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-<i>oxa</i>-Michael/6-<i>endo</i>-<i>trig</i> 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 β-ketosulfones could be readily elaborated into benzofuran-fused cyclic sulfones and tetracyclic spiroindoline.