Dietmar Bielefeldt

Synthese von α-Fluoracrylsäure und Derivaten

Zusammenfassung Three new routes to derivatives of α-fluoracrylic acid, including a laboratory synthesisand a large-scale method, are reported. The processes are (i) addition of elementaryfluorine to acrylic esters and subsequent elimination of HF; (ii) addition of difluorocarbeneto isopropenyl methyl ether, oxidation via ring opening and dehalogenation; and (iii)‘nitrofluorination’ of 2,3-dichloropropene, hydrolysis and dechlorination.

1,1,1,4,4,4-Hexafluorbutane (R 356), a potential CFC substitute

Abstract As part of the world-wide efforts to limit the antropogenic depletion of the stratospheric ozone layer, there is an intensive search for substitutes for all chlorine-containing compounds used in refrigeration. Beside the H-CFCs with reduced ozone depletion potential (ODP), to date only perfluoroalkanes with a high greenhouse potential have been put forward as blowing agents in PUR rigid foams. We consider 1,1,1,4,4,4-hexafluorbutane (R 356) to be the better alternative than the above-mentioned substitutes. In spite of the C4-carbon framework, the physical properties of hexafluorbutane are very similiar to those of R 11. R 356 is not combustible, nor is a gas-air-mixture explosive. Hexafluorbutane also seems to be well-suited from the ecological point of view: by definition, its ozone depletion potential is zero. Due to the partial hydrocarbon character, R 356 is rapidly decomposed in the atmosphere, and thus contributes only minimally to the greenhouse effect. A synthetic route is presented, and an overview given of properties of the technical application of R 356 in PUR rigid foam.

Synthesis of fluorinated sulfanes and the new 1,1-difluoroethylsulfenyl chloride

Abstract The addition reactions of thiophenol and benzylmercaptan to terminal difluoroethylenes under radical conditions as well as under basic conditions are investigated. A new synthesis of 1,1-difluoroethylsulfenyl chloride, which comprises the base-catalyzed addition of benzylmercaptan to vinylidene fluoride and subsequent chlorolysis, is described: PhCH 2 SH+CF 2 CH 2 →PhCH 2 SCF 2 CH 3 PhCH 2 SCF 2 CH 3 CH 3 CF 2 SCl Examples of the syntheses of active compounds using 1,1-difluoroethylsulfenylchloride are given.

New approaches to α-fluoroacrylic acid

Abstract Three new routes to derivatives of α-fluoracrylic acid including a laboratory synthesis and a large scale method are presented which comprises of i) addition of elementary fluorine to acrylic esters and subsequent elemination of HF, ii) addition of difluorocarbene to isopropenyl methyl ether, oxidation via ring opening and dehalogenation, and iii) ‘nitrofluorination’ of 2,3-dichloropropene, hydrolysis and dechlorination.