ethyl 2,4-dimethyl-1H-pyrrole-3-carboxylate

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:10.01; pressure:0.00; stir:; See reaction.notes.procedure_details.

Procedure: Dimethylformamide (322 g) and dichloromethane (3700 mL) were cooled in an ice bath to 4° C. and phosphorus oxychloride (684 g) was added with stirring. Solid 2,4-dimethyl-1H-pyrrole-3-carboxylic acid ethyl ester (670 g) was slowly added in aliquots over 15 minutes. The maximum temperature reached was 18° C. The mixture was heated to reflux for one hour, cooled to 10° C. in an ice bath and 1.6 L of ice water was rapidly added with vigorous stirring. The temperature increased to 15° C. 10 N Hydrochloric acid (1.6 L) was added with vigorous stirring. The temperature increased to 22° C. The mixture was allowed to stand for 30 minutes and the layers allowed to separate. The temperature reached a maximum of 40° C. The aqueous layer was adjusted to pH 12-13 with 10 N potassium hydroxide (3.8 L) at a rate that allowed the temperature to reach and remain at 55° C. during the addition. After the addition was complete the mixture was cooled to 10° C. and stirred for 1 hour. The solid was collected by vacuum filtration and washed four times with water to give 5-formyl-2,4-dimethyl-1H-pyrrole-3-carboxylic acid ethyl ester (778 g, 100% yield) as a yellow solid. 1H-NMR (DMSO-d6) δ 1.25 (t, 3H, CH3), 2.44, 2.48 (2×s, 2×3H, 2×CH3), 4.16 (q, 2H, CH2), 9.59 (s, 1H, CHO), 12.15 (br s, 1H, NH). MS m/z 195 [M+1]. reached was 18° C The mixture was heated to reflux for one hour The temperature increased to 15° C The temperature increased to 22° C to separate a maximum of 40° C remain at 55° C. during the addition After the addition was cooled to 10° C. stirred for 1 hour The solid was collected by vacuum filtration washed four times with water

Conditions: temp:54.01; pressure:0.00; stir:; See reaction.notes.procedure_details.

Procedure: 3,5-Dimethyl-1H-pyrrole-2,4-dicarboxylic acid 2-tert-butyl ester 4-ethyl ester (2600 g) and ethanol (7800 mL) were stirred vigorously while 10 N hydrochloric acid (3650 mL) was slowly added. The temperature increased from 25° C. to 35° C. and gas evolution began. The mixture was warmed to 54° C. and stirred with further heating for one hour at which time the temperature was 67° C. The mixture was cooled to 5° C. and 32 L of ice and water were slowly added with stirring. The solid was collected by vacuum filtration and washed three times with water. The solid was air dried to constant weight to give of 2,4-dimethyl-1H-pyrrole-3-carboxylic acid ethyl ester (1418 g, 87% yield) as a pinkish solid. 1H-NMR (dimethylsulfoxide-d6) δ2.10, 2.35 (2×s, 2×3H, 2×CH3), 4.13 (q, 2H, CH2), 6.37 (s, 1H, CH), 10.85 (s, 1H, NH). MS m/z 167 [M+1]. was slowly added The temperature increased from 25° C. to 35° C. with further heating for one hour at which time the temperature was 67° C The mixture was cooled to 5° C. with stirring The solid was collected by vacuum filtration washed three times with water dried to constant weight

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

Procedure: Dimethylformamide (322 g) and dichloromethane (3700 mL) were cooled in an ice bath to 4° C. and phosphorus oxychloride (684 g) was added with stirring. Solid 2,4-dimethyl-1H-pyrrole-3-carboxylic acid ethyl ester (670 g) was slowly added in aliquots over 15 minutes. The maximum temperature reached was 18° C. The mixture was heated to reflux for one hour, cooled to 10° C. in an ice bath and 1.6 L of ice water was rapidly added with vigorous stirring. The temperature increased to 15° C. 10 N Hydrochloric acid (1.6 L) was added with vigorous stirring. The temperature increased to 22° C. The mixture was allowed to stand for 30 minutes and the layers allowed to separate. The temperature reached a maximum of 40° C. The aqueous layer was adjusted to pH 12-13 with 10 N potassium hydroxide (3.8 L) at a rate that allowed the temperature to reach and remain at 55° C. during the addition. After the addition was complete the mixture was cooled to 10° C. and stirred for 1 hour. The solid was collected by vacuum filtration and washed four times with water to give 5-formyl-2,4-dimethyl-1H-pyrrole-3-carboxylic acid ethyl ester (778 g, 100% yield) as a yellow solid. 1H-NMR (DMSO-d6) δ1.25 (t, 3H, CH3), 2.44, 2.48 (2×s, 2×3H, 2×CH3), 4.16 (q, 2H, CH2), 9.59 (s, 1H, CHO), 12.15 (br s, 1H, NH). MS m/z 195 [M+1]. reached was 18° C The mixture was heated to reflux for one hour The temperature increased to 15° C The temperature increased to 22° C to separate a maximum of 40° C remain at 55° C. during the addition After the addition was cooled to 10° C. stirred for 1 hour The solid was collected by vacuum filtration washed four times with water

Conditions: temp:54.01; pressure:0.00; stir:; See reaction.notes.procedure_details.

