Process for preparing 6-oxo-(6H)-dibenz-›C,E! ›1,2!-oxaphosphorins

  • US 5,717,127 A
  • Filed: 04/17/1996
  • Issued: 02/10/1998
  • Est. Priority Date: 04/24/1995
  • Status: Expired due to Fees
First Claim
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1. A process for preparing a 6-oxo-(6H)-dibenz- c,e! 1,2!-oxaphosphorin (ODOP) of the formula ##STR4## where R1 to R6 are identical or different and are hydrogen, halogen, C1 -C4 -alkyl or C1 -C4 -alkoxy,by reaction of an o-phenylphenol of the formula ##STR5## where R1 to R6 are as defined above,with phosphorus trichloride in the presence of a Lewis acid with elimination of hydrogen chloride at elevated temperature in the range from 70°

  • to 220°

    C. in a 1st stage and hydrolysis of the product of the 1st stage in a 2nd stage, wherein, for the purposes of the hydrolysis, ab-chloro-(6H)-dibenz c,e!-oxaphosphorin and water in an at least stoichiometric molar ratio are fed continuously at elevated temperature into a reaction section having very little backmixing, the hydrolysis is carried out continuously along this reaction section at elevated temperature, the reaction products are discharged continuously at the end of the section and ODOP is optionally subjected to further treatment at elevated temperature.

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