Stereoselective synthesis, spectroscopic and X-ray crystallographic characterization of novel trans- and cis-3-methylseleno substituted monocyclic β-lactams: Potential synthons for C-3 functionalized/bicyclic/halospiroseleno-β-lactams of medicinal interest

Abstract

Abstract New series of trans- and cis-3-methylseleno substituted β-lactams (4, 5) have been prepared from 2-methylselenoethanoic acid (2). The four-membered β-lactam ring was introduced by the condensation reaction between ketene retrieved from 2-methylselenoethanoic acid (2) and suitably substituted imines (3a-f) in the presence of triethylamine using POCl3 in refluxing toluene. The structural and stereochemical analysis of novel trans- and cis-3-methylseleno substituted β-lactams were carried out using IR, NMR (1H and 13C), 2D-NMR (1H–1H COSY, 1H–13C HSQC), elemental analysis (CHN) and mass spectrometry (EIMS). Further, the structures of trans-1-(4′-methoxyphenyl)-3-methylseleno-4-(4′-chlorophenyl)azetidin-2-one (4b), trans-1-(4′-methoxyphenyl)-3-methylseleno-4-(4′-methylphenyl)azetidin-2-one (4c), trans- and cis-1-(4′-methoxyphenyl)-3-methylseleno-4-styrylazetidin-2-ones (4e and 5e) were established by single crystal X-ray crystallographic studies. The cis or trans configuration of the hydrogen at C-3 was assigned with respect to C4-H.