Process for large scale production of 1-[(2-bromophenyl)sulfonyl]-5-methoxy-3-[(4-methyl-1-piperazinyl)methyl]-1H-indole dimesylate monohydrate

A process suitable for large scale production of 1-[(2-bromophenyl)sulfonyl]-5-methoxy-3-[(4-methyl-1-piperazinyl)methyl]-1H-indole dimesylate monohydrate of formula (I),

• which comprises:
• Step (i):
• reacting 1-methylpiperazine of formula 1
• in presence of acetic acid and aqueous formaldehyde of formula 2
• HCHO 2
• at a temperature in the range of 15° C. to 35° C. for a period of 1.5 hours to 2.5 hours to obtain Mannich adduct;
• Step (ii):
• reacting the Mannich adduct with 5-methoxyindole of formula 3
• in presence of methanol at a temperature in the range of 15° C. to 40° C. for a period of 2.5 hours to 3.5 hours to obtain 5-methoxy-3-[(4-methyl-1-piperazinyl) methyl]-1H-indole of formula 4;
• Step (iii):
• crystallizing 5-methoxy-3-[(4-methyl-1-piperazinyl) methyl]-1H-indole of formula 4 in toluene by heating the solution to 85° C.-95° C. for a period of 1 hour, followed by cooling the solution to 10° C.-15° C. for the period of 3 hours;
• Step (iv):
• recrystallizing 5-methoxy-3-[(4-methyl-1-piperazinyl) methyl]-1H-indole of formula 4 in toluene by heating the solution to 95° C.-105° C. for a period of 2 hours, followed by cooling the solution to 10° C. 15° C. for a period of 3 hours;
• Step (v):
• reacting the above obtained crystalline 5-methoxy-3-[(4-methyl-1-piperazinyl) methyl]-1H-indole of formula 4 with 2-bromobenzenesulfonyl chloride of formula 5;
• in presence of tetrahydrofuran and potassium hydroxide at a temperature in the range of 20° C. to 40° C. for a period of 3.5 hours to 4.5 hours to obtain 1-[(2-bromophenyl)sulfonyl]-5-methoxy-3-[(4-methyl-1-piperazinyl)methyl]-1H-indole of formula 6;
• Step (vi):
• converting 1-[(2-bromophenyl)sulfonyl]-5-methoxy-3[(4-methyl-1-piperazinyl)methyl]-1H-indole of formula 6 in presence of ethanol and methanesulfonic acid at a temperature in the range of 15° C. to 35° C. for a period of 18 hours to 24 hours to obtain 1-[(2-bromophenyl)sulfonyl]-5-methoxy-3-[(4-methyl-1-piperazinyl)methyl]-1H-indole dimesylate of formula 7;
• Step (vii):
• converting 1-[(2-bromophenyl)sulfonyl]-5-methoxy-3-[(4-methyl-1-piperazinyl)methyl]-1H-indole dimesylate of formula 7 in presence of aqueous ethanol and carbon slurry at a temperature in the range of 75° C. to 85° C. for a period of 0.5 hour-1.5 hours to obtain 1-[(2-bromophenyl)sulfonyl]-5-methoxy-3-[(4-methyl-1-piperazinyl)methyl]-1H-indole dimesylate monohydrate of formula (I).