Preparation of opiates

Abstract

A novel process for the preparation of codeinone and analogues thereof comprising the oxidation of a compound of formula, or a salt thereof, wherein R 1 is lower alkyl or a group wherein R 4 is lower alkyl, lower alkyl substituted by halogen or phenyl, phenyl or substituted phenyl; and R 2 is lower alkyl, allyl or lower alkyl substituted by cycloalkyl, characterised in that the oxidation is carried out in an acidic environment is disclosed.

1 . A process for the preparation of a compound of formula (I)  
                   wherein R 1  is lower alkyl or a group  
                 
   wherein R 4  is lower alkyl, lower alkyl substituted by halogen or phenyl. phenyl or substituted phenyl; and    R 2  is lower alkyl, allyl or lower alkyl substituted by cycloalkyl;    comprising the oxidation of a compound of formula (II),  
                 
   or a salt thereof, wherein R 1  and R 2  are as hereinbefore defined, characterised in that the oxidation is carried out in an acidic environment:    
     
     
         2 . A process according to    claim 1    wherein each of R 1  and R 2  may be the same or different and each is lower alkyl.  
     
     
         3 . A process according to    claim 2    wherein each of R 1  and R 2  may be the same or different and is methyl or ethyl.  
     
     
         4 . A process according to    claim 3    wherein R 1  and R 2  are both ethyl.  
     
     
         5 . A process according to any one of    claims 1    to    4    wherein when the compound of formula (II) is present as a salt, the salt is the phosphate salt.  
     
     
         6 . A process according to any one of    claims 1    to    5    wherein the oxidation is carried out at a pH of between 0.1 and 7.  
     
     
         7 . A process according to    claim 6    wherein the oxidation is carried out at a pH of between 0.8 and 4.5.  
     
     
         8 . A process according to    claim 7    wherein the oxidation is carried out at a pH of from 0.8 to 1.2.  
     
     
         9 . A process according to any one of    claims 1    to    8    wherein the oxidation reagent is manganese dioxide.