PURPOSE: To obtain the titled compound useful for chemical industry, by reducing an adduct of cyclopentadiene with nitrosyl chloride.

CONSTITUTION: Cyclopentadiene is reacted with nitrosyl chloride to give an adduct of the cyclopentadiene with the nitrosyl chloride expressd by the formula, which is then reduced to afford the aimed compound. The addition reaction is carried out in an organic solvent, e.g. ethyl ether, at -30W+10°C for 2W3hr. The formed adduct expressed by the formula can be isolated easily due to the natural deposition in the case of the reaction carried out in a solvent, e.g. ether. The reduction reaction of the resultant adduct is preferably carried out in a solvent, e.g. ethanol, containing an acid, e.g. acetic acid, due to the high yield obtained under acidic conditions. The reduction can be carried out in the presence of a catalyst, e.g. Raney nickel, by the catalytic reduction method, etc.