Trifluoroacetic acid → 1-(6-azaspiro[3.4]oct-2-yl)-N-(1-methylcyclobutyl)piperidine-4-carboxamide trifluoroacetate

Participants

Reaction Steps

tert-Butyl 2-{4-[(1-methylcyclobutyl)carbamoyl]piperidin-1-yl}-6-azaspiro[3.4]octane-6-carboxylate (0.747 g, 1.84 mmol) was dissolved in DCM (8 mL) and TFA (2 mL) was added. The reaction mixture was stirred at rt overnight under nitrogen, then the solvents were removed in vacuo, to give 1-(6-azaspiro[3.4]oct-2-yl)-N-(1-methylcyclobutyl)piperidine-4-carboxamide trifluoroacetate as a dark yellow oil which was used directly without further purification. The residue was dissolved in DCM (10 mL) and NEt3 (0.56 g, 0.77 mL, 5.52 mmol) and 4-nitrophenyl chloroformate (0.555 g, 2.76 mmol) were added and the reaction mixture was stirred at rt overnight under nitrogen. The solvents were removed in vacuo, and the residue was partitioned between DCM (15 mL) and 1 N NaOH sol. (15 mL). The aqueous layer was extracted with DCM (4×20 mL), dried over MgSO4 and the solvent evaporated. The residue was semi-purified by column chromatography (normal phase, [Biotage SNAP cartridge KP-sil 25 g, 40-63 μm, 60 A, 25 mL per min, gradient 0% to 10% MeOH in DCM]) to give 4-nitrophenyl 2-{4-[(1-methylcyclobutyl)carbamoyl]piperidin-1-yl}-6-azaspiro[3.4]octane-6-carboxylate (0.60 g, 69%) as a yellow gum as a mixture of diastereomers.

Provenance & Evidence