Reductive cross-coupling of 3-substituted delta 3-cephems with alkenyl halides in an Al/PbBr2/NiBr2(bpy) triplemetal redox system. Synthesis of 3-alkenyl-delta 3-cephems.

Synthesis of 3-alkenyl-delta 3-cephems was performed successfully by cross-coupling 3-(trifluoromethylsulfonyloxy or chloro)-delta 3-cephem with alkenyl halides, e.g., vinyl bromide, trans-1-bromo-1-propene, and trans-beta-bromostyrene in an Al/cat.PbBr2/cat.NiBr2(bpy)/NMP (or DMF) system. Reduction of 3-(trifluoromethylsulfonyloxy)-delta 3-cephem into norcephalosporin was also achieved by a similar reaction in the presence of 5 molar equiv of water. Scope and a plausible mechanism of the Al/Pb/Ni triplemetal-redox promoted reactions are discussed.