Synthesis of pyrano[2,3-]chromen-2-ones pyrano[3,2-]chromen-2-ones through site controlled gold-catalyzed annulations

Regioselective access to 10-substituted-2 H ,8 H -pyrano[2,3- f ]chromen-2-ones through the gold-catalyzed intramolecular hydroarylation of readily available 7-(prop-2-yn-1-yloxy)-2 H -chromen-2-one derivatives at their C-8 congested position was investigated by tuning the electronic and steric properties of the ligand on the gold complex. On the other hand, the combination of the JohnPhosAu(MeCN)SbF 6 catalyzed intramolecular hydroarylation of 8-iodo-7-(prop-2-yn-1-yloxy)- 2H -chromen-2-one derivatives followed by selective palladium/formate C-I reduction allows for the exclusive formation of 2 H ,8 H -pyrano[3,2- g ]chromen-2-one regioisomers. The development of these two protocols provides versatile synthetic tools required for exploring the biological activities of these new pyranocoumarin derivatives. A regioselective intramolecular hydroarylation of 7-(prop-2-yn-1-yloxy)-2 H -chromen-2-one derivatives to afford 10-substituted-2 H ,8 H -pyrano[2,3- f ]chromen-2-ones by means of Au( i ) catalysis.