Unified Radical Sulfonylative-Annulation of 1,6-Enynols with Sodium Sulfinates: A Modular Synthesis of 2,3-Disubstituted Benzoheteroles

Benzoheteroles are valuable scaffolds in medicinal chemistry,
but
the direct synthesis of 3-vinyl benzoheterole analogues remains unexplored.
A rationally designed new class of 1,6-enyne-containing propargylic
alcohols has been prepared for the modular synthesis of 3-alkenyl
benzoheteroles. Ag-catalyzed cascade radical sulfonylative-cycloannulation
of 1,6-enynols with sodium sulfinates is realized to access a wide
variety of 2,3-disubstituted benzoheteroles in good to high yields.
Moreover, a three-component coupling of 1,6-enynols, aryldiazonium
salts, and Na2S2O5 (as an SO2 surrogate) has been achieved to deliver benzoheterole derivatives
in moderate to good yields. Of note, a scalable reaction and late-stage
synthetic transformations were successfully demonstrated. A plausible
mechanism is also presented based on the existing experimental results
and control experiments.