2 T) 21.8 . The gel melting enthalpy (DH m g ) determined from the modified Eldrige -Ferry equation was 18.67 kJ/mol. In dried gel films many spherulites connected by tie molecules were observed by scanning electron microscopy (SEM). From the wide angle x-ray diffraction (WAXD) measurement, crystallites from PVDF gels were found to consist only of the g-type crystal with the TTTGTTTḠ conformation, irrespective of the polymer concentration. As judged from the results 741 ORDER REPRINTS obtained, the gelation of PVDF in PC seems to proceed mainly via liquid-liquid phase separation (even if followed by crystallization in the final stage) within the concentration range covered.