Total Synthesis of Gelsedilam by Means of a Thiol-Mediated Diastereoselective Conjugate Addition-Aldol Reaction.

The total synthesis of gelsedilam, which features a highly diastereoselective thiol conjugate addition-intramolecular aldol reaction to install the strained and caged [3.2.2] bridged ring system and highly efficient NiCl2 /NaBH4 -mediated four-step transformation in one-pot to construct its five-membered lactam ring is reported. The synthesis requires only 18 linear steps from the known compounds, providing useful strategies for the construction of the intricate ring system in the synthesis of related gelsedine-type alkaloids.

Enantioselective direct Mannich reactions of cyclic ß-ketoesters catalyzed by chiral phosphine via a novel dual-reagent catalysis.

A combination of an amino acid derived chiral phosphine catalyst and methyl acrylate efficiently catalyzed the direct Mannich reaction of cyclic ß-ketoesters and N-Boc-aldimines. The dual-reagent catalysis was presumed to function through the formation of a zwitterion, which catalyzed the reaction with excellent stereocontrol via a hydrogen-bonding assisted chiral ion-pair pathway.

[Study on thermal decompositon properties of hexafluoropropane clean gaseous fire-extinguishing agent].

The thermal decomposition properties of hexafluoropropane clean gaseous fire-extinguishing agent were studied in tubular reactor from 500 to 750 degrees C and the decomposed gas was characterized by gas chromatography(GC), Fourier transform infrared spectroscopy (FTIR) and gas chromatography-mass spectrometry (GC-MS). Hydrogen fluoride was detected after the decomposed gas was analyzed by pH testing, while pentafluoropropylene was found by GC-MS. The results showed that hydrogen fluoride eliminated from hexafluoropropane was the main reaction, while pentafluoropropylene was the primary product during hexafluoropropane decomposition under high temperature. GC and FTIR results indicated that the reaction temperatures had significant effects on the thermal decomposition of hexafluoropropane. Haxafluropropane was steady at 500 degrees C, whereas started to decompose weakly at 600 degrees C. The degree of the thermal decomposition of hexafluoropropane was enhanced with the temperature increase. And hexafluoropropane underwent intense decompositon at 750 degrees C. FTIR can be used as a new method to study extinguishing mechanism of fluorine-containing fire extinguishing agent online.