Tandem cyclization and aromatization of sulfur bridged diallenic systems: Potential enediyne models

The synthesis and base catalyzed rearrangement of bis-gamma-phenylpropargyl sulfone, sulfoxide and sulfonium salts are described. In contrast to the f irst two compounds which undergo a fast acetylene to allene isomerization f ollowed by a tandem cyclization and aromatization via a diradical mechanism ,the latter compound undergoes a [2,3]-sigmatropic shift via the correspond ing ylide intermediate.