Patent ID: 8822715

Claim:
A method for producing an aromatic diphosphate comprising: Step 1 in which an aromatic monohydroxy compound having a steric hindrance group at ortho-positions represented by formula (III) wherein R 1 and R 2 each independently is an alkyl group having 1 to 5 carbons; and R 3 is a hydrogen atom or an alkyl group having 1 to 5 carbons, is made to react with phosphorus oxyhalide in the presence of a Lewis acid catalyst and then the unreacted phosphorus oxyhalide is removed under a reduced pressure to give a diaryl phosphorohalidate represented by formula (IV) wherein R 1 , R 2 and R 3 are the same as those in formula (III); and X is a halogen atom; and Step 2 in which the reaction product obtained in Step 1 is made to react with an aromatic dihydroxy compound represented by formula (V) in an amount of 0.5 mol with respect to 1 mol of halogen contained in the reaction product wherein R 4 is a hydrogen atom or an alkyl group having 1 to 5 carbons; Y is a bonding arm or a —CH 2 —, —C(CH 3 ) 2 —, —S—, —SO 2 —, —O—, —CO— or —N═N— group; k is 0 or 1; and m is an integer of 0 to 4, in the presence of a Lewis acid catalyst to give an aromatic diphosphate represented by formula (I) wherein R 1 , R 2 and R 3 are the same as those in formula (III); and R 4 , Y, k and m are the same as those in formula (V).