Method for the preparation of biphosphites

A process for preparing bisphosphites of the formula I

• wherein R1, R2, R3, R4 are independently selected from H, aliphatic, alicyclic, aliphatic-alicyclic, heterocyclic, aliphatic-heterocyclic, aromatic, aromatic-aromatic, aliphatic-aromatic hydrocarbon radical having from 1 to 50 carbon atoms, F, Cl, Br, I, —CF3, —OR7, —COR7, —CO2R7, —CO2M, —SR7, —SO2R7, —SOR7, —SO3R7, —SO3M, —SO2NR7R8, NR7R8, N═CR7R8, or NH2, wherein R1 to R4 may be covalently linked to one another,
• R7, R8 are independently selected from H or a substituted or unsubstituted, aliphatic or aromatic hydrocarbon radical having from 1 to 25 carbon atoms, atoms,
• M is an alkali metal ion, alkaline earth metal ion, ammonium ion, or phosphonium ion,
• Q is a divalent aliphatic, alicyclic, aliphatic-alicyclic, heterocyclic, aliphatic-heterocyclic, aromatic, or aliphatic-aromatic hydrocarbon radical having from 1 to 50 carbon atoms,
• Z, Y are each Cl, Br, or I,
• W, X are independently selected from an aliphatic, alicyclic, aliphatic-alicyclic, heterocyclic, aliphatic-heterocyclic, aromatic, aromatic-aromatic, or aliphatic-aromatic hydrocarbon radical having from 1 to 50 carbon atoms and may be covalently linked to one another,
• the process comprising carrying out the reaction sequence
• wherein the reaction steps a), b) and c) are carried out in aprotic and nonpolar solvents,
• the adduct base•HY or base•HZ is filtered off after at least one of the reaction steps a), b) and c) and
• the end product is isolated and purified.