Cyclopropyl carbenoid insertion into alkenylzirconocenes—a convergent synthesis of alkenylcyclopropanes and alkylidenecyclopropanes

The insertion of cyclopropyl carbenoids into alkenylzirconocenes, derived by hydrozirconation of terminal alkynes, affords allylzirconium species which react with protons and isonitriles to afford alkenylcyclopropanes, and with aldehydes to afford alkylidene cyclopropanes. The addition of lithium carbenoid to zirconium occurs with the inversion of the organolithium centre.