Water → Ethyl 4-[4-methyl-4-(ethoxycarbonyl)piperidin-1-yl]azepane-1-carboxylate

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Reaction Steps

Ethyl-4-methylpiperidine-4-carboxylate hydrochloride (0.50 g, 2.42 mmol) was dissolved in methanol (10 mL) and treated with K2CO3 (0.33 g, 2.42 mmol) in a minimum of water to de-salt. Reaction mixture was concentrated in vacuo and azeotroped to dryness with toluene. The residue and 4-oxoazepane-1-carboxylic acid ethyl ester (0.45 g, 2.42 mmol) were dissolved in DCM (20 mL) at rt and titanium isopropoxide (0.76 g, 0.8 mL, 2.66 mmol) was added. The reaction mixture was stirred at rt for 5 h. STAB (2.05 g, 9.66 mmol) and acetic acid (0.3 mL) were added and the reaction mixture was stirred at rt overnight under nitrogen. The reaction mixture was quenched with the addition of water (5 mL) and stirred for 5 minutes. The reaction mixture was diluted with DCM and filtered through a pad of celite. The filtrate was washed with sat. NaHCO3 sol., sat. NaCl sol. and dried over MgSO4. The solvents were removed in vacuo, and the residue was purified by column chromatography (normal phase, [Biotage SNAP cartridge KP-sil 25 g, 40-63 μm, 60 Å, 25 mL per min, gradient 0% to 4% MeOH in DCM]) to give ethyl 4-[4-methyl-4-(ethoxycarbonyl)piperidin-1-yl]azepane-1-carboxylate (0.37 g, 45.0%) as a pale yellow oil.

Provenance & Evidence