6,6-dimethylpiperidine-2,4-dione

Conditions: temp:0.00; pressure:0.00; stir:

Conditions: temp:0.00; pressure:0.00; stir:

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

Procedure: A mixture of methyl 6,6-dimethylpiperidine-2,4-dione-3-carboxylate (26.3 g), water (30 ml) and concentrated hydrochloric acid (3 drops) in acetonitrile (300 ml) was heated at reflux for 4 hours. The cooled solution was evaporated under reduced pressure and the residue recrystallised from water (50 ml) to give 6,6-dimethylpiperidine-2,4-dione (7.3 g), mp 183°-184° C., as a cream crystalline solid. was heated at reflux for 4 hours The cooled solution was evaporated under reduced pressure the residue recrystallised from water (50 ml)

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

Procedure: A solution of 4-chloro-2-nitrobenzoyl chloride (4.4 g) in dry dichloromethane (5 ml) was added at 5°-10° C. to a stirred solution of 6,6-dimethylpiperidine-2,4-dione (2.8 g) and triethylamine (2.8 ml) in dry dichloromethane (50 ml) and the mixture was stirred at ambient temperature for 18 hours. Triethylamine (8.4 ml) and acetone cyanohydrin (0.4 ml) were added successively to the solution and the mixture was stirred at ambient temperature for 4 hours. The resulting solution was washed successively with 2N hydrochloric acid (25 ml) and water (3×25 ml), dried over sodium sulphate and evaporated under reduced pressure to give a yellow solid which was recrystallised from acetonitrile to give 3-(4-chloro-2-nitrobenzoyl)-6,6-dimethylpiperidine-2,4-dione (4 g), mp 162°-162.5° C., as a yellow crystalline solid. the mixture was stirred at ambient temperature for 4 hours The resulting solution was washed successively with 2N hydrochloric acid (25 ml) and water (3×25 ml) dried over sodium sulphate evaporated under reduced pressure to give a yellow solid which was recrystallised from acetonitrile

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

Procedure: Ethyl 6,6-dimethyl-2,4-dioxopiperidine-3-carboxylate (0.69 g, 3.23 mmol) was dissolved in acetonitrile containing 1% of water (15 mL) and the resulting solution was refluxed for 2 hours. After evaporating to dryness, the crude material was suspended in isopropyl ether, kept under vigorous stirring and filtered to give the title compound (387 mg, Y=85%) as a light brown solid. the resulting solution was refluxed for 2 hours After evaporating to dryness filtered