Enyne Metathesis

Abstract

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Substituent-Enhanced Intermolecular Catalytic Ene-yne Metathesis for Efficient 1,3-Diene Synthesis

“…The most studied catalysts for ene-yne metathesis are based on ruthenium carbenes . We chose to employ the second-generation Hoveyda–Grubbs catalyst 1 to avoid the competing, inhibitory coordination of phosphine ligands, even though fewer studies utilize 1 in ene-yne metathesis reactions compared to other ruthenium carbene catalysts, and nitro-substituted analogues of 1 show higher reactivity in ring-closing ene-yne metathesis .…”

“…As a mild and atom-economical catalytic reaction to create new C–C bonds by combination of alkenes and alkynes, ene-yne metathesis could potentially provide 1,3-dienes at a preparative scale from readily available reactants (see the representative example in Scheme ). Moreover, intramolecular ene-yne metathesis reactions, catalyzed by ruthenium carbenes, efficiently give cyclic 1,3-dienes with high turnovers (TOs = mole product/mole catalyst after a fixed time) and turnover frequencies, good stereo- and regioselectivity for the desired product, and tolerance of Si–O, ester, halide, carboxylic acid, ether, and amine functional groups present in the reactants. − In contrast to these catalytic cyclizations, intermolecular ene-yne metathesis is underdeveloped in the context of sustainable syntheses of dienes. High catalyst loading (2.5–10 mol %), often required to overcome low yields and catalyst decomposition, leads to low TOs and inefficient use of the precious ruthenium catalyst, limiting larger-scale preparations. − The requirement of high catalyst loading may be exacerbated by reactive moieties such as peroxides, resulting in seemingly poorer tolerance of some functional groups .…”

Application of Olefin Metathesis in the Synthesis of Carbo- and Heteroaromatic Compounds—Recent Advances

“…EYCM may also be used for the synthesis of 1,3-dienes. Although the reaction can lead to the formation of stereo- and regioisomers, a number of examples of the selective course of the reaction have been described [ 19 , 20 , 21 ]. Cross-metathesis between a 1-alkene and a 1-alkyne leads to 1,3-substituted 1,3-dienes, as shown in Scheme 4 .…”

Editorial of Special Issue Ruthenium Complex: The Expanding Chemistry of the Ruthenium Complexes

“…Among metathesis reactions, cross-metathesis (CM) [246,247,248,249] and ring-closing metathesis (RCM) [250,251,252,253,254] have become the most encountered strategies for the synthesis of linear and branched, or carbocyclic and heterocyclic compounds. Ru-catalyzed enyne metathesis (EYRCM) provided an elegant and productive way to obtain small, medium and large cyclic molecules [255]. Numerous tandem metathesis protocols (RCM-CM, RCM-RCM, and RCM-ROM-CM), as well as related processes (C–C coupling, cyclopropanation, cyclizations, and polymerizations) facilitated the synthesis of complex organic molecules, intermediates for fine chemicals, bioactive natural products, macrocyclic or polycyclic structures, functional polymers and supramolecular architectures [256,257,258,259,260,261,262,263,264].…”