Ruthenium complexes Trienes

In 2008, Grisi et al. reported three ruthenium complexes 65-67 bearing chiral, symmetrical monodentate NHC ligands with two iV-(S)-phenylethyl side chains [74] (Fig. 3.26). Three different types of backbones were incorporated into the AT-heterocyclic moiety of the ligands. When achiral triene 57 was treated with catalysts 65-67 under identical reaction conditions, a dramatic difference was observed. As expected, the absence of backbone chirality in complex 65 makes it completely inefficient for inducing enantioselectivity in the formation of 58. Similarly, the mismatched chiral backbone framework of complex 66 was not able to promote asymmetric RCM of 57. In contrast, appreciable albeit low selectivity (33% ee) was observed when the backbone possessed anti stereochemistry. 

The moderate Lewis acidity of ruthenium complexes was used to promote catalytic Diels Alder reactions, and notably, enantioselective Diels Alder reactions were performed with ruthenium containing a cyclopentadienyl or indenyl ligand and a chiral P,P-ligand such as (/ )-BINOP-F or 1,2-bis(diphenylphosphinamino) cyclohexane [128-132]. These mild chiral Lewis acids proved to be excellent catalysts for the intermolecular Diels Alder reactions of dienes with acrolein derivatives [128-130] [Eq. (61)] and enones [131] as well as for the intramolecular Diels Alder reaction of suitable trienes [132] [Eq. (62)]. 

The structure shown for the bis-jr-allylic complex 2.8, is supported by the structure found by X-ray analysis [55] of the ruthenium complex, 2.9 [55a], which contains the same dodeca-2,6,10-triene-l,12-diyl ligand. 

Grubbs synthesized ruthenium carbene complex 104a, and a high enantiomeric excess (up to 90%) was observed in the desymmetrization of prochiral trienes 80c ... 

The working mechanism involves a [2 + 2] cycloaddition between the Ru=C bond of ruthenium vinylidene and olefin to form the metallacyclobutane 92, which subsequently undergoes P-hydride elimination leading to the 7i-allyl hydride complex 93 and reductive elimination to furnish the conjugated trienes 89 (Scheme 6.31), and eventually to give the observed aromatic product 90. 

Trienes 39 can be converted into tricyclic compounds having an aromatic ring using Ic (Scheme 13). Triple reaction of three alkynes with ruthenium-carbene complexes finally forms the tricyclic aromatic ring. 

If cycloalkene-yne 65 having an o -alkynyl substituent at an olefinic position in a cycloalkene is treated with a ruthenium catalyst, what kinds of products are produced. In this reaction, ruthenium mono-substituted carbene complex XVII is anticipated to be formed from a highly strained ruthenacyclobutane intermediate. If it then reacts with ethylene, triene 67 should be formed, but if XVII reacts with an alkene part intramolecularly, bicyclic compound 66 should be formed via ruthenacyclobutane (Scheme 23). 

Enynes containing a cycloalkene moiety can lead, in the presence of another olefin and a catalytic amount of ruthenium carbene complex, to ringopening and ring-closing metathesis (ROM-RCM) followed by cross metathesis (CM) to produce trienes (Scheme 7). 

Polymeric-ruthenium catalysts have been prepared by the reaction of ( / -cyclo-octa-l,3,5-triene) (// -cycloocta-1,5-diene) ruthenium(0), (// -cydoocta-l,3,5-triene) (COT) (// -cycloocta-1,5-diene) (COD) with polystyrene in hydrogen at room temperature [258]. Elemental analysis, IR and mass-spectrometry data show that in these polymer-metal complexes, two cycloolefin ligands, present in the starting Ru(COT)(COD) complex, are substituted by two phenyl rings of polystyrene ... 

Gold chloride forms an unstable complex with cyclo-octatetraene at low temperatures. This decomposes at — 20°C to l,2-dichlorocyclo-octa-3,5,7-triene, which gradually cyclizes to (562). In an attempt to form pentalene-metal complexes, cyclo-octatetraene was reduced to a mixture of trienes and bicyclo [4,2,0] octadiene, which was then treated with substituent ruthenium carbonyls, affording a variety of complexes, including (563). °... 

Treatment of 5,8-bis(trimethylsilyl)cyclo-octa-l,3,6-triene or 3,5,8-tris(trimethyl-silyl)cyclo-octa-l,3,6-triene with triruthenium dodecacarbonyl gave the pentalene complexes (352 X = H or SiMe ). Tricarbonyl(Ti-cyclo-octa-l,5-diene)ruthenium and tricarbonyl(T)-cyclo-octa-l,3-diene)osmium have been prepared. They react with trityl fluoroborate to give cyclo-octadienylium complexes [(CgHn)M(CO)3] which react with anionic nucleophiles to give neutral compounds, some of which... 

Ruthenium, germanium, and nickel complexes of cyclododeca-l,5,9-triene are reported. 

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