Syntheses based on 1,2-secopenicillins. Part III. Hydration of 4-(3-substituted prop-2-ynylthio)azetidin-2-ones and a new cephalosporin synthesis

Abstract

Addition of secondary amines to the triple bond of 4-(3-substituted prop-2-ynylthio)azetidin-2-ones or the derived sulphoxides, followed by very ready hydrolysis of the resulting enamines, provides a convenient route to the corresponding β-oxo-sulphides and -sulphoxides. Generation of the carbonyl group in this way, followed by an intramolecular Wittig reaction to close the dihydrothiazine ring, leads to a new synthesis of cephalosporins, illustrated by the preparation of an antibacterially active isostere of cephaloridine.