Process for the electrochemical preparation of gamma-hydroxycarboxylic esters and gamma-lactones

Abstract

γ-Hydroxycarboxylic esters and γ-lactones which are suitable as flavors can be prepared by electrochemical reductive cross-coupling of α,β-unsaturated esters with carbonyl compounds in an undivided electrolysis cell having a cathode composed of lead, lead alloys, cadmium, cadmium alloys, mercury, steel, glassy carbon or boron-doped diamonds and a basic aqueous electrolyte comprising an electrolyte salt which suppresses the cathodic formation of hydrogen.

1 . A γ-butyrolactone derivative of formula I 
       
         
           
           
               
               
           
         
         wherein 
         R1, R2 and R3 are each independently a hydrogen or an alkyl group having from 1 to 5 carbon atoms,. and 
         R4 and R5 are alkyl groups having from 1 to 4 carbon atoms, with R4 and R5 being identical radicals. 
       
     
     
         2 . The γ-butyrolactone derivative according to  claim 1 , wherein the derivative is selected from the group consisting of 4-(2-pentyl)butyrolactone and 3 -methyl-4-(2-pentyl)butyrolactone. 
     
     
         3 . The γ-butyrolactone derivative according to  claim 1 , wherein the derivative is a flavor. 
     
     
         4 . A γ-hydroxycarboxylic acid or γ-hydroxycarboxylic ester of formula VII 
       
         
           
           
               
               
           
         
         wherein 
         R1, R2, R3 and R7 are each independently, a hydrogen or an alkyl group having from 1 to 5 carbon atoms, 
         R is a hydrogen or an alkyl group, and 
         R8 is a branched alkyl group having from 3 to 10 carbon atoms. 
       
     
     
         5 . The γ-hydroxycarboxylic acid or γ-hydroxycarboxylic ester according to  claim 4 , wherein R7 is a hydrogen.