1-(Triphenylphosphoranylidene)acetone → methylene-(2S,5R)-6-[(E)-acetonylidene]-3,3-dimethyl-7-oxo-4-thia-1-azabicyclo[3.2.0]heptane-2-carboxylate pivalate

Participants

Reaction Steps

A solution of 3.5 g of methylene-6,7-dioxo-3,3-dimethyl-4-thia-1-azabicyclo[3.2.0]heptane-2-carboxylate pivalate in 150 ml of benzene is treated at room temperature with 6.3 g of 1-triphenylphosphoranylidene-2-propanone. After 10 minutes, the reaction mixture is evaporated. The residue is chromatographed on silica gel while eluting with cyclohexane/ethyl acetate (6:4). There are obtained methylene-(2S,5R)-6-[(E)-acetonylidene]-3,3-dimethyl-7-oxo-4-thia-1-azabicyclo[3.2.0]heptane-2-carboxylate pivalate [Rf: 0.47; cyclohexane/ethyl acetate (6:4); NMR (CDCl3), δ (ppm): 1.24 (9H); 1.52 (3H); 1.62 (3H); 2.62 (3H, Ac); 4.65 (1H3); 5.82 (1H5); 5.9 (m, 2H); 6.11 (1H)] and methylene-(2S,5R)-6-[(Z)-acetonylidene]-3,3-dimethyl-7-oxo-4-thia-1-azabicyclo[3.2.0]heptane-2-carboxylate pivalate [Rf: 0.53; cyclohexane/ethyl acetate (6:4); NMR (CDCl3), δ (ppm): 1.25 (9H); 1.53 (3H); 1.61 (3H); 2.38 (3H, Ac); 4.64 (1H3); 5.91 (m, 2H); 6.08 (1H5): 6.63 (1H)].

Provenance & Evidence