Zinc (II) Chloride as Phase Transfer Catalyst and as Catalyst of Cycloaddition Azide Ion to Heterocumulenes and Terminal Alkynes in Organic Solvents

The system of NaN3-ZnCl2 in organic solvents is effective for azide ion cycloaddition to heterocumulenes and terminal alkynes. The reaction proceeds readily in the case of heterocumulenes, so these transformations fall into the category of click reactions. The study on the reaction mechanism showed that role of zinc salt consists in transferring azide ion to the organic phase and decreasing the energy barrier of nucleophilic addition of azide ion to the unsaturated substrate.