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

Participants

Reaction Steps

LCMS (Method A): m/z 406 (M+H)+ (ES+), at 1.81 min, UV inactive tert-Butyl 2-{4-[(1-methylcyclobutyl)carbamoyl]piperidin-1-yl}-6-azaspiro[3.4]octane-6-carboxylate (0.627 g, 1.55 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 (0.49 g, 0.65 mL, 4.64 mmol) and ethyl chloroformate (0.25 mg, 0.18 mL, 0.57 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 and sat. NaHCO3 sol., organic layer washed with sat. NaCl sol. and dried over MgSO4. The residue was purified by column chromatography (normal phase, [Biotage SNAP cartridge KP-sil 10 g, 40-63 μm, 60 A, 12 mL per min, gradient 0% to 10% MeOH in DCM]) to give ethyl 2-{4-[(1-methylcyclobutyl)carbamoyl]piperidin-1-yl}-6-azaspiro[3.4]octane-6-carboxylate (0.04 g, 13%) as a yellow gum as a mixture of diastereomers.

Provenance & Evidence