Abstract
Stereoselective synthesis of novel monocyclic trans-3-halogenated-4-pyrazolyl--lactams 5 is described. The reaction of ketene derived from -bromo/chloroethanoic acids 4 using POCl3 and Et3N with pyrazolyl substituted imines 3a-d in refluxing toluene resulted exclusive formation of trans--lactams through [2+2] through cycloaddition reaction. The chemical structures of all the newly synthesized -lactams were verified on the basis of spectroscopic techniques such as FTIR, H-1 NMR, C-13 NMR, and elemental analysis (CHN). The trans configuration of -lactams 5 was assigned with respect to position of C3-H and C4-H. The novel -lactams 5 are potential synthons for azetidines, aziridines, 3-unsubstituted azetidinones, 3-alkyl-halo-azetidinones, and promising biologically active agents.
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