ethyl 5-formyl-1H-pyrrole-2-carboxylate

Conditions: temp:90.01; pressure:0.00; stir:; See reaction.notes.procedure_details.

Procedure: A mixture of 5-formyl-1H-pyrrole-2-carboxylic acid ethyl ester (as prepared in the previous step, 300 mg, 1.80 mmol), hydroxylamine hydrochloride (560 mg, 8.10 mmol), ethanol (10 mL), sodium acetate (1.10 g, 13.4 mmol) and water (10 mL) was stirred at 90° C. for 30 min. The solvents were removed in vacuo and the solid was collected on a Buchner funnel and washed with water (10 mL) to yield 226 mg (69%) of the title compound as a white solid: LC-MS (ESI, m/z): Calcd. for C8H11N2O3, 183.1 (M+H); found: 183.0. The solvents were removed in vacuo the solid was collected on a Buchner funnel washed with water (10 mL)

Conditions: temp:-10.01; pressure:0.00; stir:; See reaction.notes.procedure_details.

Procedure: To DMF (1.3 mL, 17 mmol) cooled to 5-10° C. was added phosphorous oxychloride (1.5 mL) dropwise and the mixture was diluted with 1,2-dichloroethane (5 mL). The flask was then cooled to −10° C. and ethyl pyrrole-2-carboxylate (2.00 g, 14.4 mmol) in 1,2-dichloroethane (5 mL) was added dropwise over 5 min. The mixture was heated to reflux for 15 min, cooled to RT and ethyl acetate (15 mL), water (20 mL), and satd aq sodium bicarbonate (70 mL) were added. The layers were separated and the aqueous layer was extracted with diethyl ether (3×20 mL). The combined organic layers were washed with saturated sodium carbonate (50 mL), dried (Na2SO4) and the solvents were removed in vacuo. The resulting solid was purified by column chromatography on silica gel (300 g), eluting with 30% ethyl acetate in hexane to yield 1.0 g (42%) of the title compound as a pale yellow crystalline solid. 1H-NMR (400 MHz, CDCl3): δ 9.89 (br s, 1H), 9.67 (s, 1H), 6.95 (d, 1H, J=4.1 Hz), 6.94 (d, 1H, J=4.1 Hz), 4.38 (q, 2H, J=7.1 Hz), 1.39 (t, 3H, J=7.1). The mixture was heated to reflux for 15 min cooled to RT were added The layers were separated the aqueous layer was extracted with diethyl ether (3×20 mL) The combined organic layers were washed with saturated sodium carbonate (50 mL) dried (Na2SO4) the solvents were removed in vacuo The resulting solid was purified by column chromatography on silica gel (300 g) eluting with 30% ethyl acetate in hexane

Conditions: temp:90.01; pressure:0.00; stir:; See reaction.notes.procedure_details.

Procedure: A mixture of 5-formyl-1H-pyrrole-2-carboxylic acid ethyl ester (as prepared in the previous step, 300 mg, 1.80 mmol), hydroxylamine hydrochloride (560 mg, 8.10 mmol), ethanol (10 mL), sodium acetate (1.10 g, 13.4 mmol) and water (10 mL) was stirred at 90° C. for 30 min. The solvents were removed in vacuo and the solid was collected on a Buchner funnel and washed with water (10 mL) to yield 226 mg (69%) of the title compound as a white solid: LC-MS (ESI, m/z): Calcd. for C8H11N2O3, 183.1 (M+H); found: 183.0. The solvents were removed in vacuo the solid was collected on a Buchner funnel washed with water (10 mL)

Conditions: temp:-10.01; pressure:0.00; stir:; See reaction.notes.procedure_details.

