Tandem sigmatropic rearrangements and cyclizations of propargylic dialkoxy disulfides

The first successful preparation of propargylic dialkoxy disulfides in high yields is reported. These esters afforded novel 6,7-dithiabicyclo[3.1.1]heptane-2-one 6-oxide derivatives via an unprecedented sequence of three [2,3]- and one [3,3]-sigmatropic shifts followed by an intramolecular [2+2] cycloaddition. The latter are structurally related to the zwiebelanes, recently isolated from freshly cut onion.