| 64.5% |
Stage #1: at 20 - 120℃;
Stage #2: With sodium hydroxide In water at 20℃; for 4 h;
Stage #3: With hydrogenchloride In water |
Preparation 11: 3-[(3-Chloropropyl)thio]-4-methyl-5-(4-methyl-1,3-oxazol-5-yl)-4H- 1,2,4-triazole Ethyl-2-chloroacetoacetate (1 wt; 1 eq. , 1000 g) was aged with formamide (0.68 vol; ca. 2.8 eq. ) and the resulting solution was heated to 120 °C. After 5 hours the mixture was allowed to cool to room temperature and allowed to age under nitrogen over night. The mixture was treated with NaOH (3 M, 6 vol, reaction moderately exothermic) and stirred at room temperature for 4 hours. Ethyl acetate (6 vol) was added and the phases allowed to separae. The organic layer was discarded while the aqueous was acidified with conc. (32percent) aqueous HCI to pH 2 (ca. 2.0 vol). A precipitate started to form. The suspension was treated with AcOEt (8 vol) and vigorously stirred until the bulk of the precipitate had dissolved. The aqueous phase was further extracted with AcOEt twice (6 vol each) and the combined organic layers distilled to low volume (again a suspension was observed at low volume). Fresh AcOEt (8 vol) was added and the mixture evaporated to dryness. The collected solid was placed in the oven at 40 °C over night under reduced pressure to give 4-methyl-1,3-oxazole-5-carboxylic acid (498 g, 64.5percent). This material (498 g, 1 wt) was dissolved in dry tetrahydrofuran (5 vol), under nitrogen, cooled to 0 °C. DCC (1.62 wt, 1 eq) was added portionwise followed by HOBt (1.07 wt, 1 eq). The mixture was warmed to 25No.2 °C and stirred for 30 min. 4-Methyl-3-thiosemicarbazide (0.83 wt, 1 eq) was then added and the mixture further stirred for 2 h at 25No.2°C. The mixture was filtered and the cake was washed with fresh tetrahydrofuran (1 vol) and dried on the filter for a few hours. The cake was suspended in 1 M aqueous NaOH (13 vol) and heated to 70 °C for 30 min. After this time, the mixture was cooled to 25No.2 °C and a solid was removed by filtration. The cake was washed with 1 M aqueous NaOH (10 vol). The combined mother liquors were cooled to 0 °C and acidified to ca. pH 5 with HCI (aqueous, 16percent; NOTE: keep temperature while adding HCI below +10 °C). The suspended product was isolated by filtration washing with water (2x3 vol). The cake was dried at 40 °C for 18 h in high vacuum to obtain 4-methyl-5-(4-methyl-1,3-oxazol-5-yl)-2,4-dihydro-3H-1,2,4-triazole-3- thione (respectively a tautomeric form thereof; 290 g, 37percent). NaOEt (21percent solution in EtOH, 2.08 vol, 1.1 eq) was added to EtOH (20 vol) under nitrogen atmosphere. 4-Methyl- 5-(4-methyl-1,3-oxazol-5-yl)-2,4-dihydro-3H-1,2,4-triazole-3-thione (respectively a tautomeric form thereof; 290 g, 1 wt) was added in one portion and the resulting mixture stirred at 25No.2°C until a clear solution was obtained. Then 1-bromo-3-chloropropane (0.54 vol, 1.1 eq) was added and the solution stirred at 40 'C for 24 h then cooled to 25 'C. After filtration water (20 vol) was added and the ethanolic phase was removed by vacuum distillation (internal temperature -40 'C). The mixture was extracted with EtOAc (41 vol). The aqueous layer was removed and the organic phase was evaporated to dryness. Dichloromethane (4 vol) was added. The organic solution is purified through a short silica gel column (18 wt of silica), eluting with EtOAc (200 vol) to give the title compound as a solid foam (267.64 g, 66percent). NMR ('H, CDC13): No. 7.90 (s, 1 H), 3.70 (s, 5H), 3.40 (t, 2H), 2.52 (s, 3H), 2.30 (m, 2H). MS (m/z): 273 [MH]+. |
| 64.5% |
Stage #1: at 20 - 120℃;
Stage #2: With sodium hydroxide In water at 20℃; for 4 h;
Stage #3: With hydrogenchloride In water |
Preparation 7: 3-[(3-Chloropropyl)thio]-4-methyl-5-(4-methyl-1 ,3-oxazol-5-yl)-4H- 1 ,2,4-triazole; EPO <DP n="36"/>Ethyl^-chloroacetoacetate (1 wt; 1 eq., 1000 g) was aged with formamide (0.68 vol; ca. 2.8 eq.) and the resulting solution was heated to 120 0C. After 5 hours the mixture was allowed to cool to room temperature and allowed to age under nitrogen over night. The mixture was treated with NaOH (3 M, 6 vol, reaction moderately exothermic) and stirred at room temperature for 4 hours. Ethyl acetate (6 vol) was added and the phases allowed to separae. The organic layer was discarded while the aqueous was acidified with cone. (32percent) aqueous HCI to pH 2 {ca. 2.0 vol). A precipitate started to form. The suspension was treated with AcOEt (8 vol) and vigorously stirred until the bulk of the precipitate had dissolved. The aqueous phase was further extracted with AcOEt twice (6 vol each) and the combined organic layers distilled to low volume (again a suspension was observed at low volume). Fresh AcOEt (8 vol) was added and the mixture evaporated to dryness. The collected solid was placed in the oven at 40 0C over night under