Patent ID: 7071272

Claim:
A method for preparing a compound represented by Formula (2 F ) CR bf R ef =CR df R ef Formula (2 F ) said method comprising: pyrolyzing a compound represented by Formula (1B F ) CXR df R ef —CR bf R cf —COOCF 2 CR bf R cf —CXR df R ef Formula (1B F ) in a gas phase in the presence of a solid catalyst without using a solvent, wherein R bf , R cf , R df , and R ef is independently a fluorine atom or a fluorine-containing monovalent organic group which is not capable of changing during said pyrolyzing; or two of R bf , R cf , R df , and R ef groups are connected with each other to form a fluorine-containing divalent organic group which is not capable of changing during said pyrolyzing, and the two remaining groups are independently a fluorine atom or a fluorine-containing monovalent organic group which is not capable of changing during said pyrolyzing; and X is a halogen atom.