Due to the high strain energy spiranes containing small cycles are interesting objects for phosphorylation with phosphorus compounds of various coordination. It is known that one of the available mild phosphorylating agents is phosphorus pentachloride possessing electrophilic character [1]. Therefore, its reaction with such spiranes may occur through an opening of a three-or four-membered rings to produce new types of phosphorylated cyclic hydrocarbons.We showed that the interaction of spiro[2.2]pentane I with phosphorus pentachloride under standard conditions [2] (benzene, 0-20°C, quenching reagent acetone) resulted in 1-chlorocyclobutyl-methylphosphonic acid dichloride II.