Highly Regio- and Stereoselective Synthesis of Tetrasubstituted Cyclobutenes via Cyclodimerization of Alkynes Mediated by Zirconium

Zirconium-induced cyclodimerization of a variety of heteroaryl-substituted alkynes is described. This method provides a facile synthesis of tetrasubstituted cyclobutenes with high regio- and diastereoselectivity. A ligand-induced reductive elimination mechanism accounting for this novel cyclodimerization is suggested.