Plant coumarins: XI. Cross coupling reactions with 2-(tosyl)oreoselone

The reaction of a linearly fused furocoumarin, oreoselone, with p-toluenesulfonyl chloride gave 2-tosyloreoselone which showed a high reactivity in palladium-catalyzed cross-coupling reactions with formation of a new carbon-carbon bond. 2-Tosyloreoselone reacted with terminal alkynes in the presence of Pd(PPh₃)₂Cl₂ to give the corresponding 2-alkynylfuro3,2-g]chromen-3-ones. 2-Aryl(hetaryl)alkynyloreoselones were obtained in high yield directly by palladium-catalyzed reaction of oreoselone with tosyl chloride and aryl(hetaryl)acetylenes. The reaction of 2-tosyloreoselone with aryl(hetaryl)boronic acids in the presence of palladium complexes with uni- and bidentate ligands, tetrabutylammonium bromide, and a base afforded 2-aryl(hetaryl)-substituted oreoselones. 2-Vinyloreoselone was synthesized from 2-tosyloreoselone and potassium trifluoro(vinyl)borate.