PRODUCTION OF TRANS-DIFLUOROETHYLENE COMPOUND

Japanese Patent JP3777620

B2

PURPOSE: To produce a trans-difluoroethylene compound suitable for a liquid crystal in high yield at a low cost by passing a readily available halogenated cyclohexane compound as a raw material through a lithium compound in three steps. CONSTITUTION: This method for producing a trans-difluoroethylene compound of formula 1 (A2 is trans-1,4-disubstituted cyclohexylene; A1 is A2, etc.; A3 is a 1,4-disubstituted cyclohexenylene, etc.; A4 is A1; Y1 is COO, OCO, C≡C, etc.; Y2 is Y1; (m) is 0 or 1; R1 is an alkyl, etc.; R2 is R1; X is Cl, etc.; (n) is 0 or 1) comprises reacting a halogenated cyclohexane compound of formula 2 with a lithium compound, providing a lithium compound of formula 3, then reacting the resultant compound with trifluoroethylene, affording a compound of formula 4 and further reacting the prepared compound of formula 4 with a lithium compound of formula 6. When an electron-transfer agent is present in the system in the reaction in the first stage, the trans-isomer of the lithium compound of formula 3 is stabler than the cis-isomer thereof. Thereby, the trans-isomer of the compound of formula 1 is a main product. As a result, an inexpensive mixture of the cis- with the trans-isomers can be used as the raw material.