3-Bromo-4-hydrazino-benzoic acid methyl ester synthesis

Yield:-

Reaction Conditions:

Stage #1: methyl 4-amino-3-bromobenzoatewith hydrogenchloride;sodium nitrite in water at -10 - -5; for 0.666667 h;
Stage #2: with hydrogenchloride;water;tin(ll) chloride at -10 - 20; for 1.5 h;
Stage #3: with sodium hydroxide in water at 20; pH=12;

Steps:

H-2

H-2) methyl 3-bromo-4-hydrazino-benzoate; Methyl-4-amino-3-bromobenzoate (32 g, 139 mmol) is combined with 250 mL conc. hydrochloric acid and cooled to -10° C. A solution of sodium nitrite (10.2 g, 146 mmol) in 120 mL water is added dropwise such that the temperature does not exceed -5° C. After 40 min stirring at -10° C. a solution of tin(II)chloride dihydrate (128 g, 556 mmol) in 130 mL conc. hydrochloric acid is added dropwise to the suspension, while the reaction temperature does not exceed -5° C. The thick liquid suspension is stirred for 1.5 h at RT, before being adjusted to pH 10 with NaOH (12 N). The reaction mixture is combined with 500 mL dichloromethane and water and after 30 min stirring it is filtered. The filter cake is combined with 300 mL dichloromethane and 100 mL water and refluxed for 30 min. After filtration the filtrate is extracted with chloroform. The combined organic phases are dried on magnesium sulphate, filtered and evaporated to dryness. Yield: 34 g.

References:

US2007/270401,2007,A1 Location in patent:Page/Page column 6