Phosgene → 2-Tert-butoxycarbonyloxyimino-1-phenylbutane-1,3-dione

Participants

Reaction Steps

A solution of 2-hydroxyimino-1-phenylbutane-1,3-dione (3.82 g.) and pyridine (1.62 ml.) in benzene (30 ml.) was dropwise added to a solution of phosgene (1.98 g.) in benzene (25 ml.) over 40 minutes at 5° to 9° C. After stirring for 1 hour at the same temperature, the mixture was allowed to stand overnight. To the resultant solution containing 2-chlorocarbonyloxyimino-1-phenylbutane-1,3-dione was dropwise added, over 30 minutes at 5° C, a solution of tert-butyl alcohol (2.96 g.) and pyridine (3.16 g.) in benzene (30 ml.). After stirring for 1 hour at the same temperature, the mixture was stirred for 6 hours at room temperature, after which the mixture was allowed to stand overnight. Cooled water (100 ml.) was added to the reaction mixture, and the organic layer was in turn washed with water, a 0.5M citric acid aqueous solution (20 ml.) (4 times) and a 5% sodium carbonate aqueous solution (20 ml.) (4 times) until the aqueous layer became almost colorless, and further washed with a sodium chloride aqueous solution and then dried over magnesium sulfate. After drying, the solution was treated with activated charcoal and the solvent was distilled off to give oil (3.48 g.). The oil was partly crystallized by allowing to stand and to the mixture was added ether to precipitate crystals. The precipitates were collected by filtration and recrystallized from a mixed solvent of carbon tetrachloride and petroleum ether to give 2-tert-butoxycarbonyloxyimino-1-phenylbutane-1,3-dione (350 mg.), mp 90° to 103° C (dec).

Provenance & Evidence