Methanol → p-Toluenesulfonic acid

Participants

Reaction Conditions

Reaction Steps

To a solution of benzyl 7-phenoxyacetamido-8-oxo-3-trifluoromethanesulfonyl-5-thia-1,3-diazabicyclo-[4,2,0]octane-2-carboxylate (1.50 g.) and N,N-dimethylaniline (0.41 ml.) in methylene chloride (30 ml.) was added phosphorus pentachloride (1.115 g.) at -35° C. under nitrogen atmosphere, and the mixture was stirred at -30° to -25° C. for 2.3 hours. The reaction mixture was cooled to -55° C., and thereto was added methanol (2.4 ml.). This mixture was allowed to warm to 0° C. over a period of 2 hours. Thereto was added water (2.4 ml.), and after stirring at 0° C. for an hour, the reaction mixture was poured into ice-water and extracted twice with ethyl acetate (120 ml. and 50 ml.). The combined extracts were washed with a small amount of water, a dilute aqueous solution of potassium dihydrogenphosphate, a phosphate buffer solution (pH 7,×2) and an aqueous solution of sodium chloride, successively. After drying over magnesium sulfate and filtration, to the filtrate was added p-toluene-sulfonic acid monohydrate (509 mg.) and concentrated to give a crystalline residue, to which diethyl ether was added. The crystals were collected by filtration and washed with diethyl ether to afford p-toluene-sulfonicacid salt of benzyl 7-amino-8-oxo-3-trifluoromethanesulfonyl-5-thia-1,3-diazabicyclo[4,2,0]octane-2-carboxylate (1.365 g.), mp 155°-158° C. (dec.).

Provenance & Evidence