Allene‐Eneyne Related Cycloaromatization: Design and Synthesis of New DNA‐Cleaving Compounds

(Z)-7-Sulfonyl-3-hexen-1,5-diyne containing molecules are stable at room temperature and isomerized to eneyne-allene-sulfones under alkaline conditions. These eneyne-allene-sulfones were not isolable, spontaneously cyclized to form biradical intermediates under mild conditions, and exhibited good DNA-cleaving and human tumor cell line growth inhibition properties. Further studies indicated that compounds bearing on aromatic ring at C(3) and C(4), such as 25, proved to be more active against those tumor cell lines. Removal of acetylene unit at C(1) and C(2), made the resulting compound less active. A related compound, (Z,Z)-12-(2-tetrahydropyranyl)oxy-1-phenylsulfonyldodeca-4,8-diene-2,6,10-triyne (37), was synthesized. Upon treatment of triethylamine at refluxing benzene, this compound undergoes double cycloaromatization to form a naphalene adduct, which possesses excellent DNA-cleaving activity.