Procedure: To DMF (1.3 mL, 17 mmol) cooled to 5-10° C. was added phosphorous oxychloride (1.5 mL) dropwise and the mixture was diluted with 1,2-dichloroethane (5 mL). The flask was then cooled to −10° C. and ethyl pyrrole-2-carboxylate (2.00 g, 14.4 mmol) in 1,2-dichloroethane (5 mL) was added dropwise over 5 min. The mixture was heated to reflux for 15 min, cooled to RT and ethyl acetate (15 mL), water (20 mL), and satd aq sodium bicarbonate (70 mL) were added. The layers were separated and the aqueous layer was extracted with diethyl ether (3×20 mL). The combined organic layers were washed with saturated sodium carbonate (50 mL), dried (Na2SO4) and the solvents were removed in vacuo. The resulting solid was purified by column chromatography on silica gel (300 g), eluting with 30% ethyl acetate in hexane to yield 1.0 g (42%) of the title compound as a pale yellow crystalline solid. 1H-NMR (400 MHz, CDCl3): δ 9.89 (br s, 1H), 9.67 (s, 1H), 6.95 (d, 1H, J=4.1 Hz), 6.94 (d, 1H, J=4.1 Hz), 4.38 (q, 2H, J=7.1 Hz), 1.39 (t, 3H, J=7.1). The mixture was heated to reflux for 15 min cooled to RT were added The layers were separated the aqueous layer was extracted with diethyl ether (3×20 mL) The combined organic layers were washed with saturated sodium carbonate (50 mL) dried (Na2SO4) the solvents were removed in vacuo The resulting solid was purified by column chromatography on silica gel (300 g) eluting with 30% ethyl acetate in hexane

Conditions: temp:90.01; pressure:0.00; stir:; See reaction.notes.procedure_details.

Procedure: A mixture of 5-formyl-1H-pyrrole-2-carboxylic acid ethyl ester (as prepared in the previous step, 300 mg, 1.80 mmol), hydroxylamine hydrochloride (560 mg, 8.10 mmol), ethanol (10 mL), sodium acetate (1.10 g, 13.4 mmol) and water (10 mL) was stirred at 90° C. for 30 min. The solvents were removed in vacuo and the solid was collected on a Buchner funnel and washed with water (10 mL) to yield 226 mg (69%) of the title compound as a white solid: LC-MS (ESI, m/z): Calcd. for C8H11N2O3, 183.1 (M+H); found: 183.0. The solvents were removed in vacuo the solid was collected on a Buchner funnel washed with water (10 mL)

Conditions: temp:-10.01; pressure:0.00; stir:; See reaction.notes.procedure_details.

Procedure: To DMF (1.3 mL, 17 mmol) cooled to 5-10° C. was added phosphorous oxychloride (1.5 mL) dropwise and the mixture was diluted with 1,2-dichloroethane (5 mL). The flask was then cooled to −10° C. and ethyl pyrrole-2-carboxylate (2.00 g, 14.4 mmol) in 1,2-dichloroethane (5 mL) was added dropwise over 5 min. The mixture was heated to reflux for 15 min, cooled to RT and ethyl acetate (15 mL), water (20 mL), and satd aq sodium bicarbonate (70 mL) were added. The layers were separated and the aqueous layer was extracted with diethyl ether (3×20 mL). The combined organic layers were washed with saturated sodium carbonate (50 mL), dried (Na2SO4) and the solvents were removed in vacuo. The resulting solid was purified by column chromatography on silica gel (300 g), eluting with 30% ethyl acetate in hexane to yield 1.0 g (42%) of the title compound as a pale yellow crystalline solid. 1H-NMR (400 MHz, CDCl3): δ 9.89 (br s, 1H), 9.67 (s, 1H), 6.95 (d, 1H, J=4.1 Hz), 6.94 (d, 1H, J=4.1 Hz), 4.38 (q, 2H, J=7.1 Hz), 1.39 (t, 3H, J=7.1). The mixture was heated to reflux for 15 min cooled to RT were added The layers were separated the aqueous layer was extracted with diethyl ether (3×20 mL) The combined organic layers were washed with saturated sodium carbonate (50 mL) dried (Na2SO4) the solvents were removed in vacuo The resulting solid was purified by column chromatography on silica gel (300 g) eluting with 30% ethyl acetate in hexane

