Intramolecular Ketone-Olefin Radical Cyclization with Low-Valent Titanium Reagent: Synthesis of Benzopyrans

Abstract

A novel protocol for intramolecular ketyl-olefin radical cyclization with low-valent titanium reagent is outlined. It allows the formation of the benzopyran nucleus from ortho-allyloxy propiophenones as the sole product in moderate yields via intramolecular radical cyclization.

Keywords:

• Benzopyran
• intramolecular radical cyclization
• low-valent titanium reagent
• ortho-allyloxy aromatic aldehydes/ketones

ACKNOWLEDGMENT

One of the authors (S. B.) is thankful to the Department of Atomic Energy, government of India, for financial support in the form of a senior research fellowship.

Notes

^a Isolated yield after column chromatography.