Divergent Synthesis of Heterotricyclic Compounds from γ-Alkynyl-1,3-diketones via Base-Mediated Tandem Annulations.

This paper presents a novel base-mediated strategy for the divergent synthesis of oxygen- and nitrogen-containing heterotricyclic compounds, furo[3,2-c]chromene and furo[3,2-c]quinolone, from γ-alkynyl 1,3-diketones without the use of transition metals. These one-pot tandem reaction methodologies demonstrate remarkable versatility, enabling base-mediated O-attack via 5-exo-dig or C-attack intramolecular cyclization onto the alkyne, leading to the formation of furo[3,2-c]chromene or xanthone products. Additionally, sequential reactions involving regioselective condensation followed by tandem annulation afford furo[3,2-c]quinolone. These approaches leverage precisely controlled reaction conditions to direct selective annulation pathways, facilitating the construction of diverse heterocyclic frameworks with significant pharmaceutical potential.