Highly active multidentate catalysts for efficient alkyne metathesis

Abstract

The invention relates to highly active and selective catalysts for alkyne metathesis. In one aspect, the invention includes a multidentate organic ligand wherein one substrate-binding site of the metal center is blocked. In another aspect, the invention includes N-quaternized or silane-based multidentate organic ligands, capable of binding to metals. In yet another aspect, the invention includes N-quaternized or silane-based multidentate catalysts. The catalysts of the invention show high robustness, strong resistance to small alkyne polymerization and significantly enhanced catalytic activity compared to their corresponding non-quaternized or non-silane-based multidentate catalyst analogues.

1 . A compound of formula (I), or a salt thereof: 
       
         
           
           
               
               
           
         
       
       wherein
 each G is independently alkyl, aryl or heteroaryl, wherein the alkyl, aryl or heteroaryl is optionally and independently substituted with at least one alkyl, halogen or electron-withdrawing substituent; 
 R 4  is a single bond, heteroatom, or an optionally substituted C 1 -C 3  alkyl; and, 
 R 1  is selected from the group consisting of N, N + H(A − ), and P, and A −  is an anion. 
 
     
     
         2 . The compound of  claim 1 , wherein R 1  is N and each G is independently substituted with at least one electron-withdrawing substituent. 
     
     
         3 . (canceled) 
     
     
         4 . The compound of  claim 1 , wherein the compound of formula (I) is the compound of formula (II) or a salt thereof: 
       
         
           
           
               
               
           
         
       
       wherein:
 R 1  is selected from the group consisting of N, N + H(A − ), and P, and A −  is an anion; 
 each occurrence of n is independently 0, 1, 2, 3 or 4; 
 each occurrence of R 2  is independently alkyl, halogen or an electron-withdrawing group; 
 
       with the proviso that, if R 1  is selected from the group consisting of N and P, at least one occurrence of n is not zero, and at least one occurrence of R 2  is an electron-withdrawing group. 
     
     
         5 . (canceled) 
     
     
         6 . The compound of  claim 4 , wherein the compound of formula (II) is 
       
         
           
           
               
               
           
         
       
     
     
         7 . A compound of formula (III) or a salt thereof: 
       
         
           
           
               
               
           
         
       
       wherein:
 each G is independently alkyl, aryl or heteroaryl, wherein the alkyl, aryl or heteroaryl is optionally and independently substituted with alkyl, halogen or electron-withdrawing substituents; 
 R 1  is selected from the group consisting of N, N + (A − ), and P, and A −  is an anion; 
 R 3  is selected from the group consisting of alkyl, alkyl(aryl) and aryl, all of which are optionally substituted; 
 R 4  is a single bond, heteroatom, or an optionally substituted C 1 -C 3  alkyl chain; and, 
 M is a metal. 
 
     
     
         8 . The compound of  claim 7 , wherein M is a transition metal. 
     
     
         9 . The compound of  claim 8 , wherein M is selected from the group consisting of Mo, W, Re and Ta. 
     
     
         10 . The compound of  claim 7 , wherein R 1  is N and each G is independently substituted with at least one electron-withdrawing substituent. 
     
     
         11 . (canceled) 
     
     
         12 . The compound of  claim 7 , wherein G is phenyl, naphthyl or anthracenyl. 
     
     
         13 . The compound of  claim 7 , wherein the compound of formula (III) is the compound of formula (IV) or a salt thereof: 
       
         
           
           
               
               
           
         
       
       wherein:
 each occurrence of n is independently 0, 1, 2, 3, or 4; 
 R 1  is selected from the group consisting of N, N + H(A − ), and P, C and A −  is an anion; 
 each occurrence of R 2  is independently selected from the group consisting of alkyl, alkoxy, halogen, nitro, cyano, trifluoromethyl, trichloromethyl, carboxy, formyl, lower alkanoyl, carboxyamido and aryl lower alkanoyl; 
 R 3  is alkyl, alkyl(aryl) or aryl, all of which are optionally substituted; and 
 M is selected from the group consisting of Mo, W. Re and Ta, 
 
       with the proviso that, if R 1  is selected from the group consisting of N and P, at least one occurrence of n is not zero. 
     
     
         14 . The compound of  claim 13 , wherein R 1  is N + H(A − ), and A −  is an anion. 
     
     
         15 . The compound of  claim 13 , wherein the compound of formula (III) is selected from the group consisting of: 
       
         
           
           
               
               
           
         
       
     
     
         16 . (canceled) 
     
     
         17 . A method of preparing an alkyne-containing metathesis product, the method comprising contacting a first alkyne-containing substrate with a second alkyne-containing substrate in the presence of a compound of formula (IV) or a salt thereof, whereby the metathesis product of the first and second alkyne-containing substrates is formed: 
       
         
           
           
               
               
           
         
       
       wherein:
 each occurrence of n is independently 0, 1, 2, 3, or 4; 
 R 1  is selected from the group consisting of N, N + H(A − ), and P, C and A −  is an anion; 
 each occurrence of R 2  is independently selected from the group consisting of alkyl, halogen, nitro, cyano, trifluoromethyl, trichloromethyl, carboxy, formyl, lower alkanoyl, carboxyamido and aryl lower alkanoyl; 
 R 3  is alkyl, alkyl(aryl) or aryl, all of which are optionally substituted; and 
 M is selected from the group consisting of Mo, W. Re and Ta, 
 
       with the proviso that, if R 1  is selected from the group consisting of N and P, at least one occurrence of n is not zero. 
     
     
         18 . The method of  claim 17 , wherein the compound of formula (IV) is 
       
         
           
           
               
               
           
         
       
     
     
         19 - 20 . (canceled)