Hydrochloric Acid → 2-Carboxy-3-methyl-8-oxo-7-tritylamino-5-thia-1-aza-bicyclo[4.2.0]oct-2-ene

Participants

Reaction Conditions

Reaction Steps

Triethylamine (55.6 cc) is added to a suspension of 7-amino-2-carboxy-3-methyl-8-oxo-5-thia-1-aza-bicyclo[4.2.0]oct-2-ene (42.8 g) in dry N,N-dimethylformamide (250 cc), and after cooling the mixture to -20° C. a solution of chlorotriphenylmethane (55.8 g) in chloroform (250 cc) is added in the course of 2 hours. The reaction mixture is stirred for 24 hours at 25° C. and then poured into normal hydrochloric acid (400 cc). After filtration, the organic phase is separated off, concentrated to half its volume under reduced pressure (40 mm Hg) at 40° C., and taken up in ethyl acetate (400 cc). The aqueous phase is extracted with ethyl acetate (400 cc), and the combined organic phases are washed with normal hydrochloric acid (2×250 cc) and then extracted with a half-saturated sodium bicarbonate solution (4×500 cc). These combined aqueous phases are washed with ethyl acetate (300 cc), then acidified to pH 3 with 12 N hydrochloric acid and extracted with ethyl acetate (2×500 cc). The combined organic solutions are washed with a saturated sodium chloride solution (250 cc), dried over sodium sulphate and concentrated to dryness under reduced pressure (40 mm Hg) at 40° C. The residue is caused to solidify by adding isopropyl ether (250 cc). The solid is filtered off, washed with isopropyl ether (100 cc) and dried. A mixture (22.2 g) of 2-carboxy-3-methyl-8-oxo-7-tritylamino-5-thia-1-aza-bicyclo[4.2.0]oct-2-ene (40%) and its oct-3-ene isomer (60%) is obtained in the form of a cream-coloured solid.

Provenance & Evidence