Well‐Defined Alkyne Metathesis Catalysts: Developments and Recent Applications

Abstract

Although alkyne metathesis has been known for 50 years, rapid progress in this field has mostly occurred during the last two decades. In this article, the development of several highly efficient andt horoughly studied alkyne metathesis catalysts is reviewed, which includes novel welldefined, in situ formed and heterogeneous systems. Various alkyne metathesis methodologies, including alkyne crossmetathesis (ACM), ring-closing alkyne metathesis (RCAM), cy-clooligomerization,a cyclic diyne metathesis polymerization (ADIMET), and ring-opening alkyne metathesis polymerization (ROAMP), are presented, and their application in natural product synthesis, materials science as well as supramolecular and polymer chemistry is discussed. Recent progress in the metathesis of diynes is also summarized, which gave rise to new methods such as ring-closing diyne metathesis (RCDM)a nd diyne cross-metathesis(DYCM). Scheme1.Mechanism of alkyne metathesis.Scheme2.Synthesis of Schrock's tungsten alkylidyne complex 3.[a] H. Ehrhorn, Prof. Dr.M.T amm Scheme9.Synthesis of molybdenumb enzylidynecomplexes 22 with triphenylsilanolate ligands ;phen = 1,10-phenanthroline.Scheme10. Synthesis of trisilanolate tungsten and molybdenum benzylidyne complexes 25.

Isolation of a Homoleptic Non-oxo Mo(V) Alkoxide Complex: Synthesis, Structure, and Electronic Properties of Penta-tert-Butoxymolybdenum

“…For their high activity and excellent functional group tolerance, molybdenum alkylidynes of the general type [(R 1 O) 3 Mo≡CR 2 ] arguably define the state-of-the-art in alkyne metathesis. 30 − 32 Several independent entries into this privileged class of organometallic catalysts have been developed over the years. 33 − 39 One of them employs Mo[N( t -Bu)(Ar)] 3 40 derived from [MoCl 3 (THF) 3 ], which in turn is formed by stepwise reduction of MoCl 5 with MeCN to give [MoCl 4 (MeCN) 2 ], followed by ligand exchange and further reduction of the resulting complex [MoCl 4 (THF) 2 ] with coarse tin.…”

183W NMR Spectroscopy Guides the Search for Tungsten Alkylidyne Catalysts for Alkyne Metathesis

“…Molybdenum alkylidyne complexes endowed with triarylsilanolate ligands such as 1, the corresponding ate-complex 2 and the derived bench-stable phenanthroline adduct [1•-(phen)] set the standards in the field of alkyne metathesis (Figure 1). [1][2][3][4][5] Their functional group compatibility is largely unrivaled; [6][7][8][9][10] it has recently been further improved by the development of a second catalyst generation distinguished by a tripodal silanolate ligand framework. [11,12] Specifically, the "canopy complex" 3 and relatives maintain the virtues of the parent complex 1, yet allow the chelate effect to be harnessed in form of an improved stability towards protic sites; in conjunction with the well-balanced electrophilic character and proper steric protection of the operative Mo CR unit, this results in an excellent overall application profile.…”

Catalytic Asymmetric Total Synthesis of Macrocyclic Marine Natural Product (–)‐Haliclonin A†

“…We envisioned the formation of the Z ‐olefinic bond at C16‐C17 and thus the 15‐membered ring by a macrocyclic ring‐closing alkyne metathesis (RCAM) [ 19 ] followed by a stereoselective Lindlar reduction. Fürstner [ 19 ] extensively explored the chemistry of RCAM from catalysts to reactions and its applications in the total synthesis of natural products. Next, after a retro‐aldol disconnection of the side chain connected at C1, we anticipated the formation of the saturated 17‐membered macrocycle by a ring‐closing metathesis (RCM); [ 20 ] a methodology widely used for the construction of macrocycles.…”