ditert-butyl oxalate

Conditions: temp:0.00; pressure:0.00; stir:

Conditions: temp:0.00; pressure:0.00; stir:

Conditions: temp:0.00; pressure:0.00; stir:

Conditions: temp:0.00; pressure:0.00; stir:

Conditions: temp:0.00; pressure:0.00; stir:

Conditions: temp:-78.01; pressure:0.00; stir:; See reaction.notes.procedure_details.

Procedure: A 1-L flame-dried flask was charged with 130 mL of LiHMDS (130 mmol; 1.0 M in THF) and 410 mL of ethyl ether. The resulting solution was cooled to −78° C. and 2-acetylfuran (14 g, 12 m mmol) was added in one portion. After 5 min, di-tert-butyl oxalate was added dropwise over 1 h as a solution in 100 mL of ether. The resulting mixture was warmed to 23° C. over a period of 3 h and was maintained at rt for 20 h. The mixture was then filtered, and the resulting beige precipitate was washed with 100 mL of ether. The filter cake was dried in a vacuum oven for 1 h to afford lithium 1-tert-butoxy-4-(2-furyl)-1,4-dioxo-2-buten-2-olate (25 g, 83%) as a cream colored solid. 1H NMR (DMSO-d6) δ 7.75 (t, 1H), 6.96 (m, 1H), 6.56 (m, 1H), 3.34 (s, 2H), 1.46 (s, 9H). A 1-L flame-dried flask The resulting mixture was warmed to 23° C. over a period of 3 h was maintained at rt for 20 h The mixture was then filtered the resulting beige precipitate was washed with 100 mL of ether The filter cake was dried in a vacuum oven for 1 h

Conditions: temp:-78.01; pressure:0.00; stir:; See reaction.notes.procedure_details.

Procedure: A 1-L flame-dried flask was charged with 130 mL of LiHMDS (130 mmol; 1.0 M in THF) and 410 mL of ethyl ether. The resulting solution was cooled to −78° C. and 2-acetylfuran (14 g, 12 m mmol) was added in one portion. After 5 min, di-tert-butyl oxalate was added dropwise over 1 h as a solution in 100 mL of ether. The resulting mixture was warmed to 23° C. over a period of 3 h and was maintained at rt for 20 h. The mixture was then filtered, and the resulting beige precipitate was washed with 100 mL of ether. The filter cake was then dried in a vacuum oven for 1 h to afford lithium 1-tert-butoxy-4-(2-furyl)-1,4-dioxo-2-buten-2-olate (25 g, 83%) as a cream colored solid. 1H NMR (DMSO-d6) δ 7.75 (t, 1H), 6.96 (m, 1H), 6.56 (m, 1H), 3.34 (s, 2H), 1.46 (s, 9H). A 1-L flame-dried flask The resulting mixture was warmed to 23° C. over a period of 3 h was maintained at rt for 20 h The mixture was then filtered the resulting beige precipitate was washed with 100 mL of ether The filter cake was then dried in a vacuum oven for 1 h

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

Procedure: To a solution of the title compound of Example C (5.41 g, 22.6 mmol) in dry THF (100 ml) was added di-tert-butyl oxalate (4.57 g, 22.6 mmol), followed by potassium tert-butoxide (5.07 g, 45.2 mmol) and the resulting dark yellow solution was stirred for 84 h at room temperature. The reaction mixture was then acidified with 1N HCl to pH=3, followed by the addition of H2O (35 ml) and the mixture was then extracted with CH2Cl2. The combined organic layers were dried with MgSO4, filtered and dried to give a solid which was chromatographed on silica gel eluting with 1/1/98 MeOH/HOAc/CH2Cl2 to give the title compound (3.166 g, 48%). Anal calcd for C15H16NO4F: C, 61.43; H, 5.50; N, 4.78. Found: C, 61.16; H, 5.50; N, 4.77. the mixture was then extracted with CH2Cl2 The combined organic layers were dried with MgSO4 filtered dried to give a solid which was chromatographed on silica gel eluting with 1/1/98 MeOH/HOAc/CH2Cl2

