Studies on Sequential Claisen Rearrangement: Charge‐Accelerated [3,3]‐Sigmatropic Rearrangement Leading to Polyheterocycles

Abstract

A number of quinolone‐annulated pentacycles have been regioselectively synthesized in 90–95% yields by sequential Claisen rearrangements. The second synthesis is anhydrous AlCl₃‐catalyzed charge‐accelerated aromatic Claisen rearrangement of 1‐aryloxymethyl‐6‐alkyl‐3H‐pyrano[2,3‐c]quinolin‐5(6H)‐ones in dichloromethane at rt for 5–10 min. The precursors were synthesized by the thermal [3,3]‐sigmatropic rearrangement of the corresponding ethers.

Keywords:

• anhydrous aluminium chloride
• Lewis acid–catalyzed Claisen rearrangement
• polyheterocycles
• quinolone derivatives

Acknowledgment

We thank the Council of Scientific and Industrial Research (CSIR) (New Delhi) for financial assistance. Two of us (D. S. and P. D.) are grateful to the CSIR for senior research fellowships. We also thank the Department of Science and Technology (DST) (New Delhi) for providing UV‐vis and IR spectrometers under the DST‐Financial Assistance for Infrastructural Development of Science and Technology (FIST) Program.