Triynes R-C≡C-CH2CH2-Ar-C≡C-Ar'-CH2CH2-C≡C-R were subjected to Co(I)- or Ni(0)-mediated intramolecular [2+2+2] cycloisomerization to provide corresponding tetrahydropentahelicene, tetrahydrohexahelicene, and tetrahydroheptahelicene in good to moderate yields. The reaction tolerates various substituents at pendant acetylene moieties (R = H, CH3, trimethylsilyl, not triisopropylsilyl) and fluorine in an aromatic part. By contrast, under Rh(I) or Pd(0) catalysis, triyne with the CH2OCH2 tether lost pendant propargyl moieties and an aromatic spiroketal was formed preferentially.
Triynes R-C≡C-CH2CH2-Ar-C≡C-Ar'-CH2CH2-C≡C-R经过Co(I)-或Ni(0)-介导的分子内[2+2+2]环异构化反应,产生相应的四氢五环螺花烯、四氢六环螺花烯和四氢七环螺花烯,收率良好至适中。该反应容忍在侧链
乙炔基团上具有各种取代基(R = H、
CH3、三甲基
硅基,但不是
三异丙基硅基)和芳香部分中的
氟原子。相比之下,在Rh(I)或Pd(0)催化下,带有CH2OCH2连接基的三炔失去了侧链
丙炔基团,优先形成了芳香螺环
缩酮。