Diethyl Ether → 3-Methoxy-8-(2,4,6-trimethyl-phenyl)-tetrahydro-pyrazolo[1,2-a][1,2,5]triazepine-7,9-dione

Participants

Reaction Conditions

Reaction Steps

To a degassed suspension of 5-methoxy-[1,2,5]triazepane hydrochloride salt (408 mg, 2.0 mmol) and triethylamine (1.115 ml, 810 mg, 8.0 mmol) in diethyl ether (1.0 ml) at 0-5° C. was added a solution of 2-(chlorocarbonyl)-2-mesitylketene [prepared according to Nakanishi's method: S. Nakanishi, K. Butler, Org. Prep. Proced. Int. 7, 155-158 (1975)] (891 mg, 4.0 mmol) in diethyl ether (1.0 ml) dropwise. The suspension was stirred at 0-5° C. for 30 minutes, and at room temperature overnight. The reaction mixture was poured on water (5 ml), the pH made alkaline (pH 14) by addition of aqueous sodium hydroxide, the aqueous layer extracted with ethyl acetate (3×10 ml) and the combined organic layers discarded. The aqueous alkaline phase was acidified with cooling to pH 5 by addition of a 4N HCl solution and the product thoroughly extracted with ethyl acetate (3×20 ml) and dichloromethane (3×20 ml). The combined organic layers were dried over sodium sulfate and concentrated in vacuo. The residue was purified by chromatography on silica gel (gradient ethyl acetate/cyclohexane 5:1→4 ethyl acetate). Yield: 70 mg of 3-methoxy-8-(2,4,6-trimethyl-phenyl)-tetrahydro-pyrazolo[1,2-a][1,2,5]triazepine-7,9-dione (compound P2.1) as a pale beige solid, mp 227-229° C.

Provenance & Evidence