Studies on Fused β-Lactams: Synthesis of 1-Aza Analogs of Cephem

Abstract Annelation of 2-methylthio-3,4-dihydropyrimidine (3) with two moles of phenoxyacetyl chloride in presence of triethylamine did not yield the expected β-lactam (6) and instead the N-acylated compound 5a was obtained. Various N-acylated pyrimidines 5a–d also failed to yield any β-lactam. However, β-lactam ring has been conveniently grafted on to 2-methylthio-3,6-dihydropyrimidines 9a–d, 12 by annelating them with in situ prepared aryloxyketenes to furnish novel 1-aza analogs of cephem 10a–e and 13.