methyl 2-oxopiperidine-4-carboxylate

Conditions: temp:0.00; pressure:0.00; stir:; See reaction.notes.procedure_details.

Procedure: Add benzamidoxime (5.63 g, 41.36 mmol) to a 1M solution of potassium t-butoxide (31 mL, 31 mmol) in tetrahydrofuran and anhydrous tetrahydrofuran (442 mL). Add methyl 2-oxopiperidine-4-carboxylate (5 g, 31.8 mmol) and stir overnight at room temperature. Pour reaction over saturated aqueous sodium bicarbonate and extract into chloroform. Separate layers and extract the aqueous phase with additional chloroform. Dry the combined organic layers over anhydrous magnesium sulfate, filter, and concentrate to dryness under reduced pressure. Purify the resulting residue by flash chromatography (silica gel), eluting with 1-5% 7 N ammoniated methanol in dichloromethane to afford the title compound (4.15 g). 1H NMR (CDCl3) δ 2.19 (m, 1H), 2.34 (m, 1H), 2.8-2.95 (m, 2H), 3.44-3.52 (m, 2H), 3.57 (m, 1H), 6.13 (bs, 1H), 7.45-7.54 (m, 3H), 8.0-8.11 (m, 2H). Pour extract into chloroform Separate layers and extract the aqueous phase with additional chloroform Dry the combined organic layers over anhydrous magnesium sulfate filter concentrate to dryness under reduced pressure Purify the resulting residue by flash chromatography (silica gel) eluting with 1-5% 7 N ammoniated methanol in dichloromethane

Conditions: temp:0.00; pressure:0.00; stir:; See reaction.notes.procedure_details.

Procedure: Add Lawesson's reagent (9.2 g, 22.7 mmol) to a solution of methyl 2-oxopiperidine-4-carboxylate (6.5 g, 41.4 mmol) in toluene (83 mL) and heat to reflux for 2 hours. Cool the solution and concentrate to dryness under reduced pressure. Purify the residue by flash chromatography on silica gel, eluting with ethyl acetate:dichloromethane (gradient 5-15%) to afford the title compound (6.95 g). 1H NMR (CDCl3) δ 1.97 (m, 1H), 2.17 (m, 1H), 2.78 (m, 1H), 3.03 (m, 1H), 3.24 (m, 1H), 3.39 (m, 1H), 3.49 (m, 1H), 3.72 (s, 3H), 8.48 (bs, 1H). heat to reflux for 2 hours Cool the solution concentrate to dryness under reduced pressure Purify the residue by flash chromatography on silica gel eluting with ethyl acetate