Lewis acid catalyzed halogenation of activated carbon atoms

Abstract

A practical and efficient method for halogenation of activated carbon atoms using readily available N-haloimides and a Lewis acid catalyst has been disclosed. This methodology is applicable to a range of compounds and any halogen atom can be directly introduced to the substrate. The mild reaction conditions, easy workup procedure and simple operation make this method valuable from both an environmental and preparative point of view.

1 . A method of halogenating an activated carbon atom in the presence of a Lewis acid comprising,
 reacting a material comprising an activated carbon atom with a halogen donor in the presence of a catalytic amount of the Lewis acid;   wherein the Lewis acid comprises a metal selected from the group consisting of Zr, Fe, and Al;   wherein the activated carbon atom is an aromatic carbon atom, a carbon atom alpha to an aromatic ring, or a carbon atom alpha to a silicon atom; and   wherein the halogen donor is selected from the group consisting of N-bromosuccinimide, N-iodosuccinimide, N-chlorosuccinimide and N-fluorobenzene-sulfonimide.   
     
     
         2 . The method of  claim 1 , wherein the Lewis acid is Zr. 
     
     
         3 . The method of  claim 2 , wherein the Lewis acid is ZrCl 4 . 
     
     
         4 . The method of  claim 1 , wherein the material is an aromatic compound represented by formula I: 
       
         
           
           
               
               
           
         
         wherein:
 Ring A is aryl; 
 R 1  is selected from the group consisting of —OR 3 , —NR 3 R 4 , and —SR 3 ; 
 wherein R 3  and R 4  are each independently selected from the group consisting of hydrogen, C 1-8  alkyl, C 1-8  heteroalkyl, C 2-8  alkenyl, C 2-8  alkynyl, C 6-10  aryl, 5- to 10-membered heteroaryl, and 3- to 10-membered heterocycle;
 R 3  and R 4  may together with the atom(s) to which they are attached, form a 5-, 6-, or 7-membered cycloalkyl or heterocyclyl; 
 
 
         R 2  represents 0 to 5 substituents each independently selected from the group consisting of hydrogen, —OR 3 , —NR 3 R 4 , —SR 3 , C 1-8  alkyl, C 1-8  heteroalkyl, C 1-8  haloalkyl, C 2-8  alkenyl, C 2-8  alkynyl, 3- to 10-membered heterocyclyl, C 6-10  aryl, and 5- to 10-membered heteroaryl. 
       
     
     
         5 . The method of  claim 1 , wherein the material is an aromatic compound represented by formula III: 
       
         
           
           
               
               
           
         
         wherein:
 Ring A is heteroaryl; and 
 R 2  represents 0 to 5 substituents each independently selected from the group consisting of hydrogen, C 1-8  alkyl, C 1-8  heteroalkyl, C 1-8  haloalkyl, C 2-8  alkenyl, C 2-8  alkynyl, 3- to 10-membered heterocyclyl, C 6-10  aryl, and 5- to 10-membered heteroaryl. 
 
       
     
     
         6 . The method of  claim 5 , wherein the aromatic compound is represented by formula IIIa: 
       
         
           
           
               
               
           
         
         wherein: 
         R 2  represents 0 to 4 substituents each independently selected from the group consisting of hydrogen, halogen, C 1-8  alkyl, C 1-8  heteroalkyl, C 1-8  haloalkyl, C 2-8  alkenyl, C 2-8  alkynyl, 3- to 10-membered heterocyclyl, C 6-10  aryl, and 5- to 10-membered heteroaryl; 
         Y 1  is selected from the group consisting of —NR 3 —, —O—, and —S—; 
         each Y 2  is independently —CR 3 R 4 —; 
         Y 3  is selected from the group consisting of —NR 3 —, —O—, —CR 3 R 4 — and —S—;
 wherein R 3  and R 4  are each independently selected from the group consisting of hydrogen, C 1-8  alkyl, C 1-8  heteroalkyl, C 2-8  alkenyl, C 2-8  alkynyl, C 6-10  aryl, 5- to 10-membered heteroaryl, and 3- to 10-membered heterocycle;
 R 3  and R 4  may together with the atom(s) to which they are attached, form a 5-, 6-, or 7-membered cycloalkyl or heterocyclyl; and 
 
 
         n is 1, 2 or 3. 
       
     
     
         7 . The method of  claim 5 , wherein the aromatic compound is represented by formula IIIb: 
       
         
           
           
               
               
           
         
         wherein Y 1  is selected from the group consisting of —NR 3 —, —O—, and —S—. 
       
