Synthesis of Naphthofuroquinones by a Three-Component Reaction

Significance

A synthesis of naphtho[2,3-b]furan-4,9-diones by a one-pot, three-component reaction of 2-hydroxynaphthalene-1,4-dione, aldehydes, and isonitriles is reported. Both aliphatic aldehydes and aromatic aldehydes bearing EWGs/EDGs and α,β-unsaturated aldehydes underwent coupling with alkyl and vinyl isocyanides to give products in high yields. However, use of aryl isocyanides gave the respective products in less than 20% yields. A mechanism is proposed involving a Knoevenagel-like condensation of 2-hydroxynaphthoquinone with an aldehyde to form an enone intermediate A. A [4+1] cyclization follows leading to the product.