Ruthenium complexes carboxylates

Ruthenium complexes have been used in the hydrocarbonylation of simple esters to produce the corresponding homologous esters (50). The hydrocarbonylation affects the alkyl moiety rather than the carboxylate group ... 

In accordance with FMO theory predictions,273 C2 —C4is the preferred modeofcycloaddition of tricarbonyliron and -ruthenium complexes of methyl l//-azepine-l-carboxylate with ethenetetracarbonitrile,222,274 hexafluoroacetone,222 and 2,2-bis(trifluoromethyl)ethene-l,l-dicarbonitrile 222 however, with ethenetetracarbonitrile, tricarbonyl[f/4-l-(ethoxycarbonyl)-1/f-azepine]iron(0) (1) yields a 1 6 mixture of the predicted C2 —C4 exo-adduct 2 and the C2 — C7 [6 + 2] 7i-cycloadduct 3,222 the latter heing formed by rearrangement of the former.274 Mixtures of the two adducts are also obtained with the tricarbonyliron complexes of 3-acetyl-l//-azepine and its l-(ethoxycarbonyl) derivative.274... 

Ruthenium complexes containing this ligand are able to reduce a variety of double bonds with e.e. above 95%. In order to achieve high enantioselectivity, the reactant must show a strong preference for a specific orientation when complexed with the catalyst. This ordinarily requires the presence of a functional group that can coordinate with the metal. The ruthenium-BINAP catalyst has been used successfully with unsaturated amides,23 allylic and homoallylic alcohols,24 and unsaturated carboxylic acids.25... 

ASYMMETRIC HYDROGENATION OF 3-OXO CARBOXYLATES USING BINAP-RUTHENIUM COMPLEXES (R)-(-)-METHYL 3-HYDROXYBUTANOATE (Butanoic acid, 3-hydroxy-, methyl ester, (R)-)... 

Ru-vinylidene complexes can be easily prepared by reaction of low-valent ruthenium complexes with terminal acetylenes. Treatment of the Ru(ii) complex 117 with phenylacetylene gave the Ru(iv)-vinylidene complex 118 in 88% yield (Scheme 41 ).60 The reaction of 118 with C02 in the presence of Et3N afforded selectively the Ru-carboxylate complex 120, probably via the terminal alkynide intermediate 119. 

Ruthenium catalysts have also been used in this context.200,201 In particular, the cationic ruthenium complex, CpRu(CH3CN)3PF6, in conjunction with carboxylic acid ligand 3, has been used to achieve the remarkably chemoselective allylation of a variety of alcohols via dehydrative condensation with allyl alcohol (Equation (50)).202 It is worth noting that this transformation proceeds with 0.05 mol% catalyst loading and does not require the use of excess allyl alcohol. 

BINAP itself has been shown to be effective for the reduction of a,/ -unsatu-rated carboxylic acids [8, 36, 177, 215-220], but Hg-BINAP often provides higher ee-values [193, 194]. The ruthenium complex with P-Phos provides high selectiv-... 

Ruthenium complexes B are stable in the presence of alcohols, amines, or water, even at 60 °C. Olefin metathesis can be realized even in water as solvent, either using ruthenium carbene complexes with water-soluble phosphine ligands [815], or in emulsions. These complexes are also stable in air [584]. No olefination of aldehydes, ketones, or derivatives of carboxylic acids has been observed [582]. During catalysis of olefin metathesis replacement of one phosphine ligand by an olefin can occur [598,809]. 

In a related report, ruthenium-catalyzed enantioselective hydrogenation of 3-keto esters was utilized to prepare the crucial alcohol intermediate 36 (Scheme 14.16). The required (3-keto ester 49 was readily prepared from commercial thiophene carboxylic acid 40. Hydrogenation of 49 then led to the desired (S)-alcohol 50 in quantitative yield and 90% enantiomeric excess, catalyzed by a chiral diphosphine-ruthenium complex generated in situ. Catalyst-substrate ratios used were as low as 1/20,000, rendering this approach amenable to industrial application. Alcohol 50 was then converted to known intermediate 36 in three steps and 60% overall yield. 

DCC activates the carboxyl group for esterification A ruthenium complex is responsible for catalytic ring closure to a macrocyle. 

The stereoselective synthesis of 1,4-disubstituted-l,3-dienes proceeds by head-to-head oxidative coupling of two alkynes with formation of an isolable metallacyclic biscarbene ruthenium complex [23], as shown in Scheme 6. Several key experiments involving labeled reagents and stoichiometric reactions and theoretical studies support the formation of a mixed Fischer-Schrock-type biscarbene complex which undergoes protonation at one carbene carbon atom whereas the other becomes accessible to nucleophilic addition of the carboxylate anion (Scheme 6) [23]. 

In the synthesis of alkylidenecyclobutenes from propargyl alcohols, stoichiometric experiments show that the first step involves [2+2] oxidative head-to-head coupling of the alkynes, leading to an isolable cyclobutadiene-ruthenium complex. Addition of acid generates a cyclobutenyl metal intermediate which undergoes carboxylate addition on the less substituted allylic carbon atom (Scheme 7). 

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