To obtain the endo isomer of an alkyl-substituted cyclopentadiene compound in a high yield by adding an acidic slurrying agent-containing aqueous solution to the reaction mixture of an alkylcyclopentenone compound with an alkyl Grignard reagent and adding an acid catalyst to the obtained slurry liquid to remove the water.
This method for producing an alkyl-substituted cyclopentadiene compound of formula IV (for example, 1-methyl-3-butylcyclopentane-1,3-diene) comprises subjecting (A) a compound of formula I [R1 is a 1-4C alkyl; (m) is 1-3] (for example, 3-methyl-2-cyclopentenone) and (B) a compound of the formula: R2CH2MgX (R2 is a 1-7C alkyl; X is a halogen) (for example, ethyl magnesium chloride) to an alkylation reaction, mixing the obtained reaction mixture containing the compound of formula II with (C) an acidic slurrying agent (for example, orthphosphoric acid)-containing aqueous solution to form a slurry liquid, and then adding an acid catalyst (for example, hydrochloric acid) to the slurry liquid to remove the OH group from the compound of formula III in the slurry liquid, thus obtaining the compound of formula III.
YOSHIKAWA AKIRA
ISODA YOICHIRO
