ABSTRACT
Stereoselective synthesis of novel monocyclic trans-3-halogenated-4-pyrazolyl-β-lactams 5 is described. The reaction of ketene derived from α-bromo/chloroethanoic acids 4 using POCl3 and Et3N with pyrazolyl substituted imines 3a–d in refluxing toluene resulted exclusive formation of trans-β-lactams through [2 + 2] through cycloaddition reaction. The chemical structures of all the newly synthesized β-lactams were verified on the basis of spectroscopic techniques such as FTIR, 1H NMR, 13C NMR, and elemental analysis (CHN). The trans configuration of β-lactams 5 was assigned with respect to position of C3-H and C4-H. The novel β-lactams 5 are potential synthons for azetidines, aziridines, 3-unsubstituted azetidinones, 3-alkyl-halo-azetidinones, and promising biologically active agents.
GRAPHICAL ABSTRACT
![](/cms/asset/e73c755c-9a0d-4efd-967d-fb56fa174367/lsyc_a_1371759_uf0001_oc.jpg)
Acknowledgments
Aman Bhalla gratefully acknowledges the financial support for this work from Department of Science and Technology (DST), New Delhi, Government of India, Project No. SR/FT/CS-037/2010 dated 28-10-2010, FIST-II/PURSE-II (DST) and UGC-CAS, Punjab University, Chandigarh. Shiwani Berry acknowledge the financial support from University Grants Commission (UGC) vide sanction No. F1-17.1/2011-12/RGNF-ST-HIM-9284/ (SA-III/ web site) dated 06-06-2012.