Development of Organocatalytic Darzens Reactions Exploiting the Cyclopropenimine Superbase

A truly organocatalytic approach to the Darzens reaction affording <i>α</i>,<i>β</i>-epoxy carbonyl compounds in good yields was developed taking advantage of the high basic strength and low nucleophilicity of cyclopropenimine superbases. The catalytic active free base can easily be generated in situ from its hydrochloride salt and maintained in the active deprotonated form by performing the reactions in a heterogeneous reaction system in the presence of excess potassium carbonate as a sacrificial base.