[2+2+2] cycloaddition of sulfanylbenzene-tethered diynes with alkynes for the synthesis of multi-substituted dibenzothiophene derivatives

An intermolecular [2+2+2] cycloaddition of sulfanyl- and sulfonylbenzene-tethered 1,6-diynes with alkynes using rhodium catalysts gave dibenzothiophene derivatives in moderate to excellent yields. The consecutive reaction of tetraynes with an alkyne gave an axially chiral 1,1′-bi(dibenzothiophenyl) and its tetraoxide with up to excellent ee.