Process for producing indenol esters or ethers

Abstract

The present invention relates to a process for making indenol esters or ether from an α-substituted cinnamic aldehyde derivative such as an acetal or an acylal. This reaction is promoted by the use of strong mineral acids, sulphonic acids, acidic zeolites or Lewis acids.

1 . A process for making a compound of formula  
     
       
         
         
             
             
         
       
       wherein m is 0, 1 or 2;  
       R 1  represents a formyl group, a —COCOOH group or a group of formula —(CO) n —R-T, in which n is 0 or 1, R is a C 6 H 4  group, C 1-5  alkanediyl or alkenediyl group and T is OH, COOH or a hydrogen atom;  
       R 2  represents a C 1-6  alkyl or alkenyl group;  
       at least one R 3  represents a hydrogen atom and the other R 3  represent each a hydrogen atom or a C 1-5  alkyl, alkenyl or alkoxy group; and  
       R 4  represents a hydrogen atom, a phenyl group or a R 2  group;  
       comprising the cyclization, at a temperature above 10° C., of the corresponding compound of formula  
       
         
           
           
               
               
           
         
       
       wherein each R 5 , taken separately, represents a formyl group or a —(CO) n —R—H group, or the R 5 , taken together, represent a —(CO) n —R—(CO) n — group or a —COCO— group;  
       the wavy line indicates that the configuration of the carbon-carbon double bond is E or Z or a mixture thereof; and  
       m, n, R, R 2 , R 3  and R 4  have the meaning as indicated above;  
       in the presence of a catalyst selected from the group consisting of strong mineral protic acids, sulphonic acids, acidic zeolites and Lewis acids.  
     
   
   
       2 . A process according to  claim 1 , wherein m is 0 or 1.  
   
   
       3 . A process according to  claim 1 , wherein the compounds of formula (I) are of formula  
     
       
         
         
             
             
         
       
     
     and are obtained by cyclization of the corresponding compounds of formula  
     
       
         
         
             
             
         
       
     
     wherein R 1 , R 2 , R 3  and R 5  have the same meaning as in  claim 1 .  
   
   
       4 . A process according to  claim 1 , wherein the catalyst is selected from the group consisting of H 2 SO 4 , p-toluenesulphonic acid, NaHSO 4 , KHSO 4 , H 3 PO 4 , HCl, HNO 3 , and BF 3 , and its adducts with C 2-6  ethers or with C 2-6  carboxylic acids, poly(styrene sulphonic acid) based resins, K-10 Clay, SnX 4 , FeX 3  and ZnX 2 , X representing a halogen atom, a C 1-6  carboxylate, or a C 1-7  sulphonate.  
   
   
       5 . A process according to  claim 4 , wherein the catalyst is H 3 PO 4 , FeX 3  or ZnX 2 , X having the same meaning as in  claim 4 .  
   
   
       6 . A process according to  claim 1 , characterized in that it further comprises the step of generating in situ the compound of formula (II) starting from the corresponding enal of formula  
     
       
         
         
             
             
         
       
     
     wherein R 2 , R 3 , R 4  and R 5  have the same meaning as indicated in  claim 1 .  
   
   
       7 . A process according to  claim 6 , wherein the compound of formula (II) is an acetal or an acylal.  
   
   
       8 . A compound of formula  
     
       
         
         
             
             
         
       
       wherein one R 3  is a hydrogen atom and the other R 3  is a C 1-5  alkyl group, which n is 0 or 1, R is a C 6 H 4  group, C 1-5  alkanediyl or alkenediyl group and T is OH, COOH or a hydrogen atom; and  
       R 2  represents a C 1-6  alkyl or alkenyl group.  
     
   
   
       9 . A compound according to  claim 8 , wherein the compound is the 2-methyl, the 2,5-dimethyl or the 2,6-dimethyl derivative of compound of formula I.