Method for producing unsaturated acid ester or unsaturated acid

A method for producing an unsaturated-acid ester or an unsaturated acid, comprising a step of reacting a compound (1) represented by the following formula (1) with a compound (2) represented by the following formula (2) (excluding the compound (1)) in the presence of a Lewis acid catalyst at a temperature of the boiling point of the compound (1) or higher and 350° C. or lower, thereby obtaining products including a compound (3) represented by the following formula (3):

• (in formula (1), R1, R2 and R4 each independently are a hydrogen atom, a deuterium atom, or an alkyl group which has a carbon number of from 1 to 3 and may have been substituted with a halogen atom and/or a deuterium atom, R3 and R5 each independently are a hydrogen atom or a deuterium atom, and X is a chlorine atom, a fluorine atom, a bromine atom, or an iodine atom);
• R6—OR7 (2)
• (in formula (2), R6 is a hydrogen atom, a deuterium atom, an alkyl group which has a carbon number of from 1 to 11 and may have been substituted with a halogen atom and/or a deuterium atom, or an aryl group which has a carbon number of from 1 to 11 and may have been substituted with a halogen atom and/or a deuterium atom, and R7 is a hydrogen atom or a deuterium atom);
• and
• (in formula (3), R1, R2 and R4 are the same as defined above with regard to formula (1), and R6 is the same as defined above with regard to formula (2)).