     
     
         8 . The method of  claim 1 , wherein the activated carbon atom is alpha to an aromatic ring and the material is represented by formula V: 
       
         
           
           
               
               
           
         
         wherein: 
         Ring A is aryl; 
         R 3  and R 4  are each independently selected from the group consisting of hydrogen, C 1-8  alkyl, C 1-8  heteroalkyl, C 2-8  alkenyl, C 2-8  alkynyl, C 6-10  aryl, 5- to 10-membered heteroaryl, and 3- to 10-membered heterocycle;
 R 3  and R 4  may together with the atom(s) to which they are attached, form a 5-, 6-, or 7-membered cycloalkyl or heterocyclyl; and 
 
         R 5  represents 0 to 5 substituents each independently selected from the group consisting of hydrogen and halogen. 
       
     
     
         9 . The method of  claim 1 , wherein the material is elemental carbon comprising an aromatic carbon compound. 
     
     
         10 . The method of  claim 9 , wherein the material is graphite or charcoal. 
     
     
         11 . The method of  claim 1 , wherein the activated carbon atom is alpha to silicon and the material is represented by formula VIIa: 
       
         
           
           
               
               
           
         
         wherein
 R 2  is independently selected from the group consisting of hydrogen, —OR 3 , —NR 3 R 4 , —SR 3 ,C 1-8  alkyl, C 1-8  heteroalkyl, C 1-8  haloalkyl, C 2-8  alkenyl, C 2-8  alkynyl, 3- to 10-membered heterocyclyl, C 6-10  aryl, and 5- to 10-membered heteroaryl; and 
 R 3  and R 4  are each independently selected from the group consisting of hydrogen, C 1-8  alkyl, C 1-8  heteroalkyl, C 2-8  alkenyl, C 2-8  alkynyl, C 6-10  aryl, 5- to 10-membered heteroaryl, and 3- to 10-membered heterocycle. 
 
       
     
     
         12 . A halogenated elemental carbon prepared by the steps of:
 reacting elemental carbon comprising an aromatic carbon compound with a halogen donor in the presence of a catalytic amount of the Lewis acid to form halogenated elemental carbon;   wherein the Lewis acid comprises a metal selected from the group consisting of Zr, Fe, and Al;   wherein the halogen donor is selected from the group consisting of N-bromosuccinimide, N-iodosuccinimide, N-chlorosuccinimide and N-fluorobenzene-sulfonimide.   
     
     
         13 . The halogenated elemental carbon of  claim 12 , wherein the elemental carbon is graphite or charcoal. 
     
     
         14 . The halogenated elemental carbon of  claim 12 , wherein the Lewis acid comprises Zr. 
     
     
         15 . The halogenated elemental carbon of  claim 12 , wherein the Lewis acid is ZrCl 4 . 
     
     
         16 . A catalyst prepared by the steps of:
 halogenating elemental carbon comprising an aromatic carbon compound to form halogenated elemental carbon;   reacting the elemental carbon with a halogen donor in the presence of a catalytic amount of a Lewis acid wherein the Lewis acid comprises a metal selected from the group consisting of Zr, Fe, and Al;   coupling a functional group to the halogenated elemental carbon to form a functionalized elemental carbon; and   complexing a metal to the functionalized elemental carbon.   
     
     
         17 . The catalyst of  claim 16 , wherein the Lewis acid is ZrCl 4 . 
     
     
         18 . The catalyst of  claim 16 , wherein the elemental carbon is graphite or charcoal; wherein the halogen donor is selected from the group consisting of N-bromosuccinimide, N-iodosuccinimide, N-chlorosuccinimide and N-fluorobenzene-sulfonimide; and wherein the Lewis acid comprises a metal selected from the group consisting of Zr, Fe, and Al. 
     
     
         19 . A method of halogenating an activated carbon atom in the presence of a Lewis acid comprising,
 reacting a material comprising an activated carbon atom with a halogen donor in the presence of a catalytic amount of the Lewis acid;   wherein the Lewis acid is Zr;   wherein the activated carbon atom is an aromatic carbon atom, a carbon atom alpha to an aromatic ring, or a carbon atom alpha to a silicon atom; and   wherein the reacting is done in the presence of light.   
     
     
         20 . The method of  claim 19 , wherein the light is laser light. 
     
     
         21 . A method of halogenating an activated carbon atom in the presence of a Lewis acid comprising,
 reacting a material comprising an activated carbon atom with a halogen donor in the presence of a catalytic amount of the Lewis acid;   wherein the Lewis acid comprises a metal selected from the group consisting of Zr, Fe, and Al;   wherein the activated carbon atom is an aromatic carbon atom, a carbon atom alpha to an aromatic ring, or a carbon atom alpha to a silicon atom; and   wherein the halogen donor is a 1,3-dihalo-5,5-dimethylimidazolidine-2,4-dione.   
     
     
         22 . The method of  claim 21 , wherein the halogen donor is 1,3-dibromo-5,5-dimethyl imidazolidine-2,4-dione.