Synthesis of flavones via the Stork-Danheiser reaction.

A new method to access flavones in a convergent fashion has been developed, based on the Stork-Danheiser reaction. By this method, 4-methoxy coumarins are allowed to react with organolithium at low temperatures (-78 °C to -40 °C) and then acidic workup gives the desired flavones in 18-86% yields. This method features transition metal-free conditions, readily available starting materials, and simple operation. It is particularly efficient when rapid generation of B ring flavone derivatives is desired.