Acetic Anhydride → HCID 20461628, compound

Participants

Reaction Steps

A mixture of one cis and two trans-isomers of 4-allyl-3-(1-hydroxyethyl)-1-(1-benzyloxycarbonyl-1-triphenylphosphoranylidenemethyl)azetidin-2-one (5.0 g) in dry dichloromethane (150 cm3) was treated with 4-N,N-dimethylaminopyridine (1.22 g) followed by acetic anhydride (2.27 g) and the solution was stirred overnight at room temperature. The solution was evaporated under reduced pressure and the residue was chromatographed using high performance liquid chromatography, eluting with a 6:4 ethyl acetate/60°-80° petroleum ether mixture. This gave one cis and two trans-isomers of 4-allyl-3-(1-acetoxyethyl)-1-(1-benzyloxycarbonyl-1-triphenylphosphoranylidenemethyl)azetidin-2-one. The yields were the cis isomer (1.10 g, 21%) one trans isomer (0.28 g, 5%) and the other trans isomer (1.23 g, 23%). The cis-isomer crystallised (m.p. 156°-160° decomp). The infra-red spectra of all three isomers were identical; νmax (CHCl3) 3000, 1730, 1635 and 1610 cm-1.

Provenance & Evidence