Processes for producing Z-1,1,1,4,4,4-hexafluorobut-2-ene and intermediates for producing same

A process to produce Z-1,1,1,4,4,4-hexafluoro-2-butene comprising:

• (a′) contacting trichloroethylene in the presence of a dimerization catalyst to produce a product mixture comprising 1,1,2,4,4-pentachlorobuta-1,3-diene (HCC-2320az), wherein the dimerization catalyst comprises iron or copper;
• (a) contacting 1,1,2,4,4-pentachlorobuta-1,3-diene produced in step (a′) with hydrogen fluoride in the liquid phase in the presence of a fluorination catalyst to produce a product mixture comprising 2-chloro-1,1,1,4,4,4-hexafluorobutane (HCFC-346mdf);
• (b) contacting 2-chloro-1,1,1,4,4,4-hexafluorobutane with base to produce a product mixture comprising E-1,1,1,4,4,4-hexafluoro-2-butene (E-1336mzz);
• (c) contacting E-1, 1,1,4,4,4-hexafluoro-2-butene with a chlorine source in the presence of a catalyst to produce a product mixture comprising 2,3-dichloro-1,1,1,4,4,4-hexafluorobutane (HCFC-336mdd);
• (d) contacting 2,3-dichloro-1,1,1,4,4,4-hexafluorobutane with a base to produce a product mixture comprising 1,1,1,4,4,4-hexafluoro-2-butyne;
• and (e) contacting 1,1,1,4,4,4-hexafluoro-2-butyne with hydrogen to produce a product mixture comprising Z-1,1,1,4,4,4-hexafluoro-2-butene, wherein step (a′) is performed in the presence of pentachloroethane, wherein the weight ratio of pentachlororethane to trichloroethylene is from about 0.001 to about 1.