reduced pressure to give 4-methyl-1 ,3-oxazole-5-carboxylic acid (498 g, 64.5percent). This material (498 g, 1 wt) was dissolved in dry tetrahydrofuran (5 vol), under nitrogen, cooled to 0 0C. DCC (1.62 wt, 1 eq) was added portionwise followed by HOBt (1.07 wt, 1 eq). The mixture was warmed to 25+/-2 0C and stirred for 30 min. 4-Methyl-3- thiosemicarbazide (0.83 wt, 1 eq) was then added and the mixture further stirred for 2 h at 25+/-2°C. The mixture was filtered and the cake was washed with fresh tetrahydrofuran (1 vol) and dried on the filter for a few hours. The cake was suspended in 1 M aqueous NaOH (13 vol) and heated to 70 0C for 30 min. After this time, the mixture was cooled to 25+/-2 °C and a solid was removed by filtration. The cake was washed with 1 M aqueous NaOH (10 vol). The combined mother liquors were cooled to 0 0C and acidified to ca. pH 5 with HCI (aqueous, 16percent; NOTE: keep temperature while adding HCI below +10 0C). The suspended product was isolated by filtration washing with water (2x3 vol). The cake was dried at 40 0C for 18 h in high vacuum to obtain 4-methyl-5-(4-methyl-1 ,3-oxazol-5- yl)-2,4-dihydro-3H-1 ,2,4-triazole-3-thione (respectively a tautomeric form thereof; 290 g, 37percent). NaOEt (21percent solution in EtOH, 2.08 vol, 1.1 eq) was added to EtOH (20 vol) under nitrogen atmosphere. 4-Methyl-5-(4-methyl-1 ,3-oxazol-5-yl)-2,4-dihydro-3H-1 ,2,4-triazole- 3-thione (respectively a tautomeric form thereof; 290 g, 1 wt) was added in one portion and the resulting mixture stirred at 25+/-2°C until a clear solution was obtained. Then 1- bromo-3-chloropropane (0.54 vol, 1.1 eq) was added and the solution stirred at 40 'C for 24 h then cooled to 25 'C. After filtration water (20 vol) was added and the ethanolic phase was removed by vacuum distillation (internal temperature ~40 'C). The mixture was extracted with EtOAc (41 vol). The aqueous layer was removed and the organic phase was evaporated to dryness. Dichloromethane (4 vol) was added. The organic solution is purified through a short silica gel column (18 wt of silica), eluting with EtOAc (200 vol) to give the title compound as a solid foam (267.64 g, 66percent). NMR (1H1 CDCI3): δ 7.90 (s, 1H), 3.70 (s, 5H), 3.40 (t, 2H), 2.52 (s, 3H), 2.30 (m, 2H). |
| 44% |
Stage #1: at 20 - 120℃; Inert atmosphere
Stage #2: at 20℃; for 4 h; Inert atmosphere
Stage #3: With hydrogenchloride In waterInert atmosphere |
A stirred mixture of ethyl 2-chloro-3-oxobutanoate (16.8 ml, 121.51 mmol) and formamide (13.5 mL, 340.23 mmol) was heated to 120 °C. After 6 hrs the mixture was allowed to cool to RT and stirred under nitrogen O/N. The mixture was treated with 3M NaOH (120 mL, reaction moderately exothermic) and stirred at RT for 4 hours. EtOAc (120 mL) was added and the phases allowed separating. The organic layer was discarded while the aqueous was acidified with 37percent aqueous HCI to pH 2 (~ 40 mL). A precipitate started to form. The suspension was treated with EtOAc (160 mL) and, vigorously shaken until the precipitate had dissolved. Phases were separated and the aqueous one was further extracted with EtOAc twice (120 mL). The combined organic layers were concentrated to low volume. Fresh EtOAc (160 mL) was added and the mixture evaporated to dryness under vacuum. The collected solid was placed in the oven at 45 °C O/N under reduced pressure affording 4-methyl-1 ,3- oxazole-5-carboxylic acid (p53, 8.52 g, y=44percent) as rusty brown solid. MS (/T7/z): 128.0 [MH]+ |
| 44% |
Stage #1: at 120℃; for 6 h; Inert atmosphere
Stage #2: at 20℃; for 4 h; |
A stirred mixture of ethyl 2-chloro-3-oxobutanoate (16.8 mL, 121.51 mmol) and formamide (13.5 mL, 340.23 mmol) was heated to 120 °C. After 6 hrs the mixture was allowed to cool to RT and stirred under nitrogen ON. The mixture was treated with 3 M NaOH (120 mL, reaction moderately exothermic) and stirred at RT for 4 hrs. EtOAc (120 mL) was added and the phases allowed separating. The organic layer was discarded while the aqueous was acidified with37percent aqueous HCI to pH 2 (4O mL). A precipitate started to form. The suspension was treated with EtOAc (160 mL) and, vigorously shaken. Phases were separated and the aqueous one was further extracted with EtOAc twice (120 mL). The combined organic layers were concentrated to low volume. Fresh EtOAc (160 mL) was added and the mixture evaporated to dryness under vacuum. The collected solid was placed in the oven at 45 °C ON under reduced pressure to give8.52 g of title compound (p1, y= 44percent), rusty brown solid. MS (m/z): 128.0 [IVII{]t |
| 44% |
Stage #1: at 120℃; for 6 h;
Stage #2: at 20℃; for 4 h; Inert atmosphere |
Preparation 1
4-methyl-1,3-oxazole-5-carboxylic acid
A stirred mixture of ethyl 2-chloro-3-oxobutanoate (16.8 mL, 121.51 mmol) and formamide (13.5 mL, 340.23 mmol) was heated to 120° C.