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

Procedure: To a solution of the title compound of Example C (5.41 g, 22.6 mmol) in dry THF (100 ml) was added di-tert-butyl oxalate (4.57 g, 22.6 mmol), followed by potassium tert-butoxide (5.07 g, 45.2 mmol) and the resulting dark yellow solution was stirred for 84 h at room temperature. The reaction mixture was then acidified with 1N HCl to pH=3, followed by the addition of H2O (35 ml) and the mixture was then extracted with CH2Cl2. The combined organic layers were dried with MgSO4, filtered and dried to give a solid which was chromatographed on silica gel eluting with 1/1/98 MeOH/HOAc/CH2Cl2 to give the title compound (3.166 g, 48%). Anal calcd for C15H16NO4F: C, 61.43; H, 5.50; N, 4.78. Found: C, 61.16; H, 5.50; N, 4.77. the mixture was then extracted with CH2Cl2 The combined organic layers were dried with MgSO4 filtered dried to give a solid which was chromatographed on silica gel eluting with 1/1/98 MeOH/HOAc/CH2Cl2

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

Procedure: To a solution of the title compound of Example B (29.37 g, 0.133 mol) and di-tert-butyl oxalate (26.90 g, 0.133 mol) in dry THF (350 ml) was added potassium tert-butoxide (29.84 g, 0.266 mol) and the resulting solution was heated under reflux for 24 h. The mixture was then cooled and the solvent removed in vacuo. The resulting solid was suspended in CH2Cl2 and 1N aqueous HCl was added. The resulting suspension was filtered and the organic filtrate was dried over MgSO4 and concentrated in vacuo. The residue was then chromatographed on silica gel eluting with 1/1/98 HOAc/EtOH/CH2Cl2 to give the title compound (19.06 g, 52%) as a solid. Anal calcd for C15H17NO4 : C, 65.44; H, 6.22; N, 5.09. Found: C, 65.05; H, 6.33; N, 4.86. MS M+1 calcd for C15H17NO4 276, found 276. the resulting solution was heated under reflux for 24 h The mixture was then cooled the solvent removed in vacuo 1N aqueous HCl was added The resulting suspension was filtered the organic filtrate was dried over MgSO4 concentrated in vacuo The residue was then chromatographed on silica gel eluting with 1/1/98 HOAc/EtOH/CH2Cl2

Conditions: temp:-78.01; pressure:0.00; stir:; See reaction.notes.procedure_details.

Procedure: Under an atmosphere of nitrogen, a solution of 3′-chloroacetophenone (1.015 mL, 7.82 mmol) in anhydrous diethyl ether (50 mL) was allowed to cool to −78° C. for 15 minutes prior to the slow addition of a 1.0 M solution of LHMDS (8.60 mL, 8.60 mmol) in THF. The enolate formation was allowed to stir for 45 minutes at −78° C., after which di-tert-butyl oxalate (1.898 g, 9.38 mmol) was added as a single portion. The pale yellow reaction mixture was allowed to warm to RT and stir for 18 hours. The dark-green solution was then quenched with 50 mL of a 1.0 M aq. solution of HCl. The two layers were separated and the aq. layer was extracted twice more with EtOAc. The combined organic layers were washed with brine, dried over anhydrous MgSO4, filtered and the filtrate concentrated under reduced pressure to afford an orange oil. The crude reaction mixture was purified by silica gel chromatography (40 g REDISEP® column, eluting with a gradient from 100% hexanes to 80:20 hexanes:EtOAc solution). Fractions containing the product were combined and evaporated to afford Intermediate A129A (2.17 g, 98%) as a yellow solid. 1H NMR (400 MHz, chloroform-d) δ ppm 7.94-7.99 (1H, m), 7.86 (1H, dt, J=7.78, 1.38 Hz), 7.58 (1H, ddd, J=7.97, 2.20, 1.13 Hz), 7.43-7.49 (1H, m), 6.94-6.99 (1H, m), 1.58-1.63 (9H, m). to warm to RT stir for 18 hours The dark-green solution was then quenched with 50 mL of a 1.0 M aq. solution of HCl The two layers were separated the aq. layer was extracted twice more with EtOAc The combined organic layers were washed with brine dried over anhydrous MgSO4 filtered the filtrate concentrated under reduced pressure to afford an orange oil The crude reaction mixture was purified by silica gel chromatography (40 g REDISEP® column eluting with a gradient from 100% hexanes to 80:20 hexanes Fractions containing the product evaporated to afford Intermediate A129A (2.17 g, 98%) as a yellow solid

Conditions: temp:-78.01; pressure:0.00; stir:; See reaction.notes.procedure_details.

