Process for the preparation of exametazime

1. A process for the preparation of exametazime (formula I),

which comprises the steps of:

a) reacting 2,3-butanedione monoxime (formula II) with 2,2-dimethyl-1,3-propanediamine (formula III), in a suitable solvent, in presence of a dehydrating agent to afford diimine derivative 4,8-diaza-3,6,6,9-tetramethylundecane-3,8-diene-2,10-dione bisoxime (formula IV),

b) reducing diimine derivative 4,8-diaza-3,6,6,9-tetramethylundecane-3,8-diene-2,10-dione bisoxime (formula IV) with a suitable reducing agent in a suitable solvent to afford a mixture of ‘d’, ‘l’ and meso isomers,

c) optionally, purifying the mixture of ‘d’, ‘l’ and meso isomers,

d) treating the mixture of ‘d’, ‘l’ and meso isomers with d or l chiral resolving acid to form corresponding acid addition salts, which are enantiomers of exametazime, and separating one of the enantiomers of exametazime as an acid addition salt,

e) optionally, purifying the acid addition salt obtained in step (d),

f) treating the mother liquor of step (d) with a suitable base,

g) isolating a mixture of ‘d’ or ‘l’ enantiomers and meso isomers,

h) purifying the mixture obtained in step (g),

i) treating the mixture from step (h) with l or d chiral resolving acid to form corresponding acid addition salts, which are other enantiomers of exametazime and separating said other enantiomers of exametazime as acid addition salts,

j) optionally, purifying the acid addition salts obtained in step (i),

k) mixing the acid addition salt of step (d) or (e) and step (i) or (j),

l) optionally, purifying the mixture of acid addition salts obtained in step (k),

m) treating the mixture of acid addition salts of step (k) or (1) with a suitable base to afford exametazime and,

n) optionally, purifying the exametazime.

2. The process according to claim 1 , wherein the dehydrating agents is selected from the group consisting of calcium hydride, molecular sieves, magnesium sulphate and sodium sulphate.

3. The process according to claim 1 , wherein the chiral resolving acid is selected from the group consisting of L-(+) tartaric acid, D-(−) tartaric acid, L-malic acid, D-malic acid, S-(+) mandelic acid, R-(−) mandelic acid, S-(+)-O-acetyl mandelic acid, R-(−)-O-acetyl mandelic acid, (−)-naproxen, (+)-naproxen, (1R)-(−)-camphor sulfonic acid, (1S)-(+)-camphor sulfonic acid, (1R)-(+)-bromocamphor-10-sulfonic acid, (1S)-(−)-bromocamphor-10-sulfonic acid, (−)-Dibenzoyl-L-tartaric acid, (−)-Dibenzoyl-L-tartaric acid monohydrate, (+)-Dibenzoyl-D-tartaric acid, (+)-Dibenzoyl-D-tartaric acid monohydrate, (+)-dipara-tolyl-D-tataric acid, (−)-dipara-tolyl-L-tataricacid, L(−)-pyroglutamic acid, L(+)-pyroglutamic acid, (+)-lactic acid, (−)-lactic acid, (S)-(+)-2-chloromandelic acid, and (R)-(−)-2-chloromandelic acid.

4. The process according to claim 1 , wherein the ‘d’ and ‘l’ mixture of chiral resolving acid is selected from the group consisting of (±) tartaric acid, (±) malic acid, (±) ascorbic acid, (±) mandelic acid, (±)-O-acetyl mandelic acid, (±) naproxen, (±) camphor sulfonic acid, (±) bromocamphor-10-sulfonic acid, (±) Dibenzoyl-tartaric acid, (±) dipara-tolyl-tataric acid, (±) pyroglutamic acid, (±) lactic acid, and (±)-2-chloromandelic acid.

5. The process according to claim 1 , wherein the suitable bases is selected from the group consisting of sodium hydroxide, potassium hydroxide, sodium carbonate, potassium carbonate, sodium bicarbonate, and potassium bicarbonate, either alone or as their aqueous solutions.

6. The process according to claim 1 , wherein the suitable solvents is selected from the group consisting of nitriles, alcohols, esters, halogenated hydrocarbons, ethers, amides, dialkylsulfoxides, hydrocarbons, water and a mixture thereof; with the proviso that ketones/nitriles are not used during the reduction reaction of diimine derivative 4,8-diaza-3,6,6,9-tetramethylundecane-3,8-diene-2,10-dione bisoxime (formula IV); and water is avoided in condensation of 2,3-butanedione monoxime (formula II) with 2,2-dimethyl-1,3-propanediamine (formula III).