Potassium Carbonate → 2-t-Butoxycarbonylamino-4-ethynyl-thiophene-3-carboxylic acid ethyl ester

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Reaction Steps

2-t-Butoxycarbonylamino-4-formyl-thiophene-3-carboxylic acid ethyl ester (6.35 g, 21.31 mmol) from example 240d was dissolved in absolute EtOH (325 mL). This was treated with potassium carbonate (%.89 g, 42.62 mmol) followed by (1-diazo-2-oxopropyl)-phosphonic acid dimethyl ester (4.91 g, 25.57 mmol). The reaction was stirred at room temperature for 14 hr. The reaction was concentrated to 12 volume then poured into sat. NaHCO3 (250 mL) and then extracted with EtOAc (3×250 mL). The combined extracts were washed with brine (2×250 mL). They were dried (Na2SO4), filtered and the solvent removed in vacuo. The crude product was purified by flash chromatography (SiO2, 1 EtOAc/9 hexanes) to afford the title compound (5.86 g, 93%). MS m/e (CI) 296.0 (M+H), 313.1 (M+NH4); 1H NMR (300 MHz, CDCl3): δ ppm 1.41 (t, 3H), 1.53 (s, 9H), 3.11 (s, 1H), 4.37 (q, 2H), 6.98 (s, 1H), 10.30 (s, 1H).

Provenance & Evidence