Regioselective Synthesis of Coumarin and Quinolone‐Annulated Spiro Heterocycles via Aryl Radical Cyclization

Abstract

3‐(2′‐Bromobenzyloxy)quinolin‐2‐ones and 3‐(2′‐bromobenzyloxy)benzopyran‐7‐ones undergo aryl radical cyclization in the presence of ⁿ Bu₃SnCl‐Na(CN)BH₃‐AIBN to give spiro‐quinolone and coumarin derivatives.

Keywords:

• 5‐Exo‐trig
• organotin reagent
• radical cyclization
• regioselection
• spiro heterocycles

Acknowledgments

We thank the CSIR (New Delhi) for financial assistance. P. P. Mukhopadhyay is grateful to CSIR (New Delhi) for a Senior Research Fellowship. We also thank the DST (New Delhi) for providing the UV‐VIS spectrophotometer and FT‐IR spectrometer under DST‐FIST.