Sulfuric Acid → Ethyl 3-carbamoyl-4-chloropyrrolo[1,2-b]pyridazine-6-carboxylate

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Reaction Steps

To a round bottom flask was added concentrated H2SO4 (100 mL) followed by ethyl 4-chloro-3-cyanopyrrolo[1,2-b]pyridazine-6-carboxylate (10 g, 40 mmol). The reaction was stirred at room temperature under nitrogen overnight. The reaction mixture was poured onto ice cold saturated sodium carbonate solution. The aqueous solution was extracted with EtOAc (4×) and the combined organic layer was concentrated to yield 7 g (70%) of the title compound as a yellow solid. HPLC (condition S): retention time=8.04 min. LCMS (condition A): m/z=268.0 +ve. 1H NMR (400 MHz, CDCl3) δ ppm: 8.49 (1H, d, J=1.6 Hz), 8.40 (1H, s), 8.08 & 7.98 (1H, two br s), 7.12 (1H, d, J=1.6 Hz), 4.34 (2H, q, J=7.2 Hz), 1.34 (3H, t, J=7.2 Hz).

Provenance & Evidence