3-Cyanocephems, and carbon-3 heterocyclic-substituted cephems via 1,3-dipolar cycloadditions

The transformation is described of 3-formylcephem 1 into its oxime, substituted oximes, and substituted hydrazones and, thence, into the 3-cyano, 3-diazomethyl, and 3-oxonitrilomethyl derivatives. These reactive 1,3-dipoles undergo 1,3-dipolar cycloadditions with various dipolarophiles to give C-3 heterocyclic-substituted cephems.