Microwave-assisted synthesis of chromeno[3,4-b]xanthones and (benzo[c]cromenyl)chromones

Following previous reports dealing with the reactivity of chromone derivatives in Diels-Alder reactions, series of novel (E)-2-[2-(prop-2-yn-1-yloxy)styryl]chromones and of 2-{(1E,3E)-4-[2- (prop-2-yn-1-yloxy)phenyl]buta-1,3-dien-1-yl}chromones were designed and synthesized through aldol condensation of 2-methylchromones with 2-propargyloxy(benzaldehyde and cinnamaldehyde), respectively. Both chromone derivatives were used as substrates in microwave-assisted intramolecular Diels-Alder reactions, affording chromeno[3,4-b]xanthones and (benzo[c]chromenyl)chromones. This is the first report involving chromone derivatives in intramolecular Diels-Alder reactions for the synthesis of new oxygen heterocycles, namely xanthones and flavones [1-2].
Two series of novel propargyloxychromones were designed and synthesized. Both chromone derivatives were used as substrates in MW-assisted intramolecular Diels-Alder reactions, affording chromeno[3,4-b]xanthones and (benzo[c]chromenyl)chromones. This is the first report involving chromone derivatives in intramolecular Diels-Alder reactions for the synthesis of new oxygen heterocycles, namely xanthones and flavones.

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