Tandem rearrangement, cyclization and aromatization of sulfur bridged propargylic systems

The reactivity of some novel π-conjugated bis-propargylic sulfides, sulfoxides and sulfones under basic conditions has been investigated. These compounds undergo isomerization to the corresponding diallenes, followed by a tandem cyclization and aromatization of the latter via a diradical intermediate. Surprisingly, we have found that the rate of the cyclization step was independent of the nature of the bridging functionality.