Diethyl 2-[(2S)-1-(tert-butoxycarbonyl)pyrrolidinyl]-4-[6-(ethoxycarbonyl)-3-pyridazinyl]-6-(4-fluorobenzyl)-3,5-pyridinedicarboxylate → Ethyl 4-[6-(ethoxycarbonyl)-3-pyridazinyl]-2-(4-fluorobenzyl)-5-oxo-7,8,9,9a-tetrahydro-5H-pyrido[2,3-a]pyrrolizine-3-carboxylate

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Reaction Steps

Diethyl 2-[(2S)-1-(tert-butoxycarbonyl)pyrrolidinyl]-4-[6-(ethoxycarbonyl)-3-pyridazinyl]-6-(4-fluorobenzyl)-3,5-pyridinedicarboxylate (E, 260 mg crude) was first dissolved in 15 ml mixture of trifluoroacetic acid and dichloromethane (2 to 1 ratio) and stirred for 1 hour followed by the removal of the solvent. To this residue, 15 ml of mixture of triethylamine and dichloromethane (1 to 2 ratio) was added and the mixture was stirred for 2 hours. Upon removal of the solvent, the residue was purified by flash chromatography. 145 mg solid was obtained. 1H NMR (400 MHz, CDCl3) δ 8.21 (d, 1H), 8.03 (d, 1H), 7.18 (t, 2H), 6.90 (t, 2H), 4.75 (m, 1H), 4.54 (q, 2H), 4.42 (m, 2H), 3.96 (q, 2H), 3.65 (m, 1H), 3.38 (m, 1H), 2.45 (m, 1H), 2.32 (m, 2H), 1.45 (t, 3H), 1.40 (m, 1H), 0.92 (t, 3H) ppm. ESI-MS m/z 505 (M+H)+.

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