A Highly Active, Heterogeneous Catalyst for Alkyne Metathesis

摘要

Highly active alkyne-metathesis catalysts have been realized by exchanging the amide ligands on molybdenum(VI) alkylidyne trisamide complexes 1 with simple phenols,[1], [2] such as 4-nitrophenol, or by use of chlorotrisamide Mo(IV) complexes.[3] In spite of this practical utility, these catalysts can become deactivated over time, apparently through a bimolecular dimerization pathway.[4] The polymerization of 2-butyne, the metathesis by-product obtained from propynyl substrates,[1a],[b] is another interfering reaction which occurs when the catalytic reaction is preformed at room temperature. Herein, we describe a heterogeneous, alkyne-metathesis catalyst that avoids the use of phenolic ligands. The supported catalyst exhibits very high activity at room temperature while showing exceptional selectivity for catalyzing alkyne metathesis rather than alkyne polymerization, even on a preparative scale.