Catalytic 2 + 2 + 2 Cycloaddition of Benzothiophene Dioxides with α,ω-Diynes for the Synthesis of Condensed Polycyclic Compounds

A Rh-catalyzed intermolecular 2 + 2 + 2 cycloaddition of the 2,3-double bond of benzothiophene dioxides with α,ω-diynes gave sulfone-containing cycloadducts in high yields. This is the first example of a catalytic 2 + 2 + 2 cycloaddition that uses the 2,3-double bond of a heterole as an ene moiety. The consecutive reaction of benzodithiophene tetraoxide with 2,3-naphthylene-tethered 1,7-diyne gave an 11-ring condensed polycyclic compound in one pot.