Methylidene malonate process

Abstract

An improved process for the production of methylidene malonates is attained by use of select iminium salt reactants.

We claim: 
     
         1 . A method of producing methylidene malonates by reacting esters, especially diesters, of malonic acid with certain iminium salts under appropriate conditions and for an appropriate time period to yield the corresponding methylidene malonate wherein the iminium salts generally correspond to the formula 
       
         
           
           
               
               
           
         
       
       wherein R 4 , R 5 , R 6  and R 7  are each independently H or a hydrocarbon or substituted hydrocarbon moiety or a hydrocarbon, substituted hydrocarbon or heterohydrocarbon bridge whereby the nitrogen atom, the carbon, or both of formula H are in a ring structure; provided that neither of R 6  and R 7  is a hydrocarbon moiety comprising a tertiary carbon attached to the N atom and X is an anion. 
     
     
         2 . The method of  claim 1  wherein R 4 , R 5 , R 6  and R 7  are each independently H or an alkyl, aryl, alkenyl or alkynyl. 
     
     
         3 . The method of  claim 1  wherein X is a halogen, a non-nucleophilic anion, and/or acidic anion. 
     
     
         4 . The method of  claim 1  wherein X is a halogen, a carboxylate or a sulfonate. 
     
     
         5 . The method of  claim 1  wherein X is selected from chloride, bromide, iodide, AsF 6 , SbF 6 , PF 6 , BF 4 , CH 3 SO 3 , CF 3 SO 3 , benzenesulfonate, para-toluenesulfonate, acetate, propionate, isobutyrate, pivalate, sufate, bisulfate, perchlorate, SbCl 6 , SbCl 3 , and SnCl 5    
     
     
         6 . The method of  claim 1  wherein the maloriic acid ester has the formula 
       
         
           
           
               
               
           
         
       
       wherein, in the case of the mono-esters, one of R 1  and R 2  is H and the other a C 1  to C 18  hydrocarbon or heterohydrocarbon group, the latter having one or more nitrogen, halogen, or oxygen atoms or, in the case of the diester, both R 1  and R 2 , which may be the same or different, are each independently selected from C 1  to C 18  hydrocarbon or heterohydrocarbon groups, the latter having one or more nitrogen, halogen, or oxygen atoms. 
     
     
         7 . The method of  claim 6  wherein R 1  and R 2  are both hydrocarbon and/or heterohydrocarbon groups and represent a C 1  to C 10  linear or branched alkyl group, a C 3  to C 6  alicyclic group, a C 2  to C 6  alkenyl group, or a C 2  to C 6  alkynyl group, either or both of which may be substituted with or contain an ether, epoxide, halo, ester, cyano, aldehyde, keto or aryl group. 
     
     
         8 . The method of  claim 6  wherein both R 1  and R 2  are hydrocarbon or heterohydrocarbon groups wherein at least one contains an ester linkage. 
     
     
         9 . The method of  claim 6  wherein wherein at least one of the R 1  and R 2  groups is of the formula:
   —(CH 2 ) n —COOR 3  
 
 
       wherein R 3  is a C 1  to C 17  hydrocarbon or heterohydrocarbon group, the latter having one or more nitrogen, halogen, or oxygen atoms 
     
     
         10 . The method of  claim 6  wherein the malonic acid ester is a diester and a least one of R 1  and R 2  is a group is of the formula:
   —(CH 2 ) n —COOR 3  
 
 
       wherein R 3  is independently a C 1  to C 17  hydrocarbon or heterohydrocarbon group, the latter having one or more nitrogen, halogen, or oxygen atoms, and n is an integer of from 1 to 5. 
     
     
         11 . The method of  claim 10  wherein R 3  is independently a C 1  to C 6  lower alkyl and n is 1 or 2. 
     
     
         12 . The method of  claim 1  wherein the equivalent weight of iminium salt to malonic acid ester is from 1:1 to 10:1. 
     
     
         13 . The method of  claim 1  wherein the equivalent weight of iminium salt to malonic acid ester is from 1:1 to 6:1. 
     
     
         14 . The method of  claim 1  wherein the equivalent weight of iminium salt to malonic acid ester is from 1:1 to 4:1. 
     
     
         15 . The method of  claim 1  wherein the iminium salt is formed in-situ and the malonic acid ester is directly added to the iminium reaction product. 
     
     
         16 . The method of  claim 15  wherein the in-situ reaction involves an excess molar equivalent of the anhydride or acid chloride activation agent. 
     
     
         17 . The method of  claim 15  wherein the iminim salt is formed by the reaction of an acid halide or an acid anhydride with a 1,1-diaminoalkane. 
     
     
         18 . The method of  claim 1  wherein the reaction is performed in the presence of a polar solvent. 
     
     
         19 . The method of  claim 1  wherein the reaction is performed in the presence of a non-polar solvent and the anion of the iminium salt is a carboxylate. 
     
     
         20 . A method of producing methylidene malonates comprising the steps of forming an iminium salt generally correspond to the formula 
       
         
           
           
               
               
           
         
       
       wherein R 4 , R 5 , R 6  and R 7  are each independently H or a hydrocarbon or substituted hydrocarbon moiety or a hydrocarbon, substituted hydrocarbon or heterohydrocarbon bridge whereby the nitrogen atom, the carbon, or both of formula II are in a ring structure; provided that neither of R 6  and R 7  is a hydrocarbon moiety comprising a tertiary carbon attached to the N atom and X is an anion, and
 allowing the so formed iminium salt to react with a malonic acid ester under appropriate conditions and for an appropriate time period to yield the corresponding methylidene malonate.