Cu-modified hydroxy-apatite as catalyst for Glaser–Hay C[sbnd]C homo- coupling reaction of terminal alkynes

Abstract

The oxidative Glaser–Hay coupling reaction of terminal alkynes is a very important reaction in organic chemistry to achieve the synthesis of diyne compounds. In general the reaction is performed under homogeneous conditions using Cu(I) or Cu(II) salts in the presence of a reagent such as tetramethylethylenediamine (TMEDA), which can bind to copper ions, an organic base and dioxygen. Although this reaction is known for a long time, the mechanism is still under discussion. Pursuing our investigations on the use of apatites as catalysts for organic reactions we highlight in this work how it is possible to catalyze the Glaser–Hay reaction under heterogeneous conditions using a Cu-modified hydroxyapatite (Cu–HAp). With several para-substituted phenyl-acetylenes and alkynols we show that Cu–HAp acts as catalyst for CC coupling reactions leading to diyne derivatives in high yields without using auxiliary chelating molecules and organic bases. These heterogeneous conditions allow an easy recovery of the catalyst and simplify the purification work-up.