The present invention relates to a synthesis of an 8-membered carbocyclic compound having diexomethylene groups, more particularly to a synthesis of an 8-membered carbocyclic compound having diexomethylene groups, a novel compound having the structure represented by the following Chemical Formula 1, from trimethylsilanylmethyl-allenol derivative by the intramolecular Prins cyclization using Lewis acid. The 8-membered carbocyclic compound is a useful intermediate for synthesis of other multicarbocyclic compounds. In Chemical Formula 1, R1 is a phenyl group, and R2 and R3 is a hydrogen atom, or R1, R2 and R3 may be connected with neighboring substituents to form a 5 to 10-membered aliphatic or aromatic ring.