Procedure: Part A. A 1-L flame-dried flask was charged with 130 mL of LiHMDS (130 mmol; 1.0 M in THF) and 410 mL of ethyl ether. The resulting solution was cooled to −78° C. and 2-acetylfuran (14 g, 12 m mmol) was added in one portion. After 5 min, di-tert-butyl oxalate was added dropwise over 1 h as a solution in 100 mL of ether. The resulting mixture was warmed to 23° C. over a period of 3 h and was maintained at rt for 20 h. The mixture was then filtered, and the resulting beige precipitate was washed with 100 mL of ether. The filter cake was dried in a vacuum oven for 1 h to afford lithium 1-tert-butoxy-4-(2-furyl)-1,4-dioxo-2-buten-2-olate (25 g, 83%) as a cream colored solid. 1H NMR (DMSO-d6) δ 7.75 (t, 1H), 6.96 (m, 1H), 6.56 (m, 1H), 3.34 (s, 2H), 1.46 (s, 9H). Part B. To the product (1.0 g, 4.6 mmol) from Part A was added 4-methoxyphenylhydrazine hydrochloride (480 mg, 2.8 mmol) and glacial acetic acid (15 mL). The resulting orange mixture was warmed to 40° C. and was then cooled to rt after 1.5 h. The reaction was poured into saturated aqueous sodium bicarbonate (100 mL), and the aqueous layer was washed with ethyl acetate (3×50 mL). The combined organic layers were washed with saturated aqueous sodium chloride, dried over sodium sulfate, and concentrated to dryness. The resulting red-black residue was recrystallized from hexanes to afford tert-butyl 5-(2-furyl)-1-(4-methoxyphenyl)-1H-pyrazole-3-carboxylate (870 mg, 93%) as a yellow-orange solid. 1H NMR (CDCl3) δ 7.40(br s, 1H), 7.35 (d, 2H), 7.07 (s, 1H), 6.96 (d, 2H), 6.30 (m, 1H), 5.86 (d, 9H), 3.86 (s, 3H), 1.62 (s, 9H). Part C. To tert-butyl 5-(2-furyl)-1-(4-methoxyphenyl)-1H-pyrazole-3-carboxylate (1.0 g, 3.0 mmol) was added dichloromethane (7 mL) and trifluoroacetic acid (7 mL). The resulting black solution was maintained at rt under nitrogen for 2 h and was then concentrated to dryness. The resulting mixture was triturated with chloroform, and the remaining solid was washed with 50% hexanes in chloroform to afford 5-(2-furyl)-1-(4-methoxyphenyl)-1H-pyrazole-3-carboxylic acid (800 mg, 96%) as a light brown solid. 1H NMR (d6-DMSO) δ 7.75 (b m, 1H), 7.41 (d, 2H), 7.10 (d, 2H), 7.09 (s, 1H), 6.51 (br m, 1H), 6.09 (d, 1H), 3.84 (s, 3H). Part D. To the product (800 mg, 2.8 mmol) from Part C was added dichloromethane (50 mL) and 2.0 M oxalyl chloride (2.1 mL, 4.2 mmol) in dichloromethane. After dropwise addition of N,N-dimethylformamide (2 drops) to the brown mixture, gas evolved and the mixture became clear over a period of 30 min. The brown solution was concentrated; the resulting residue was redissolved in dichloromethane (50 mL), and 0.5 M ammonia in dioxane (23 mL, 11 mmol) was added via cannula. After 30 min, the resulting beige suspension was poured into water (80 mL). The aqueous layer was washed with dichloromethane (3×50 mL), and the combined organic layers were dried over sodium sulfate and concentrated to afford 5-(2-furyl)-1-(4-methoxyphenyl)-1H-pyrazole-3-carboxamide (650 mg, 82%) as a beige solid. LC/MS (ESI+): 284.1 (M+H)+. 