Method for the production of praziquantel

1. A method which comprises racemization of enantiomerically pure or enantiomerically enriched Praziquantel:

wherein a base is used and the base is a tertiary alkyl alkoxide.

2. A method according to claim 1 , wherein the tertiary alkali alkoxide used for the racemization is potassium tert.-butoxide.

3. A method according to claim 1 , wherein the racemization is a performed in a dipolar aprotic reaction medium.

4. A method according to claim 3 , wherein the dipolar aprotic reaction medium is selected from the group consisting of N-Methyl-2-pyrrolidone, dimethylformamide, dimethylsulfoxide, tetrahydrofuran, methyltetrahydrofuran, dioxane and mixtures thereof in all ratios.

5. A method according to claim 1 , wherein the racemization is performed at a temperature in a range between −50° C. and +40° C.

6. A method according claim 1 , wherein the amount of base used for the racemization is in the range of 0.05 eq to 1.5 eq.

7. A method according to claim 1 , wherein:

the racemization is performed in a dipolar aprotic reaction medium selected from a group consisting of N-Methyl-2-pyrrolidone, dimethylformamide, dimethylsulfoxide, tetrahydrofuran, methyltetrahydrofuran, dioxane and mixtures thereof in all ratios;

the amount of base used for the racemization is in the range between 0.05 eq to 1.5 eq;

the racemization is performed at a temperature in the range between −50° C. and +40° C.

8. A method for the production of (R)-Praziquantel in enantiopure or enantiomerically enriched form, comprising following steps:

a. Racemization of enantiomerically pure or enantiomerically enriched (S)-Praziquantel according to claim 1 ; and

b. Chiral resolution of the mixture of the enantiomers (S)-(I) and (R)-Praziquantel obtained in a).

9. A method according to claim 8 , wherein the chiral resolution according to step b) is performed using chromatography.