Synthesis of polycyclic heterocycles via sequential Au-catalyzed cycloisomerization and Ru-catalyzed metathesis reactions

A sequential and efficient catalytic preparation of polycyclic heterocycles, including tetrahydro furo- or cyclopenta- pyran, hexahydropyrano pyrrolidine, and tetrahydroisochromene derivatives is described based on a gold-catalyzed cycloisomerization reaction followed by a Ru-catalyzed ring-closing metathesis. An isomerization of the alkene moiety leading diastereoselectively to cis tetrahydrocyclopenta[c]pyran and tetrahydro-1H-furo[3,4-c]pyran is observed in some cases. The catalytic hydrogenation reactions of these tetrahydropyrans led to the formation of polycyclic-functionalized saturated compounds.