Ruthenium‐Indenylidene Complexes: Scope in Cross‐Metathesis Transformations

Abstract

A comparative study examining the catalytic activity of a series of five indenylidene-containing ruthenium complexes in olefin cross-metathesis reactions is presented. Results reveal the greater efficiency of precatalyst 5, highlighting the key role of the N,N'-bis(2,6-diisopropylphenyl)imidazol-2-ylidene (IPr) ligand for this transformation. The scope of this precatalyst was investigated and several microwave experiments were carried out allowing for catalyst loadings as low as 0.1 mol%. Overall, crossmetathesis products were isolated in moderate to excellent yields with high stereoselectivity.

Cross‐metathesis with acrylonitrile and applications to fatty acid derivatives

“…They reveal that the most efficient catalytic systems are based on relatively high loading of Grubbs-Hoveyda-Blechert catalysts operating with a twofold molar excess of acrylonitrile. On the other hand, ruthe- nium-indenylidene complexes were found to be poor catalysts for this transformation [15]. The cross-metathesis of acrylonitrile with pent-4-en-1-ol to give the C6-nitrile-alcohol, carried out with 5 mol-% of Grubbs-Hoveyda II (4) is concentration dependent and the best yield (74%; Z/E = 2.5 : 1) was obtained in a diluted solution (0.07 M) ( Fig.…”

Mixed Isobutylphobane/N‐Heterocyclic Carbene Ruthenium‐ Indenylidene Complexes: Synthesis and Catalytic Evaluation in Olefin Metathesis Reactions

“…This is in sharp contrast with previous results from the literature that demonstrated the superior activity of second generation ruthenium-benzylidene or indenylidene catalysts based on the PCy 3 ligand, such as 2 or 4, over their first generation counterparts (1 and 3, respectively) in several types of CM reactions. [47,54] This discrepancy further suggests that complexes 10 and 11 are particularly stable in solution and are much slower initiators for olefin metathesis than most ruthenium-alkylidene species investigated so far.…”

Synthesis of Cyclic Peptides and Peptidomimetics by Metathesis Reactions

“…Based on an initial screening [137], ring-closing metathesis of 102a was performed with M1 [140] (30 mol%) and gave 101a in 91% yield, while RCM in the presence of Zhan-1B [141] (10 mol%) resulted in the isolation of 101a in 98% yield. Despite the high yields, high catalyst loading and high dilution conditions (<3 mM) were required.…”