Water → 2-(3-Chloro-propyl)-3-oxo-2,3-dihydro-indazole-1-carboxylic acid ethyl ester

Participants

Reaction Steps

To a solution of 3-oxo-2,3-dihydro-indazole-1-carboxylic acid ethyl ester (410 mg, 2 mmol) dissolved in dry DMF (10 ml) is added sodium hydride (60% w/w in oil, 120 mg, 3 mmol). The resulting cloudy solution is allowed to stir for 1 h at rt and is added dropwise under inert atmosphere via a syringe onto a solution of iodochloropropane (268 μl, 2.5 mmol) in dry DMF (2 ml). The resulting solution is allowed to stir at rt overnight. By addition of water and evaporation under reduced pressure most of the DMF is removed from the crude mixture. The residue is dissolved in AcOEt (25 ml) and the resulting organic phase is washed 3 times with water and once with brine. The crude product is purified by chromatography on silica gel (AcOEt/heptane, 2:3), yielding the title compound (78 mg) in 15% as a colourless oil: tR=2.17 min (LC-2), ESI-MS (pos.): m/z 283.05 [M+H]+; 1H-NMR (CDCl3): δ (ppm) 1.38 (t, 3H, CH3), 2.08 (quint., 2H, CH2CH2N), 3.42 (t, 2H, CH2Cl), 4.25 (t, 2H, NCH2), 4.39 (q, 2H, OCH2CH3), 7.22 (t, 1Harom), 7.53 (t, 1Harom), 7.79 (t, 2Harom), and 3-(3-chloro-propoxy)-indazole-1-carboxylic acid ethyl ester (125 mg) in 24% as a colourless oil: tR=2.49 min (LC-2), ESI-MS (pos.): m/z 283.05 [M+H]+; 1H-NMR (CDCl3): δ (ppm) 1.44 (t, 3H, CH3), 2.26 (quint., 2H, CH2CH2N), 3.71 (t, 2H, CH2Cl), 4.49 (q, 2H, OCH2CH3), 4.59 (t, 2H, OCH2CH2), 7.20 (t, 1H, m), 7.46 (t, 1Harom), 7.59 (d, 1 Harom), 8.02 (d, 1Harom). 3-(3-Chloro-propoxy)-indazole-1-carboxylic acid ethyl ester is used as alkylating agent D-06d in the preparation of Precursor D-06b.

Provenance & Evidence