Yield-efficient process for the production of highly pure 2-methyl-1, 4-naphthoquinone and its derivatives

Abstract

The present invention discloses a process for the production of 2-methyl-1,4-naphthoquinone and its bisulfite adducts, comprising the following steps: a) oxidizing 2-methyl-naphthalene (2-MNA) to achieve an organic phase containing 2-methyl-naphthoquinone (2-MNQ) and 6-methyl-naphthoquinone (6-MNQ); b) subjecting said organic phase to treatment with an aqueous solution of a bisulfite salt to extract preferentially the 6-MNQ isomer from the organic phase; c) separating said organic phase from the aqueous phase; d) subjecting the organic phase of process step c) to a second bisulfitation step with an aqueous solution of a bisulfite salt, resulting in an organic phase containing 2-MNA and trace amounts of 2-MNQ and an aqueous phase containing 2-MSB and trace amounts of 6-MSB; e) optionally removing interfering bisulfite ions from the aqueous phase of process step c); f) raising the pH of the aqueous phase from step c) or e) to higher than 8.5 in the presence of a solvent resulting in an organic phase containing 2-MNQ; g) combining the organic phase from step f) with the organic phase being treated in the process step d); h) recycling the organic phase from step d) back to step a) to be used as solvent for the oxidation reaction of 2-MNA.

1 . A process for the production of 2-methyl-1,4-naphthoquinone and its bisulfite adducts, comprising the following steps:
 a) oxidizing 2-methyl-naphthalene (2-MNA) to achieve an organic phase containing 2-methyl-naphthoquinone (2-MNQ) and 6-methyl-naphthoquinone (6-MNQ);   b) subjecting said organic phase to treatment with an aqueous solution of a bisulfite salt to extract preferentially the 6-MNQ isomer from the organic phase;   c) separating said organic phase from the aqueous phase;   d) subjecting the organic phase of process step c) to a second bisulfitation step with an aqueous solution of a bisulfite salt, resulting in an organic phase containing 2-MNA and trace amounts of 2-MNQ and an aqueous phase containing 2-MSB and trace amounts of 6-MSB;   e) optionally removing interfering bisulfite ions from the aqueous phase of process step c);   f) raising the pH of the aqueous phase from step c) or e) to higher than 8.5 in the presence of a solvent resulting in an organic phase containing 2-MNQ;   g) combining the organic phase from step f) with the organic phase being treated in the process step d);   h) recycling the organic phase from step d) back to step a) to be used as solvent for the oxidation reaction of 2-MNA.   
     
     
         2 . The process according to  claim 1 , whereby the organic phase from step c) is used to produce pure solid 2-MNQ by cooling and by separating the precipitated 2-MNQ by any known solid-liquid separation method before being subjected to the second bisulfitation in step d). 
     
     
         3 . The process according to  claim 1 , whereby said aqueous phase from process step d) is isolated and the bisulfite adduct of the 2 isomer is precipitated and isolated or used as a reactant to prepare other Vitamin K3 derivatives. 
     
     
         4 . Process according to  claim 1 , whereby the step e) for the removal of interfering bisulfite ions is effected by a method selected from the group consisting of selective precipitation, ion exchange treatment, membrane treatment or conversion into inert ions. 
     
     
         5 . The process according to  claim 1 , whereby process step f) is performed in the absence of an organic solvent and the 2-MNQ is isolated as a precipitated solid by any solid-liquid separation method. 
     
     
         6 . The process according to  claim 1 , whereby process step a) preferably takes place at a temperature in the range of 0-100° C. more preferably 25-60° C. and most preferably 25-40° C. 
     
     
         7 . The process according to  claim 1 , whereby process step a) employs an oxidizing agent selected from the group consisting of a Ce(III)/Ce(IV) salt redox couple. 
     
     
         8 . The process according to  claim 7 , whereby the spent cerium salt is re-oxidized by using an electrochemical cell. 
     
     
         9 . The process according to  claim 1 , whereby process step b) as well as process step d) are carried out at a temperature in the range of 0-70° C., more preferably 10-50° C. and most preferably 25-40° C. 
     
     
         10 . The process according to  claim 1 , whereby process step b) as well as process step d) use a solution containing a bisulfite salt, preferably selected from the group consisting of sodium or potassium bisulfite. 
     
     
         11 . The process according to  claim 1 , whereby said bisulfite solution in process step b) preferably has a concentration of 0.1-4 M, more preferably 0.5-2 M and most preferably 0.5 M.