Procedure: 3,5-Dimethyl-1H-pyrrole-2,4-dicarboxylic acid 2-tert-butyl ester 4-ethyl ester (2600 g) and ethanol (7800 mL) were stirred vigorously while 10 N hydrochloric acid (3650 mL) was slowly added. The temperature increased from 25° C. to 35° C. and gas evolution began. The mixture was warmed to 54° C. and stirred with further heating for one hour at which time the temperature was 67° C. The mixture was cooled to 5° C. and 32 L of ice and water were slowly added with stirring. The solid was collected by vacuum filtration and washed three times with water. The solid was air dried to constant weight to give 2,4-dimethyl-1H-pyrrole-3-carboxylic acid ethyl ester (1418 g, 87% yield) as a pinkish solid. 1H-NMR (dimethylsulfoxide-d6) δ2.10, 2.35 (2×s, 2×3H, 2×CH3), 4.13 (q, 2H, CH2), 6.37 (s, 1H, CH), 10.85 (s, 1H, NH). MS m/z 167 [M+1]. was slowly added The temperature increased from 25° C. to 35° C. with further heating for one hour at which time the temperature was 67° C The mixture was cooled to 5° C. with stirring The solid was collected by vacuum filtration washed three times with water dried to constant weight

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:10.01; pressure:0.00; stir:; See reaction.notes.procedure_details.

Procedure: Dimethylformamide (322 g) and dichloromethane (3700 mL) were cooled in an ice bath to 4° C. and phosphorus oxychloride (684 g) was added with stirring. Solid 2,4-dimethyl-1H-pyrrole-3-carboxylic acid ethyl ester (670 g) was slowly added in aliquots over 15 minutes. The maximum temperature reached was 18° C. The mixture was heated to reflux for one hour, cooled to 10° C. in an ice bath and 1.6 L of ice water was rapidly added with vigorous stirring. The temperature increased to 15° C. 10 N Hydrochloric acid (1.6 L) was added with vigorous stirring. The temperature increased to 22° C. The mixture was allowed to stand for 30 minutes and the layers allowed to separate. The temperature reached a maximum of 40° C. The aqueous layer was adjusted to pH 12-13 with 10 N potassium hydroxide (3.8 L) at a rate that allowed the temperature to reach and remain at 55° C. during the addition. After the addition was complete the mixture was cooled to 10° C. and stirred for 1 hour. The solid was collected by vacuum filtration and washed four times with water to give 5-formyl-2,4-dimethyl-1H-pyrrole-3-carboxylic acid ethyl ester (778 g, 100% yield) as a yellow solid. 1H-NMR (DMSO-d6) δ1.25 (t, 3H, CH3), 2.44, 2.48 (2×s, 2×3H, 2×CH3), 4.16 (q, 2H, CH2), 9.59 (s, 1H, CHO), 12.15 (br s, 1H, NH). MS m/z 195 [M+1]. reached was 18° C The mixture was heated to reflux for one hour The temperature increased to 15° C The temperature increased to 22° C to separate a maximum of 40° C remain at 55° C. during the addition After the addition was cooled to 10° C. stirred for 1 hour The solid was collected by vacuum filtration washed four times with water

Conditions: temp:54.01; pressure:0.00; stir:; See reaction.notes.procedure_details.

Procedure: 3,5-Dimethyl-1H-pyrrole-2,4-dicarboxylic acid 2-tert-butyl ester 4-ethyl ester (2600 g) and ethanol (7800 mL) were stirred vigorously while 10 N hydrochloric acid (3650 mL) was slowly added. The temperature increased from 25° C. to 35° C. and gas evolution began. The mixture was warmed to 54° C. and stirred with further heating for one hour at which time the temperature was 67° C. The mixture was cooled to 5° C. and 32 L of ice and water were slowly added with stirring. The solid was collected by vacuum filtration and washed three times with water. The solid was air dried to constant weight to give 2,4-dimethyl-1H-pyrrole-3-carboxylic acid ethyl ester (1418 g, 87% yield) as a pinkish solid. 1H-NMR (dimethylsulfoxide-d6) δ2.10, 2.35 (2×s, 2×3H, 2×CH3), 4.13 (q, 2H, CH2), 6.37 (s, 1H, CH), 10.85 (s, 1H, NH). MS m/z 167 [M+1]. was slowly added The temperature increased from 25° C. to 35° C. with further heating for one hour at which time the temperature was 67° C The mixture was cooled to 5° C. with stirring The solid was collected by vacuum filtration washed three times with water dried to constant weight