Synthesis of r-glucosides, sugar alcohols, reduced sugar alcohols, and furan derivatives of reduced sugar alcohols

Abstract

Disclosed herein are methods for synthesizing 1,2,5,6-hexanetetrol (HTO), 1,6 hexanediol (HDO) and other reduced polyols from C5 and C6 sugar alcohols or R glycosides. The methods include contacting the sugar alcohol or R-glycoside with a copper catalyst, most desirably a Raney copper catalyst with hydrogen for a time, temperature and pressure sufficient to form reduced polyols having 2 to 3 fewer hydoxy groups than the starting material. When the starting compound is a C6 sugar alcohol such as sorbitol or R-glycoside of a C6 sugar such as methyl glucoside, the predominant product is HTO. The same catalyst can be used to further reduce the HTO to HDO.

1 . A method of making a reduced sugar alcohol including at least one member selected from the group consisting of 1,2,5-pentanetriol, 1,4,5-hexanetriol, 1,2,6-hexanetetrol, and 1,2,5,6 hexanetetrol, comprising,
 contacting a solution comprising water and at least 20% wt/wt of a starting compound selected from the group consisting of a sugar alcohol and a R-glycoside of a sugar, wherein R is a methyl or ethyl group, with hydrogen and a Raney copper catalyst for a time and at a temperature and pressure sufficient to produce a mixture containing one or more of the reduced sugar alcohols with a combined selectively yield of at least 50% mol/mol.   
     
     
         2 . The method of  claim 1 , wherein the starting compound is a C6 sugar alcohol selected from the group consisting of sorbitol, mannitol, ididtol, dulcitol, talitol, and 1,4-sorbitan and the reduced sugar alcohol is at least one of 1,4,5-hexanetriol and 1,2,5,6-hexanetetrol. 
     
     
         3 . The method of  claim 1  wherein the starting compound is a methyl or ethyl glucoside and reduced sugar alcohol is at least one of 1,4,5-hexanetriol and 1,2,5,6-hexanetetrol. 
     
     
         4 . The method of  claim 1 , wherein the temperature is 175° C. to 250° C. and the pressure is between 500 psi and 2500 psi. 
     
     
         5 . The method of  claim 1  wherein the solution comprises 20-30% wt/wt water and 45-55% of a C2-C3 glycol. 
     
     
         6 . The method of  claim 1  wherein the solution comprises 20-30% wt/wt water and 50-55% wt/wt propylene glycol. 
     
     
         7 . The method of  claim 6  wherein the combined selectivity yield is at least 70% mol/mol. 
     
     
         8 . The method of  claim 6  wherein the starting compound is sorbitol and the reduced sugar alcohol is predominantly 1,2,5,6-hexanetetrol formed at a yield of at least 35% mol/mol.
   9 . The method of  claim 6  wherein the wherein the starting compound is a methyl or ethyl glucoside and the reduced sugar alcohol is predominantly 1,2,5,6-hexanetetrol formed at yield of at least 35% mol/mol. 
 
     
     
         10 . The method of claim  9  further comprising contacting the 1,2,5,6-hexanetetrol with an acid selected from the group consisting of sulfuric acid, phosphonic acid, carbonic acid and a water tolerant non-Bronsted Lewis acid for a time sufficient to form 2,5 bis(hydoxymethyl) tetrahydofuran. 
     
     
         11 . The method of  claim 10  wherein the 1,2,5,6-hexanetetrol is separated from the mixture prior to contacting with the acid. 
     
     
         12 . The method of  claim 1  wherein the starting compound is a C5 sugar alcohol selected from the group consisting of xylitol, ribotol, and arabinitol and the reduced sugar alcohol is predominantly 1,2,5-pentanetriol. 
     
     
         13 . The method of  claim 1  wherein the Raney copper catalyst is deployed as a fixed bed catalyst in a reactor. 
     
     
         14 . The method of  claim 1  wherein the starting compound is at least 25% wt/wt of the solution. 
     
     
         15 . A method of making 1,2,5,6-hexanetetrol comprising, contacting a solution comprising 20-30% wt/wt water, 45-55%) of propylene
 glycol and at least 20% wt/wt of a starting compound selected from the group consisting of C6 sugar alcohol and a R-glycoside of a C6 sugar, wherein R is a methyl or ethyl group, with hydrogen and a Raney copper catalyst for a time and at a temperature and pressure sufficient to produce a mixture containing the 1,2,5,6-hexanetetrol with a selectively yield of at least 35% wt/wt.   
     
     
         16 . The method of  claim 15 , wherein the selectivity yield for 1,2,5,6-hexanetetrol is at least 40% wt/wt. 
     
     
         17 . The method of  claim 15 , wherein the Raney copper catalyst is deployed as a fixed bed in a reactor. 
     
     
         18 . (canceled) 
     
     
         19 . The method of  claim 15  wherein the propylene glycol is 50-55% wt/wt of the solution and the starting compound is at least 25% wt/wt of the solution. 
     
     
         20 . The method of  claim 15  further comprising contacting the 1,2,5,6-hexanetetrol with an acid selected from the group consisting of sulfuric acid, carbonic acid, phosphonic acid and a water tolerant non-Bronsted Lewis acid for a time sufficient to form 2,5 bis(hydoxymethyl) tetrahydofuran. 
     
     
         21 . The method of  claim 20  wherein the 1,2,5,6-hexanetetrol is separated from the mixture prior to contacting with the acid.