After 6 hrs the mixture was allowed to cool to RT and stirred under nitrogen O/N.
The mixture was treated with 3 M NaOH (120 mL, reaction moderately exothermic) and stirred at RT for 4 hrs. EtOAc (120 mL) was added and the phases allowed separating.
The organic layer was discarded while the aqueous was acidified with 37percent aqueous HCl to pH 2 (˜40 mL).
A precipitate started to form.
The suspension was treated with EtOAc (160 mL) and, vigorously shaken.
Phases were separated and the aqueous one was further extracted with EtOAc twice (120 mL).
The combined organic layers were concentrated to low volume.
Fresh EtOAc (160 mL) was added and the mixture evaporated to dryness under vacuum. |
| 35.3% |
Stage #1: at 120℃; for 21 h;
Stage #2: With sodium hydroxide; water In tert-butyl methyl ether; N,N-dimethyl-formamide at 20℃; for 3 h;
Stage #3: With hydrogenchloride In water at 20℃; for 2.16667 h; |
Ethyl^-chloroacetoacetate (28.6 g, 24.0 ml.) was dissolved in DMF (28.6 ml_) and formamide (19.5 mL) was added. The resulting solution was heated up to 120 0C (internal temperature) under nitrogen for 21 h. The mixture was allowed to cool down to 200C, diluted with ter-butyl methyl ether (172 mL) and washed with water (115 mL). The aqueous phase was extracted again with 115 mL of fert-butyl methyl ether and the combined organic layers were washed twice with water (86 mL) and treated with NaOH 3 N (86 mL). The resulting mixture was stirred at 200C for 3 hours. The organic layer was discarded while the aqueous was acidified with 20 mL of concentrated HCI (37percent sol.) till pH 2 over 10 minutes. A precipitate started to crush out of solution. The suspension was stirred at 200C for 2 h, filtered and the cake washed with 14.3 mL of cold water (1O0C ca.). The collected solid was dried under high vacuum at 400C for 16 hours. The title compound was obtained in a theoretical yield of 35.3 percent (7.81 g). NMR (1 H, DMSO-d6, δ ppm): 13.5 (bs, 1 H), 8.47 (s, 1 H), 2.38 (s, 3H) MS (m/z): 128[MH]+ |
| 35.5% |
Stage #1: at 120℃; for 21 h;
Stage #2: With sodium hydroxide In water; N,N-dimethyl-formamide at 20℃; for 3 h;
Stage #3: With hydrogenchloride In water; N,N-dimethyl-formamide at 20℃; for 2.16667 h; |
Ethyl^-chloroacetoacetate (28.6 g, 24.0 ml.) was dissolved in DMF (28.6 mL) and formamide (19.5 mL) was added. The resulting solution was heated up to 120 0C (internal temperature) under nitrogen for 21 h. The mixture was allowed to cool down to 200C, diluted with ter-butyl methyl ether (172 mL) and washed with water (115 mL). The aqueous phase was extracted again with 115 mL of tert-butyl methyl ether and the combined organic layers were washed twice with water (86 mL) and treated with NaOH 3 N (86 mL). The resulting mixture was stirred at 200C for 3 hours. The organic layer was discarded while the aqueous was acidified with 20 mL of concentrated HCI (37percent sol.) till pH 2 over 10 minutes. A precipitate started to crush out of solution. The suspension was stirred at 200C for 2 h, filtered and the cake washed with 14.3 mL of cold water (1O0C ca.). The collected solid was dried under high vacuum at 400C for 16 hours. The title compound was obtained in a theoretical yield of 35.5 percent (7.8 g). |
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