Hetero Diels–Alder Cycloaddition of Indene for the Formal Synthesis of Onychnine

Abstract

A highly regio‐ and stereoselective hetero Diels–Alder cycloaddition of indene with N‐sulfonyl‐1‐aza‐1,3‐butadiene was achieved. Subsequent transformation of the 5H‐indeno [l,2‐b]pyridine via elimination and reduction provides a new route to azafluorenone (e.g., 1‐methyl‐4‐azafluorene) for the synthesis of onychnine.

Keywords:

• Azafluorenone
• cycloaddition
• Diels–Alder
• onychnine
• regioselective synthesis

Acknowledgments

Financial support from the National Science Council, Taiwan, R.O.C. is gratefully acknowledged. Supporting information available: X‐ray cif file for compound 4.