The invention relates to a process for the halogenation of cyclopropylmethyl ketone with at least one dihalo-triorganophosphorane of the general formula I R3PHal2   (I), in which the radicals R can be the same or different and denote a saturated or unsaturated aliphatic C1-C20 hydrocarbon radical, a phenyl or (C1-C4 alkyl)phenyl radical, which may be optionally substituted by one or two fluorine, chlorine and/or nitro groups, P stands for phosphorus and Hal denotes chlorine, bromine, or iodine, at a temperature of from 800° to 130° C., where the dihalo-triorganophosphane of the general formula (I) is synthesized in situ from triorganophosphane oxide or triorganophosphane sulfide of the general formula II R3PA   (II), in which R is as defined above with respect to formula I and A denotes oxygen or sulfur, using a halogenating agent, wherein the triorganophosphane oxide or triorganophosphane sulfide is used in catalytic amounts, to the halogenation product of cyclopropylmethyl ketone obtained in said process, and to a process for the conversion of said halogenation product to cyclopropylacetytene.