Method of preparing asymmetric phosphate-based compound

A method of preparing an asymmetric phosphate-based compound, comprising synthesizing a compound represented by Chemical Formula 2 below by reacting a cyclic compound represented by Chemical Formula 1 below with a thiolane-based cyclic compound in a hydrophobic solvent under a base-free condition,

• wherein the reaction is performed at −20 to 20° C. under an inert atmosphere
• In Chemical Formulas 1 and 2, R is a substituted or unsubstituted alkylene having 1 to 3 carbon atoms, substitution is independently selected from a halogen, a hydroxyl group, an alkyl group having 1 to 8 carbon atoms, a heteroalkyl group having 3 to 6 carbon atoms, a ketone group, a vinyl group having 1 to 5 carbon atoms, or an aryl group having 6 to 10 carbon atoms, the alkyl group, heteroalkyl group, and aryl group are independently substituted with a halogen, X is chlorine (Cl), bromine (Br), fluorine (F), or iodine (I), n is an integer from 0 to 1, and m is an integer from 1 to 5 (When n is 0, the phosphorus (P) atom has an unshared electron pair instead of oxygen).