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

Procedure: To a mixture of 406A (167 mg, 1.0 mmol), KCN (325.6 mg, 5.0 mmol) in anhydrous EtOH (20 ml) was added AcOH (85.9 μl, 1.5 mmol) followed by activated MnO2 (1.643 g, 20 mmol). The reaction was stirred overnight. After workup, the residue was purified by silica gel flash column chromatography to give 406B (162 mg, 77%) as a pinkish solid (25% EtOAc—hexanes). After workup, the residue was purified by silica gel flash column chromatography

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

Procedure: To a solution of dimethylformamide (21 mL, 0.27 mol) in 75 mL of dichloroethane was added a solution of phosphorus oxychloride (25 mL, 0.27 mol) in 75 mL of dichloroethane at 0° C. The mixture was stirred at room temperature for 30 minutes and cooled to 0° C. To the mixture was added a solution of ethyl pyrrole-2-carboxylate (25 g, 0.18 mol) in 50 mL of dichloroethane dropwise. The resulting mixture was stirred at room temperature for 30 minutes and then at 40° C. for 1 hour. The mixture was poured into ice and basified to pH 11 with 5 N sodium hydroxide solution. The mixture was extracted with ethyl acetate and the extract washed with water, brine and dried over anhydrous sodium sulfate. The two products were separated by column chromatography (1:3 ethyl acetate:hexane) to give 15 g (50% yield) of 5-formyl-1H-pyrrole-2-carboxylic acid ethyl ester and 2 g (7% yield) of 4-formyl-1H-pyrrole-2-carboxylic acid ethyl ester. 1H-NMR (5-formyl-1H-pyrrole-2-carboxylic acid ethyl ester) (300 MHz, dimethylsulfoxide) δ 13.02 (br s, 1H, NH), 9.69 (s, 1H, CHO), 6.95 (d, 1H), 6.86 (d, 1H), 4.27 (q, 2H, CH3), 1.28 (t, 3H, CH3). MS m/z 167 [M+]. cooled to 0° C The resulting mixture was stirred at room temperature for 30 minutes at 40° C. for 1 hour The mixture was extracted with ethyl acetate the extract washed with water, brine dried over anhydrous sodium sulfate The two products were separated by column chromatography (1:3 ethyl acetate:hexane)

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

Procedure: To a solution of dimethylformamide (21 mL, 0.27 mol) in 75 mL of dichloroethane was added a solution of phosphorus oxychloride (25 mL, 0.27 mol) in 75 mL of dichloroethane at 0° C. The mixture was stirred at room temperature for 30 minutes and cooled to 0–20 C. To the mixture was added a solution of ethyl pyrrole-2-carboxylate (25 g, 0.18 mol) in 50 mL of dichloroethane dropwise. The resulting mixture was stirred at room temperature for 30 minutes and then at 40° C. for 1 hour. The mixture was poured into ice and basified to pH 11 with 5 N sodium hydroxide solution. The mixture was extracted with ethyl acetate and the extract washed with water and brine and dried over anhydrous sodium sulfate. The two products were separated by column chromatography (1:3 ethyl acetate:hexane) to give 15 g (50% yield) of 5-formyl-1H-pyrrole-2-carboxylic acid ethyl ester and 2 g (7% yield) of 4-formyl-1H-pyrrole-2-carboxylic acid ethyl ester. 1H-NMR (300 MHz, dimethylsulfoxide) δ 13.02 (br s, 1H, NH), 9.69 (s, 1H, CHO), 6.95 (d, 1H), 6.86 (d, 1H), 4.27 (q, 2H, CH3), 1.28 (t, 3H, CH3). MS m/z 167 [M+]. cooled to 0–20 C The resulting mixture was stirred at room temperature for 30 minutes at 40° C. for 1 hour The mixture was extracted with ethyl acetate the extract washed with water and brine dried over anhydrous sodium sulfate The two products were separated by column chromatography (1:3 ethyl acetate:hexane)