To obtain 4-vinylcylohexene, etc., useful as a chemical raw material, etc., in a high selectivity and in a high yield by cyclically dimerizing a conjugated diolefin in the presence of a specific stable and highly active catalyst easy in treatment.
This method for cyclically dimerizing a conjugated diolefin such as 1,3-butadiene, isoprene or norbornadiene comprises cyclically dimerizing the conjugated diolefin in the presence of a catalyst comprising a tricarbonyl nitrosyl iron acid onium salt of the formula (A+ is an onium ion) as a catalyst precursor and a strong protonic acid, such as trifluoroacetic acid or methane sulfonic acid, having an acid dissociation index of ≤0.5 in water at 25°C (preferably in an amount of 0.1-2 moles based on the tricarbonyl nitrosyl iron acid onium salt) in a solvent such as benzene.
SHIRASAKI YOSHIKAZU
OKAGO YUJI
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