Halo-1,2,3-triazolium Salts as Halogen Bond Donors for the Activation of Imines in Dihydropyridinone Synthesis

In
the past decade halogen bond (XB) catalysis has gained considerable
attention. Halo-triazoles are known XB donors, yet few examples detail
their use as catalysts. As a continuation of our previous work the
catalytic properties of substituted enantiomerically pure halo-triazolium
salts were explored in the reaction between an imine and Danishefsky’s
diene leading to the formation of dihydropyridinone. The catalytic
activity of the XB donors was highly dependent on the choice of the
halogen atom and on the counterion. Also, it was found that impurities
in the diene affected the rate of the reaction.