Process for the preparation of sunitinib and its acid addition salts thereof

1. A process for the preparation of sunitinib of Formula I or acid addition salts thereof,

the process comprising the steps of:

a) reacting 5-((Z)-(5-fluoro-2-oxoindolin-3-yliden) methyl)-2,4-dimethyl-1H-pyrrole-3-carboxylic acid of Formula II

with a sulfonylating agent to obtain an activated compound of Formula III,

wherein X represents a sulfonyl; and

b) amidating the compound of Formula III with N, N-diethyl ethylene diamine in an organic solvent to obtain sunitinib.

2. The process of claim 1 , wherein the sulfonyl group is an alkyl sulfonyl or aryl sulfonyl, wherein alkyl represents C 1-4 linear or branched chain alkyl and aryl represents alkyl substituted or unsubstituted phenyl group.

3. The process of claim 1 , wherein the sulfonylating agent is p-toluene sulfonyl chloride and the sulfonyl is p-toluene sulfonyl.

4. The process of claim 1 , wherein step a) is carried out in presence of a base and a catalyst in an organic solvent.

5. The process of claim 4 , wherein the base is selected from the group consisting of triethylamine, tributylamine, diisopropylethylamine, diethylamine, N-methylmorpholine, pyridine, N,N-dimethylaniline, N,N-diethylaniline, and mixtures thereof.

6. The process of claim 4 , wherein the organic solvent is selected from the group consisting of formamide, dimethylformamide, dimethylacetamide, hexamethylphosphoric triamide, and mixtures thereof.

7. The process of claim 4 , wherein the catalyst is N, N-dimethyl amino pyridine.

8. The process of claim 1 , wherein the organic solvent of step b) is selected from the group consisting of formamide, dimethylformamide, dimethylacetamide, hexamethylphosphoric triamide, and mixtures thereof.

9. The process of claim 1 , wherein step a) is carried out in presence of pyridine, N, N-dimethyl amino pyridine, and dimethylformamide.

10. The process of claim 1 , further comprising the step of c) treating the sunitinib base with malic acid to obtain sunitinib malate salt.

11. A compound of formula III

wherein X represents a sulfonyl.

12. The compound of claim 11 , wherein X is p-toluene sulfonyl.

13. A process for the preparation of compound of formula III

wherein X represents a sulfonyl,

or a pharmaceutically acceptable salt thereof, the process comprising the step of reacting 5-((Z) -(5-fluoro-2-oxoindolin-3-ylidene) methyl)-2,4-dimethyl-1H-pyrrole-3-carboxylic acid of Formula II

with a sulfonylating agent in presence of a base and a catalyst in an organic solvent to form a compound of Formula III.