Copper-catalyzed cascade cyclization reaction of 3-aminocyclobutenones with electron-deficient internal alkynes: synthesis of fully substituted indoles.

A novel copper-catalyzed cascade cyclization reaction of 3-aminocyclobutenones with electron-deficient internal alkynes has been developed for the first time. This reaction provides a new and highly efficient method for the synthesis of fully substituted indoles by formation of four new bonds and two rings from readily available starting materials in a single step.