The article discusses a study on the chemoselectivity of the reaction of 2-chloro-4(5)-(dichlorophosphoryloxy)-1,3,2-benzodioxaphosphole 2-oxides with phosphorus pentachloride. The study explores the reaction of cyclic chlorophosphates VII and VIII with an equimolar amount of phosphorus pentachloride in methylene chloride. Also tackled is the phosphorus atoms in the resulting 2,2,2-trichloro-4(5)-(dichlorophosphoryloxy)- 1,3,2?5-benzodioxaphospholes.