Synthesis of isohexide ethers and carbonates

Abstract

A facile, straightforward method for alkylation of anhydrosugar alcohols (isohexides) using a carbonate reagent is described. The alkylation method involves: a) contacting in a solution of an isohexide with a dialkyl, diallyl, or diaryl carbonate, and the solution includes a Brønsted base; and b) producing either an alkyl ether or alkyl carbonate of the isohexide compound. The alkylation reaction is in situ, that is, performed without an extrinsic catalyst. According to the method, one can synthesize various ethers and carbonates.

We claim: 
     
         1 . A method of alkylating an anhydrosugar compound comprising: a) contacting an isohexide compound with a dialkyl, diallyl, or diaryl carbonate and a Brønsted base; and b) producing at least an alkyl ether or alkyl carbonate of the isohexide compound. 
     
     
         2 . The method according to  claim 1 , wherein the anhydrosugar compound is at least one of: isosorbide, isomannide, and isoidide. 
     
     
         3 . The method according to  claim 1 , wherein said dialkyl, diallyl, or diaryl carbonate has an R-group having 1 to 20 carbon atoms. 
     
     
         4 . The method according to  claim 3 , wherein when said R-group is at least one of methyl, ethyl, propyl group, said alkyl ether is produced predominantly. 
     
     
         5 . The method according to  claim 3 , wherein when said R-group is at least a C 4 -C 20  group, said alkyl carbonate is produced predominantly. 
     
     
         6 . The method according to  claim 1 , wherein said alkylated ether of said isohexide compound is at least one of: mono-ether of isoidide, mono-ether of isomannide, mono-ether of isosorbide, di-ether of isoidide, di-ether of isomannide, and di-ether of isosorbide. 
     
     
         7 . The method according to  claim 3 , wherein said alkylated isohexide compound is an ether having at least one of the following alkyl groups: a mono-methyl, mono-ethyl, mono-propyl, di-methyl, di-ethyl, or di-propyl isohexide ether. 
     
     
         8 . The method according to  claim 1 , wherein said alkylated carbonate of said isohexide compound is at least one of: mono-carbonate of isoidide; mono-carbonate of isomannide; mono-carbonate of isosorbide; di-carbonate of isoidide; di-carbonate of isomannide; and di-carbonate of isosorbide. 
     
     
         9 . The method according to  claim 5 , wherein said alkylated isohexide compound is a carbonate having at least one of the following alkyl, allyl or aryl groups: a mono-butyl, mono-pentyl, mono-hexyl, mono-benzyl, mono-phenyl, mono-allyl, di-butyl, di-pentyl, dihexyl, di-benzyl, di-phenyl, di-allyl, or a mono- or di-alkyl group from C 7 -C 20  carbon atoms. 
     
     
         10 . The method according to  claim 1 , wherein said anhydrosugar compound and said dialkyl, diallyl, or diaryl carbonate are contacted at a temperature in a range from about 70° C. to about 200° C. 
     
     
         11 . The method according to  claim 10 , wherein said anhydrosugar compound and said dialkyl, diallyl, or diaryl carbonate are contacted at a temperature in arrange from about 80° C. to about 150° C. 
     
     
         12 . The method according to  claim 1 , wherein said anhydrosugar compound and said dialkyl, diallyl, or diaryl carbonate are contacted in a neat solution of said dialkyl, diallyl, or diaryl carbonate. 
     
     
         13 . The method according to  claim 1 , wherein said Brønsted base has a pKa of at least 4. 
     
     
         14 . The method according to  claim 13 , wherein said Brønsted base has a pKa 7-14. 
     
     
         15 . The method according to  claim 1 , wherein said Brønsted base is at least one of the following: a carbonate; a hindered amine; a nucleophilic base; a sodium, potassium or calcium hydride; or an organometallic compound. 
     
     
         16 . The method according to  claim 15 , wherein said organometallic compound is an alkyl-lithium or alkyl-magnesium. 
     
     
         17 . An ether compound prepared according to the method of  claim 1 , wherein said ether compound is at least one of the following: a monoalkyl ether or dialkyl ether. 
     
     
         18 . The ether compound according to  claim 17 , wherein said ether compound has a structure: 
       
         
           
           
               
               
           
         
       
       wherein for a dialkyl ether, R is a C 1 -C 3  alkyl group; and, for a monoalkyl ether, one R is a C 1 -C 3  alkyl group and another is an OH. 
     
     
         19 . The ether compound according to  claim 17 , wherein said ether compound is at least:
 an isoidide monoethylether, with a structure:   
       
         
           
           
               
               
           
         
         an isoidide diethylether, with a structure: 
       
       
         
           
           
               
               
           
         
       
     
     
         20 . The alkylated isohexide compound according to  claim 17 , wherein said compound is an ether selected from the group consisting of: mono-methyl ether of isoiodide; mono-ethyl ethers, of isosorbide, isommanide, or isoiodide, respectively; diethyl ester of isoiodide; mono-propyl ether of isomannide; dipropyl ether of isomannide; mono-propyl ether of isoidide; dipropyl ether of isoiodide; mono-benzyl ether of isoidide; monoallyl ethers of isosorbide, isommanide, or isoiodide, respectively; and diallyl ethers of isosorbide, isommanide, or isoiodide, respectively. 
     
     
         21 . A carbonate compound prepared according to the method of  claim 1 , wherein said carbonate compound is at least one of the following: a mono-alkyl carbonate, dialkyl carbonate, mono- or di-aryl carbonate, mono- or di-allyl carbonate, or a carbonate with an alkyl group from 4-20 carbon atoms. 
     
     
         22 . The carbonate compound according to  claim 21 , wherein said carbonate compound has a structure: 
       
         
           
           
               
               
           
         
       
       wherein for a dialkyl carbonate, R is a C 4  or higher carbon alkyl, phenyl, allyl group; and, for a monoalkyl ether, one R is a C 4  or higher carbon alkyl, phenyl, allyl group and another is an OH. 
     
     
         23 . The carbonate compound according to  claim 21 , wherein said carbonate compound is: isosorbide diallyldicarbonate, with a structure: 
       
         
           
           
               
               
           
         
       
     
     
         24 . The alkylated isohexide compound according to  claim 21 , wherein said compound is a carbonate selected from the group consisting of: mono-methylcarbonate of isomannide; mono-methylcarbonate of isoidide; dimethylcarbonate of isomannide; dimethylcarbonate of isoidide; monoethylcarbonates of isosorbide, isommanide, or isoiodide; diethylcarbonate of isomannide; diethylcarbonate of isoidide; mono-propyl or dipropylcarbonates of isosorbide, isommanide, or isoiodide; mono- or dicarbonates having an alkyl R-group of C 4  to C 20  of isosorbide, isommanide, or isoiodide, respectively; mono-benzyl or dibenzyl carbonates of isosorbide, isommanide, or isoiodide, respectively; monophenylcarbonates of isosorbide, isommanide, or isoiodide, respectively; and diphenylcarbonates of isomannide or isoidide.