ω-Haloalkylphosphine derivatives undergo the intramolecular nucleophilicsubstitution reaction upon treatment with a strong base, yielding either cycloalkylphosphine derivatives or heterocyclic phosphine derivatives. The selectivity of the cyclization of (ω-haloalkyl)alkylarylphosphine derivatives depends strongly on the distance between the electrophilic and nucleophilic carbon atoms and the structure of the phosphorus