Production of 6h-dibenzo(c,e)(1,2)oxaphosphorin-6-one and its derivative

PURPOSE: To industrially advantageously obtain the subject compound usable as an intermediate for flame retarders, or the like, by reacting a specific 6- chloro-(6H)-dibenzo[c,e][1,2]oxaphosphorin with water in a specific condition, and separating and removing the hydrogen chloride gas evolved. CONSTITUTION: A 6H-dibenzo[c,e][1,2]oxaphosphorin-6-one represented by formula II, useful as a production intermediate for a flame retarder and an accelerator in a polymerization process, or the like, or a derivative thereof is obtained with a high yield and a high purity by reacting 6-chloro-(6H)-dibenzo[c, e][1,2]oxaphosphorin represented by formula I, (wherein R 1 and R 2 are each a halogen, a 1-6C alkyl or alkoxy; and (a) and (b) are 0, 1, 2 or 3) with water in a molar ratio of 1:1 at 50 to 250°C optionally in the presence of a solvent such as toluene, or the like, and separating the hydrogen chloride gas involved at the rate of the generation thereof without generating waste water containing hydrochloric acid or an undesired byproduct. COPYRIGHT: (C)1995,JPO