反应详情

A solution of 5.5 g (18.8 mmole) of methyl cis-3-amino-1-(2,4-dimethoxybenzyl)-4-oxoazetidine-2-carboxylate in 100 ml of dry toluene was cooled to -78° and 2.5ml (18.8 mmole) of triethylamine was added followed by rapid addition of 35 ml (42mmole) of a 12% solution of phosgene in benzene. The mixture was stirred 15 min at -78°, 3 hours at -45°(acetonitrile-dry ice), then warmed to room temperature and concentrated to half volume in vacuo. To the resulting solution was added 50 ml of t-butanol and the mixture was stirred at room temperature overnight. The solvents were removed in vacuo and the residue diluted with ethyl acetate and filtered. The filtrate was transferred to a separatory funnel and washed with 5% aqueous sodium bicarbonate, 5% hydrochloric acid and brine, dried (MgSO4) and evaporated to dryness. Recrystallization of the crude, crystalline product from ether gave methyl cis-3-t-butoxycarbonylamino-1-(2,4-dimethoxybenzyl)-4-oxoazetidine-2-carboxylate, mp 134°-135°.

1. concentrationconcentrated to half volume in vacuo
2. additionTo the resulting solution was added 50 ml of t-butanol
3. customThe solvents were removed in vacuo
4. additionthe residue diluted with ethyl acetate
5. filtrationfiltered
6. customThe filtrate was transferred to a separatory funnel
7. washwashed with 5% aqueous sodium bicarbonate, 5% hydrochloric acid and brine
8. dry with materialdried (MgSO4)
9. customevaporated to dryness
10. customRecrystallization of the crude, crystalline product from ether