ethyl 7-chloro-1H-pyrrolo[2,3-c]pyridine-2-carboxylate

To a heterogeneous solution of potassium ethoxide (6.56 g, 77.9 mmol) in diethyl ether (55 mL), was slowly added diethyl oxalate (10.6 mL, 77.9 mmol). A slight exotherm resulted. After stirring 5 min, a homogeneous yellow solution resulted, but after 10 min, a heterogeneous yellow slurry was observed. Addition of 2-chloro-4-methyl-3-nitropyridine (13.45 g, 77.9 mmol) as a solid, with a diethyl ether rinse (23 mL), resulted in a dark violet solution with a dark precipitate. The mixture was stirred at room temperature overnight (21 h). The solid precipitate was filtered, rinsed thoroughly with diethyl ether, and air-dried to give potassium (lZ)-1-(2-chloro-3- nitropyri din-4-yl)-3-ethoxy-3-oxoprop-1-en-2-olate (19.8 g, 63.6 mmol, yield 81percent) as an orange solid. The crude product was used directly without further purification or identification.Potassium (lZ)-l-(2-chloro-3-nitropyridin-4-yl)-3-ethoxy- 3-oxoprop-1-en-2-olate (19.8 g, 63.6 mmol) was dissolved in acetic acid (908 mL) and the solution was treated with iron powder (14.6 g, 280.9 mmol). The reaction mixture was warmed to 60°C and stirred overnight (18.5 h). TLC analysis indicated consumption of the starting material, therefore the reaction mixture was filtered through diatomaceous earth to remove the catalyst. The filtrate was concentrated to dryness. The residue was treated with methylene chloride (ca. 400 mL) and filtered through a plug of silica. Eluting with methylene chloride removed insolubles, and further elution with methylene chloride/ethyl acetate (50: 50) provided ethyl 7- chloro-1H-pyrrolo[2, 3-c]pyridine-2-carboxylate (10.3 g, 45.8 mmol, yield 72percent) as a yellow solid after concentration: Rf 0.80 (silica gel, 50:50 hexanes/ethyl acetate) ; mp 152-157°C; (at)H NMR (300 MHz, CD30D) 81.43 (3H, t, J = 7.0 Hz), 4.44 (2H, q, J = 7.1 Hz), 7.27 (lH, s), 7.65 (1H, d, J = 5.7 Hz), 7.95 (1H, d, J = 5.4 Hz); ESI MS m/z 224 [C10H9ClN2O2 + H] +; HPLC (Method A) >99percent (AUC) , tR = 16. 6 min.Ethyl 7-chloro-1H-pyrrolo[2, 3-c]pyridine-2-carboxylate (0.64 g, 2.85 mmol) was dissolved in tetrahydrofuran (5.7 mL) and methanol (6.8 mL). To the mixture was added 3 N KOH (2.85 mL). After stirring overnight (15.5 h) at room temperature, the reaction mixture was concentrated to dryness. The residue was dissolved in water. This aqueous solution was made acidic (pH 3 using 6 N HCl. The precipitate was collected by filtration. The precipitate was dissolved in methanol and concentrated to dryness to afford 7-chloro-lH-pyrrolo[2, 3- c] pyridine-2-carboxylic acid (0.53 g, 2.7 mmol, 94percent) as a yellow powder: mp 210-214°C; To a heterogeneous solution of potassium ethoxide (6.56 g, 77.9 mmol) in diethyl ether (55 mL), was slowly added diethyl oxalate (10.6 mL, 77.9 mmol). A slight exotherm resulted. After stirring 5 min, a homogeneous yellow solution resulted, but after 10 min, a heterogeneous yellow slurry was observed. Addition of 2-chloro-4-methyl-3-nitropyridine (13.45 g, 77.9 mmol) as a solid, with a diethyl ether rinse (23 mL), resulted in a dark violet solution with a dark precipitate. The mixture was stirred at room temperature overnight (21 h). The solid precipitate was filtered, rinsed thoroughly with diethyl ether, and air-dried to give potassium (lZ)-1-(2-chloro-3- nitropyri din-4-yl)-3-ethoxy-3-oxoprop-1-en-2-olate (19.8 g, 63.6 mmol, yield 81percent) as an orange solid. The crude product was used directly without further purification or identification.Potassium (lZ)-l-(2-chloro-3-nitropyridin-4-yl)-3-ethoxy- 3-oxoprop-1-en-2-olate (19.8 g, 63.6 mmol) was dissolved in acetic acid (908 mL) and the solution was treated with iron powder (14.6 g, 280.9 mmol). The reaction mixture was warmed to 60°C and stirred overnight (18.5 h). TLC analysis indicated consumption of the starting material, therefore the reaction mixture was filtered through diatomaceous earth to remove the catalyst. The filtrate was concentrated to dryness. The residue was treated with methylene chloride (ca. 400 mL) and filtered through a plug of silica. Eluting with methylene chloride removed insolubles, and further elution with methylene chloride/ethyl acetate (50: 50) provided ethyl 7- chloro-1H-pyrrolo[2, 3-c]pyridine-2-carboxylate (10.3 g, 45.8 mmol, yield 72percent) as a yellow solid after concentration: Rf 0.80 (silica gel, 50:50 hexanes/ethyl acetate) ; mp 152-157°C; (at)H NMR (300 MHz, CD30D) 81.43 (3H, t, J = 7.0 Hz), 4.44 (2H, q, J = 7.1 Hz), 7.27 (lH, s), 7.65 (1H, d, J = 5.7 Hz), 7.95 (1H, d, J = 5.4 Hz); ESI MS m/z 224 [C10H9ClN2O2 + H] +; HPLC (Method A) >99percent (AUC) , tR = 16. 6 min.Ethyl 7-chloro-1H-pyrrolo[2, 3-c]pyridine-2-carboxylate (0.64 g, 2.85 mmol) was dissolved in tetrahydrofuran (5.7 mL) and methanol (6.8 mL). To the mixture was added 3 N KOH (2.85 mL). After stirring overnight (15.5 h) at room temperature, the reaction mixture was concentrated to dryness. The residue was dissolved in water. This aqueous solution was made acidic (pH 3 using 6 N HCl. The precipitate was collected by filtration. The precipitate was dissolved in methanol and concentrated to dryness to afford 7-chloro-lH-pyrrolo[2, 3- c] pyridine-2-carboxylic acid (0.53 g, 2.7 mmol, 94percent) as a yellow powder: mp 210-214°C;

Molecular Weight:224.64
XLogP3:2.5
Hydrogen Bond Donor Count:1
Hydrogen Bond Acceptor Count:3
Rotatable Bond Count:3
Exact Mass:224.0352552
Monoisotopic Mass:224.0352552
Topological Polar Surface Area:55
Heavy Atom Count:15
Complexity:250
Covalently-Bonded Unit Count:1
Compound Is Canonicalized:Yes