Stereoselective synthesis of novel monocyclic trans-3-halogenated-4-pyrazolyl-β-lactams: Potential synthons and promising biologically active agents

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

KEYWORDS:

• β-Lactams
• cycloaddition
• pyrazolyl
• stereoselective
• trans-3-halogenated-4-pyrazolyl-β-lactams

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.

Additional information

Funding

This work was supported by the Department of Science and Technology (DST), New Delhi, Government of India [Grant Number SR/FT/CS-037/2010] and University Grants Commission (UGC), New Delhi, India [Grant Number F1-17.1/2011-12/RGNF-ST-HIM-9284/ (SA-III/ web sit].