Diisopropylethylamine → ethyl 4-((1R,3S)-3-amino-2,2,3-trimethylcyclopentylamino)-3-carbamoylpyrrolo[1,2-b]pyridazine-6-carboxylate

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Reaction Conditions

Reaction Steps

N,N-Diisopropylethylamine (7.18 mL, 41.1 mmol) was added to a mixture of ethyl 3-carbamoyl-4-chloropyrrolo[1,2-b]pyridazine-6-carboxylate (3.67 g, 13.71 mmol, from Preparation 4), (1S,3R)-1,2,2-trimethylcyclopentane-1,3-diamine (2.93 g, 20.57 mmol, prepared according to conditions described in Tetrahedron Asymmetry 2001, 12, 1579 and Eur. J. Inorg. Chem. 2006, 839) and N,N-dimethylformamide (50 mL). The mixture was stirred in a 90° C. oil bath for 1 h, quenched with saturated sodium bicarbonate (250 mL) and extracted with ethyl acetate (4×200 mL). The combined extracts were dried (MgSO4), filtered, concentrated and pumped under vacuum. The solid residue was treated with ethyl acetate (60 mL) and sonicated for 10 min. Vacuum filtration gave the first batch of the title compound (2.292 g). The filtrate was concentrated to dryness. The solid residue was treated with dichloromethane (5 mL), ethyl acetate (4 mL) and hexanes (16 mL). The mixture was sonicated for 15 min and filtered. The solid was washed with 20% ethyl acetate in hexanes to give second batch of the title compound (2.146 g). The combined amount of the title compound was 4.438 g (87% yield). 1H NMR (500 MHz, methanol-d4) δ ppm 8.19 (1 H, s), 8.00 (1 H, d, J=1.66 Hz), 7.33 (1 H, d, J=1.66 Hz), 4.47 (1 H, t, J=8.18 Hz), 4.35 (2 H, q, J=7.03 Hz), 2.21-2.49 (1 H, m), 1.77-1.93 (2 H, m), 1.63-1.75 (1 H, m), 1.38 (3 H, t, J=7.21 Hz), 1.21 (3 H, s), 1.07 (3 H, s), 0.96 (3 H, s); MS (ES+) m/z: 374.2 (M+H); HPLC retention time: 2.975 min (analytical HPLC Method F).

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