Hydroalkoxylation-Initiated Cascade on Sulfone-Tethered Aryl Alkynols Gives Cyclic and Spiro-Heterocyclic β-Ketosulfones

Abstract

Serendipitous formation of cyclic β-ketosulfones is observed when sulfone-tethered arylalkynols are reacted with base. The reaction involves a base-promoted propargyl sulfone to the allene isomerization/intramolecular hydroalkoxylation/retro-oxa-Michael/6-endo-trig Michael addition cascade. Sulfone-tethered alkynyl acrylates gave stereoselective access to a diverse array of spirocyclic β-ketosulfone benzofuran/isochroman/indolines and sulfone-tethered bridged bicyclo[3.3.1]nonane. These cyclic βketosulfones could be readily elaborated into benzofuran-fused cyclic sulfones and tetracyclic spiroindoline.

Synthesis of Sulfonyl Arenes via Hydroxy/Amino‐Benzannulation of Sulfonyl Enynals

“…1c). [16] Based on these results, we envisioned that replacing the acceptor acrylate moiety with aldehyde could give access to the bridged bicyclic β-ketosulfone VI. Interestingly, when this reaction was attempted, a serendipitous formation of β-naphthol V was observed, albeit in low yield (Scheme 1, eq.…”