Reaction Steps
A solution of 2,4,5-trichlorophenylthioacetic acid (6.0 g, 22.1 mmol) in methylene chloride (30 mL) and thionyl chloride (10 mL, 137 mmol) was heated at reflux for 3 h. The reaction mixture was allowed to cool to room temperature and was concentrated in vacuo. The residue was evaporated two times from toluene (50 mL) to give 6.7 g of 2,4,5-trichlorophenylthioacetyl chloride as a pale yellow oil (100% yield). 1H NMR (300 MHz, CDCl3) a 4.12 (s, 2 H), 7.54 (s, 1 H), 7.56 (s, 1 H). A solution of (6R)-trans-3-chloromethyl-7-amino-8-oxo-5-thia-1-azabicyclo-[4.2.0]oct-2-ene-2-carboxylate, diphenylmethyl ester (4.15 g, 10 mmol) in THF (50 mL) was cooled to 0° C. and treated with N-methylmorpholine (1.2 g, 11.9 mmol) and 2,4,5-trichlorophenylthioacetyl chloride (3.3 g, 10.8 mmol). The reaction mixture was stirred for 1 h at 0° C., diluted with ethyl acetate (500 mL) and washed with water (500 mL). The organic solution was then dried (MgSO4) and the solvents were evaporated in vacuo. The remaining residue was stirred with ether. The product solidified and was collected by filtration to give 4.5 g (60% yield) of title product as a white solid, m.p. 173° C. 1H NMR (300 MHz, CDCl3)δ 3.45 (d, J=18.3 Hz, 1 H), 3.61 (d, J=18.3 Hz, 1 H), 3.68 (d, J=16.8 Hz, 1 H), 3.76 (d, J=16.8 Hz, 1 H), 4.37 (d, J=11.9 Hz, 1 H), 4.42 (d, J=11.9 Hz, 1 H), 4.98 (d, J=5.0 Hz, 1 H), 5.80 (dd, J=5.0, 8.9 Hz, 1 H), 6.99 (s, 1 H), 7.22 (d, J=8.9 Hz, 1 H), 7.30-7.45 (m, 10 H), 7.38 (s, 1 H), 7.51 (s, 1 H). Anal. Calcd. for C29H22N2O4S2Cl4 : C, 52.11; H, 3.32; N, 4.19. Found: C, 52.06; H, 3.42; N, 4.19.
