Synthesis of 5-hydroxy-2-(naphth-2-yl)chromone derivatives

The Diels-Alder reaction of 5-hydroxy-2-styrylchromones with ortho-benzoquinodimethane, generated in situ by thermal extrusion of sulfur dioxide from 1,3-dihydrobenzo[c]thiophene 2,2-dioxide, leads to 2(3-aryl-1,2,3,4-tetrahydronaphth-2-yl)-5-hydroxychromones. These cycloadducts were dehydrogenated with DDQ, using classical thermal reflux conditions and microwave irradiation, affording the corresponding 2-(3-arylnaphth-2-yl)-5-hydroxychromones in high yields (48-96%).