6-Hydroxyaurone aminomethyl derivatives in the inverse electron-demand Diels–Alder reaction

The transformations of 7-dimethylaminomethyl-6-hydroxyaurone and 5-dimethylaminomethyl-6-hydroxy-7-methylurone in the inversed electron-demand hetero-Diels–Alder reaction were studied. As a result of in situ thermal formation of o-quinone methides containing the benzofuranone moiety and cycloaddition of cyclic vinyl esters, 2-benzylidene derivatives of difuro[2,3-b:2',3'-f]chromen-3(2H)-one, furo[2,3-f]pyrano[2,3-b]chromen-3(2H)-one, difuro[2,3-b:3',2'-g]chromen-3(2H)-one, and furo[3,2-g]pyrano[2,3-b]chromen-3(2H)-one heterocyclic systems were synthesized. A similar reaction with cyclic enamines, accompanied by subsequent transformation of hemi-aminals, led to the formation of partially hydrogenated derivatives of furo[2,3-a]xanthen-3(2H)-one and furo[3,2-b]xanthen-3(2H)-one.