Carbocyclization Reaction of Active Methine Compounds with Unactivated Alkenyl or Alkynyl Groups Mediated by TiCl₄−Et₃N

Abstract

In the presence of TiCl 4, Et 3 N, and I 2, iodocarbocyclization reaction of various active methine compounds having alkenyl groups gave iodocycloalkane derivatives in good yields. On the other hand, TiCl 4 and Et 3 N promote the carbocyclization of active methine compounds with 4-alkynyl groups in the absence of I 2 to give methylenecyclopentane derivatives in good yields. This reaction proceeds with high streoselectivity through a cis -addition of trichlorotitanium enolates of active methine compounds to alkynes, and the resulting vinyltitanium intermediates can be further functionalized by the reaction with various electrophiles.