Method for the production of 4,4′-[1-(trifluoromethyl)alkylidene]-bis-(2,6-diphenylphenols)

Abstract

The present invention relates to a process for preparing 4,4′-[1-(trifluoromethyl)alkylidene]bis(2,6-diphenylphenols), in particular for preparing 4,4′-[1-(trifluoromethyl)ethylidene]bis(2,6-diphenylphenol), which comprises the self-condensation of cyclohexanone in the presence of a basic catalyst to form tricyclic condensation products, dehydrogenation of the resulting tricyclic condensation products in the presence of a supported transition metal catalyst in the condensed phase to form 2,6-diphenylphenol and reaction of the 2,6-diphenylphenol with a trifluoromethyl ketone. The invention further provides an improved process for preparing 2,6-diphenylphenol by aldol self-condensation of cyclohexanone.

The invention claimed is: 
     
       1. A process for preparing 4,4′-[1-(trifluoromethyl)alkylidene]bis(2,6-diphenylphenols) of the formula (I) 
       
         
           
           
               
               
           
         
       
       where the radical
 R is unbranched or branched C 1 -C 6 -alkyl or C 1 -C 6 -perfluoroalkyl, 
 
       which comprises the process steps
 a) reaction of cyclohexanone in the presence of a basic catalyst to form a reaction mixture comprising the tricyclic condensation products of the formula (IIa), (IIb) and/or (IIc) 
 
       
         
           
           
               
               
           
         
       
       and water,
 b) separation of a mixture of the tricyclic condensation products comprising the compounds of the formulae (IIa), (IIb) and/or (IIc) from the reaction mixture formed in step a), 
 c) dehydrogenation of the tricyclic condensation products comprising the compounds of the formulae (IIa), (IIb) and/or (IIc) obtained in step b) in the presence of a Al 2 O 3  supported transition metal Pd catalyst, and carbonates of alkali metals or alkaline earth metals, in the condensed phase to form a reaction mixture comprising 2,6-diphenylphenol of the formula (III), 
 
       
         
           
           
               
               
           
         
         d) separation of 2,6-diphenylphenol of the formula (III) from the reaction mixture formed in step c) and 
         e) reaction of the 2,6-diphenylphenol of the formula (III) obtained in step d) with a trifluoromethyl ketone of the formula (IV) 
       
       
         
           
           
               
               
           
         
       
       where the radical R is as defined for formula (I), in the presence of a strong organic acid to form the 4,4′-[1-(trifluoromethyl)alkylidene]bis(2,6-diphenylphenol) of the formula (I). 
     
     
       2. The process of  claim 1 , wherein an aqueous solution of an alkali metal hydroxide or alkaline earth metal hydroxide is used as basic catalyst in step a). 
     
     
       3. The process of  claim 1 , wherein an aqueous solution of sodium hydroxide is used as basic catalyst in step a). 
     
     
       4. The process of  claim 1 , wherein the reaction according to step a) is carried out at a temperature in the range from 90 to 180° C. 
     
     
       5. The process of  claim 1 , wherein the reaction according to process step a) is carried out in the presence of a solvent or solvent mixture which forms an azeotrope with water. 
     
     
       6. The process of  claim 5 , wherein the water formed in step a) is separated from the reaction mixture by distillation in the form of an azeotrope with the solvent or solvent mixture used during the reaction. 
     
     
       7. The process of  claim 5 , wherein xylene, toluene or ethylbenzene or a mixture thereof is used as solvent. 
     
     
       8. The process of  claim 1 , wherein the separation according to process step b) is carried out in the form of a distillation. 
     
     
       9. The process of  claim 1 , wherein the dehydrogenation according to process step c) is carried out in the presence of a catalyst comprising palladium and/or platinum on a support. 
     
     
       10. The process of  claim 1 , wherein the dehydrogenation according to process step c) is carried out in the presence of a Pd catalyst supported on Al 2 O 3  or a carbon support. 
     
     
       11. The process of  claim 1 , wherein the dehydrogenation according to process step c) is carried out in the presence of hydroxides or carbonates of alkali metals or alkaline earth metals. 
     
     
       12. The process of  claim 1 , wherein the isolation of 2,6-diphenylphenol according to process step d) is carried out in the form of a crystallization. 
     
     
       13. The process of  claim 1 , wherein the reaction according to process step e) is carried out at a temperature in the range from 10 to 60° C. 
     
     
       14. The process of  claim 1 , wherein the reaction according to process step e) is carried out in the presence of an organic acid having a pKa of up to 2. 
     
     
       15. The process of  claim 1 , wherein the reaction according to process step e) is carried out in the presence of methanesulfonic acid. 
     
     
       16. The process of  claim 1 , wherein 2,6-diphenylphenol and the trifluoromethyl ketone of the formula (IV) are used in a molar ratio of from 1:1 to 2:1 in process step e). 
     
     
       17. The process of  claim 1 , wherein the radical R is methyl or trifluoromethyl. 
     
     
       18. The process of  claim 1 , wherein the radical R is methyl. 
     
     
       19. The process of  claim 1 , wherein the 4,4′-[1-(trifluoromethyl)alkylidene]bis(2,6-diphenylphenol) of the formula (I) formed in process step e) is separated off from the resulting reaction mixture by extraction. 
     
     
       20. A process for preparing 2,6-diphenylphenol of the formula (III) 
       
         
           
           
               
               
           
         
       
       which comprises the steps
 i) reaction of cyclohexanone in the presence of a basic catalyst to form a reaction mixture comprising the tricyclic condensation products of the formula (IIa), (IIb) and/or (IIc) 
 
       
         
           
           
               
               
           
         
       
       and water in the presence of a solvent or solvent mixture other than cyclohexanone which forms an azeotrope with water, with the water formed being separated off from the reaction mixture by distillation in the form of an azeotrope with the solvent or solvent mixture used during the reaction,
 ii) separation of a mixture of the tricyclic condensation products of the formulae (IIa), (IIb) and/or (IIc) from the reaction mixture formed in step i) and 
 iii) dehydrogenation of the tricyclic condensation products comprising the compounds of the formulae (IIa), (IIb) and/or (IIc) obtained in step ii) in the presence of a Al 2 O 3  supported transition metal Pd catalyst, and carbonates of alkali metals or alkaline earth metals, in the condensed phase to form a reaction mixture comprising 2,6-diphenylphenol of the formula (III) 
 
       
         
           
           
               
               
           
         
       
     
     
       21. A process for dehydrogenating compounds of formula (IIa), (IIb), and/or (IIc) 
       
         
           
           
               
               
           
         
       
       in the presence of an Al 2 O 3  supported Pd catalyst, and carbonates of alkali metals, in the condensed phase to form a reaction mixture comprising 2,6-diphenylphenol of formula (III), 
       
         
           
           
               
               
           
         
       
       
        
       
     
     
       22. The process of claim 21, further comprising separating the supported Pd catalyst from the reaction mixture and reuse the catalyst for at least four times in subsequent dehydrogenation processes of compounds of formula (IIa), (IIb), and/or (IIc) without appreciable decreases in activity or selectivity. 
     
     
       23. The process of claim 1, further comprising separating the supported Pd catalyst from the reaction mixture and reuse the catalyst for at least four times in subsequent dehydrogenation processes of compounds of formula (IIa), (IIb), and/or (IIc) without appreciable decreases in activity or selectivity. 
     
     
       24. The process of claim 20, further comprising separating the supported Pd catalyst from the reaction mixture and reuse the catalyst for at least four times in subsequent dehydrogenation processes of compounds of formula (IIa), (IIb), and/or (IIc) without appreciable decreases in activity or selectivity.