Method for preparing a biphenylphosphonate compound

A method for preparing a biphenylphosphonate compound of the following formula (I): wherein n is 2 or 3; Ar is a C6-C16 aromatic group; which comprising (a) reacting an o-phenylphenol with a phosphorus trichloride in the presence of a zinc chloride catalyst to form a 6-chloro-6H-dibenz [c,e][1,2] oxaphosphorin of the following formula (II); (b) reacting a polyhydroxybenzene compound of the formula (III) (HO)n-Ar (III) wherein n and Ar are defined the same as the above, with the compound of formula (II) to form a compound of the following formula (IV) wherein n and Ar are defined the same as the above; and (c) oxidizing the compound of formula (IV) in the presence of water and ozone to form the compound of formula (I).