methyl 4-(3-bromophenyl)-2,4-dioxobutanoate

Conditions: temp:65.01; pressure:0.00; stir:; See reaction.notes.procedure_details.

Procedure: 3.00 g (10.52 mmol) of 4-(3-bromo-phenyl)-2,4-dioxo-butyric acid methyl ester were suspended in 16 ml of EtOH and 0.485 g (10.52 mmol) of methylhydrazine were added. The reaction was heated under reflux (65° C.) for 5 h. Then the solvent was evaporated and the residue was partitioned between aqueous 1N HCl/EtOAc (3×). The organic phases were washed with aqueous sat. NaCl, dried (Na2SO4) and evaporated. The crude product was purified by flash chromatography (SiO2, n-heptane/EtOAc 99:1) to give 1.64 g (37%) of 5-(3-bromo-phenyl)-2-methyl-2H-pyrazole-3-carboxylic acid methyl ester (and ethyl ester) as white powder (MS: methyl ester 295.1 MH+, 1 Br; ethyl ester 309.1 MH+, 1 Br) and 1.11 g (28%) of 5-(3-bromo-phenyl)-1-methyl-1H-pyrazole-3-carboxylic acid methyl ester (and ethyl ester) as yellow oil (MS: methyl ester 295.1 MH+, 1 Br; ethyl ester 309.1 MH+, 1 Br). The reaction was heated Then the solvent was evaporated the residue was partitioned between aqueous 1N HCl/EtOAc (3×) The organic phases were washed with aqueous sat. NaCl dried (Na2SO4) evaporated The crude product was purified by flash chromatography (SiO2, n-heptane/EtOAc 99:1)

Conditions: temp:65.01; pressure:0.00; stir:; See reaction.notes.procedure_details.

Procedure: 3.00 g (10.52 mmol) of 4-(3-bromo-phenyl)-2,4-dioxo-butyric acid methyl ester were suspended in 16 ml of EtOH and 0.485 g (10.52 mmol) of methylhydrazine were added. The reaction was heated under reflux (65° C.) for 5 h. Then the solvent was evaporated and the residue was partitioned between aqueous 1N HCl/EtOAc (3×). The organic phases were washed with aqueous sat. NaCl, dried (Na2SO4) and evaporated. The crude product was purified by flash chromatography (SiO2, n-heptane/EtOAc 99:1) to give 1.64 g (37%) of 5-(3-bromo-phenyl)-2-methyl-2H-pyrazole-3-carboxylic acid methyl ester (and ethyl ester) as white powder (MS: methyl ester 295.1 MH+, 1 Br; ethyl ester 309.1 MH+, 1 Br) and 1.11 g (28%) of 5-(3-bromo-phenyl)-1-methyl-1H-pyrazole-3-carboxylic acid methyl ester (and ethyl ester) as yellow oil (MS: methyl ester 295.1 MH+, 1 Br; ethyl ester 309.1 MH+, 1 Br). The reaction was heated Then the solvent was evaporated the residue was partitioned between aqueous 1N HCl/EtOAc (3×) The organic phases were washed with aqueous sat. NaCl dried (Na2SO4) evaporated The crude product was purified by flash chromatography (SiO2, n-heptane/EtOAc 99:1)

Conditions: temp:0.00; pressure:0.00; stir:; See reaction.notes.procedure_details.

Procedure: To a suspension of 2,4-dioxo-4-(3-bromophenyl)-butyric acid methyl ester (10.3 g, 36.1 mmol) in anhydrous MeOH (100 mL) was added hydroxylamine hydrochloride (3.8 g, 54.2 mmol). The mixture was then refluxed for 90 min. The reaction mixture was then cooled to room temperature, and ice/water mixture (200 mL) was added. The mixture was stirred for 20 minutes, filtered through a Buchner funnel and washed with cold water. The light yellow solid was dried in vacuum oven to provide the title compound (8.9 g, 87% yield). The mixture was then refluxed for 90 min filtered through a Buchner funnel washed with cold water The light yellow solid was dried in vacuum oven

Conditions: temp:65.01; pressure:0.00; stir:; See reaction.notes.procedure_details.

Procedure: 3.00 g (10.52 mmol) of 4-(3-bromo-phenyl)-2,4-dioxo-butyric acid methyl ester were suspended in 16 ml of EtOH and 0.485 g (10.52 mmol) of methylhydrazine were added. The reaction was heated under reflux (65° C.) for 5 h. Then the solvent was evaporated and the residue was partitioned between aqueous 1N HCl/EtOAc (3×). The organic phases were washed with aqueous sat. NaCl, dried (Na2SO4) and evaporated. The crude product was purified by flash chromatography (SiO2, n-heptane/EtOAc 99:1) to give 1.64 g (37%) of 5-(3-bromo-phenyl)-2-methyl-2H-pyrazole-3-carboxylic acid methyl ester (and ethyl ester) as white powder (MS: methyl ester 295.1 MH+, 1 Br; ethyl ester 309.1 MH+, 1 Br) and 1.11 g (28%) of 5-(3-bromo-phenyl)-1-methyl-1H-pyrazole-3-carboxylic acid methyl ester (and ethyl ester) as yellow oil (MS: methyl ester 295.1 MH+, 1 Br; ethyl ester 309.1 MH+, 1 Br). The reaction was heated Then the solvent was evaporated the residue was partitioned between aqueous 1N HCl/EtOAc (3×) The organic phases were washed with aqueous sat. NaCl dried (Na2SO4) evaporated The crude product was purified by flash chromatography (SiO2, n-heptane/EtOAc 99:1)