1H NMR (CD3OD) δ 7.52(s, 1H), 7.35 (d, 2H), 7.07 (s, 1H), 7.05 (d, 2H), 6.39 (br m, 1H), 5.96 (d, 1H), 4.88 (s, 3H). Part E. To 5-(2-furyl)-1-(4-methoxyphenyl)-1H-pyrazole-3-carboxamide (2.0 g, 6.6 mmol) was added pyridine (1.6 mL, 20 mmol) and dioxane (66 mL). Trifluoroacetic anhydride (1.9 mL, 13 mmol) was added dropwise over 2 min, and the resulting suspension was stirred for 40 min. The now clear red solution was poured into water (70 mL) and ethyl acetate (70 mL). The layers were separated, and the organic layer was washed with 1N aqueous hydrochloric acid (2×50 mL), saturated aqueous sodium chloride, and dried over sodium sulfate. The organic layers were concentrated, and the resulting residue was purified by radial chromatography (20–80% ethyl acetate in hexanes) to afford 5-(2-furyl)-1-(4-methoxyphenyl)-1H-pyrazole-3-carbonitrile (1.4 g, 74%) as an orange solid. LC/MS (ESI+): 266.0 (M+H)+. 1H NMR (CDCl3) δ 7.44 (br m, 1H), 7.34 (d, 2H), 7.01 (s, 1H), 7.00 (d, 2H), 6.34 (m, 1H), 5.92 (d, 1H), 3.85(s, 3H). Part F. To the product (1.4 g, 4.9 mmol) from Part E was added water (30 mL), 5% aqueous sodium dihydrogenphosphate (21 mL), and tert-butanol (30 mL). The resulting mixture was warmed to 60° C., and potassium permanganate (4.7 g, 29 mmol) was added over a period of 5 min. After an additional 5 min, the resulting purple slurry was cooled to 0° C., and the reaction was quenched by the addition of 50 mL of saturated aqueous sodium bisulfite. The resulting brown mixture was filtered, washed with 100 mL of water, and the filtrate was acidified with 6N aqueous hydrogen chloride. The resulting mixture was filtered to afford 3-cyano-1-(4-methoxyphenyl)-1H-pyrazole-5-carboxylic acid (300 mg, 25%) as a yellow solid. Extraction of the aqueous layer with ethyl acetate (2×50 mL) afforded an additional 215 mg (18%) of impure 3-cyano-1-(4-methoxyphenyl)-1H-pyrazole-5-carboxylic acid as a yellow oil. LC/MS (ESI+): 244.1 (M+H)+. 1H NMR (precipitate) (CDCl3) δ 7.42 (s, 1H), 7.35 (d, 2H), 6.98 (d, 2H), 3.87 (s, 3H). Part G. To a stirring solution of trimethylacetyl chloride (0.087 mL, 0.70 mmol), triethylamine (0.290 mL, 2.1 mmol), and diethyl ether (14 mL) in a flame-dried flask was added 3-cyano-1-(4-methoxyphenyl)-1H-pyrazole-5-carboxylic acid (170 mg, 0.70 mmol). The resulting white slurry was warmed to 23° C. and stirred for 1.5 h. The mixture was filtered, and the filtrate was concentrated. The resulting residue was partially redissolved in diethyl ether (15 mL) and again filtered. The filtrate was concentrated to give 3-cyano-1-(4-methoxyphenyl)-1H-pyrazole-5-carboxylic 2,2-dimethylpropanoic anhydride as a viscous oil. A 1-L flame-dried flask The resulting mixture was warmed to 23° C. over a period of 3 h was maintained at rt for 20 h The mixture was then filtered the resulting beige precipitate was washed with 100 mL of ether The filter cake was dried in a vacuum oven for 1 h