Toluene → Methyl cis-3-t-butoxycarbonylamino-1-(2,4-dimethoxybenzyl)-4-oxoazetidine-2-carboxylate

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Reaction Steps

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 2.5 ml (18.8 mmole) of triethylamine was added followed by rapid addition of 35 ml (42 mmole) 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, m.p. 134°-135°.

Provenance & Evidence