First Example of Ionic Liquids-Promoted Domino Knoevenagel Hetero-Diels-Alder Reactions: A Facile Synthesis of Pyrano[3,2-c]coumarins

Abstract

O-Prenylated aromatic aldehydes undergo smooth intramolecular domino Knoevenagel hetero-Diels-Alder reactions with 4-hydroxycoumarins in the air- and moisture-stable ionic liquid [bmim]BF₄ under mild conditions to afford a novel class of cis-annulated pyranocoumarins in high yields. The recovered ionic liquid can be reused in successive runs with consistent activity.

Key words

Diels-Alder reaction - heterodienes - coumarins - cis-annulated polyclic heterocycles

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