SynergisticPd/Ag-Catalyzed Domino Reaction: Accessto Tetrahydropyrano[4,3‑<i>c</i>]pyran and Hexahydrofuro[2,3‑<i>b</i>]pyran

We report the Pd-catalyzed and Ag-mediated temperature-dependent divergent synthesis of tetrahydropyrano[4,3-<i>c</i>]pyran and hexahydrofuro[2,3-<i>b</i>]pyran derivatives from a single substrate, alkynols. The reaction involves homocoupling of alkynols to form two C–O bonds and one C–C bond, resulting in tetrahydropyrano[4,3-<i>c</i>]pyran cores at a high temperature (110 °C). Exposing tetrahydropyrano[4,3-<i>c</i>]pyrans to a 200 W tungsten filament bulb yields tetrahydrofuro[2,3-<i>b</i>]pyrans. At lower temperatures (30–60 °C), alkynols produce hexahydrofuro[2,3-<i>b</i>]pyrans. The density functional theory study explains temperature-dependent selectivity.