Dimerization strategies for the synthesis of high-order securinega alkaloids

Abstract

I describe different modes of dimerization of various $\alpha’$,$\gamma$-dioxyenone derivatives with potential applications to the synthesis of high-order securinega alkaloids. I learned that the relative stereochemical relationship between $\alpha’$ - and $\gamma$- hydroxyl groups of the $\alpha’$,$\gamma$-dihydroxyenone derivative determines the mode of dimerization. While cis-$\alpha’$,$\gamma$-dioxyenone 36 provided Rauhut–Currier-type (RC-type) dimer 42 upon reaction with TBAF, trans-$\alpha’$,$\gamma$-dihydroxyenone 53 afforded dimeric tetrahydrofuran derivative 54 under the same reaction conditions. We also noticed that the protection of the \gamma$- hydroxyl group drastically changes the reaction outcomes. While cis-$\alpha’$-oxy-$\gamma$-OPiv-enone 70 did not show any reactivity in the presence of TBAF, trans-$\alpha’$ -hydroxy-$\gamma$-OPiv-enone 67 produced RC-type dimer 68 under the same reaction conditions. Computational analysis revealed the detailed mechanism of the latter transformation.