Carbon–carbon bond forming reactions of N-bound transition metal α-cyanocarbanions: a mechanistic probe for catalytic Michael reactions of nitriles

Tannna, Akio; Murahashi, Shun‐Ichi

doi:10.1039/b007517p

Cited by 27 publications

(14 citation statements)

References 15 publications

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“…[103] However, the reactions of the aryl palladium cyanoalkyl intermediate that would be formed in the conventional catalytic cycle is not well known, and there are a number of possible bonding modes: The anions of nitriles can coordinate to a metal center through the a carbon atom [104] or through the cyano nitrogen atom. [105] Alternatively, the anion can bridge two metal centers to form a h 2 -CN system. [106] Nitriles are also less acidic than ketones, but the cyano group is more electron withdrawing than a keto group, which could lead to unpredictable effects during catalysis, such as complications in the reductive elimination step.…”

Section: A-arylation Of Nitrilesmentioning

confidence: 99%

Metal‐Catalyzed α‐Arylation of Carbonyl and Related Molecules: Novel Trends in CC Bond Formation by CH Bond Functionalization

2010

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Alpha-arylated carbonyl compounds are commonly occurring motifs in biologically interesting molecules and are therefore of high interest to the pharmaceutical industry. Conventional procedures for their synthesis often result in complications in scale-up, such as the use of stoichiometric amounts of toxic reagents and harsh reaction conditions. Over the last decade, significant efforts have been directed towards the development of metal-catalyzed alpha-arylations of carbonyl compounds as an alternative synthetic approach that operates under milder conditions. This Review summarizes the developments in this area to date, with a focus on how the substrate scope has been expanded through selection of the most appropriate synthetic method, such as the careful choice of ligands, precatalysts, bases, and reaction conditions.

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Section: A-arylation Of Nitrilesmentioning

confidence: 99%

Metal‐Catalyzed α‐Arylation of Carbonyl and Related Molecules: Novel Trends in CC Bond Formation by CH Bond Functionalization

2010

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“…The reaction of ethyl cyanoacetate 3d and 2a gave a 1:1 adduct in 22% yield and with low ee in addition to the 2:1 adduct as a major product (52% yield) probably due to the strong interaction of the CN group with the Ru metal [11]. It should be noted that acetylacetone 3e was far less enantioselective although highly reactive, possibly because acetylacetone has favored the chelating enolate formation, resulting in the replacement of the chiral diamine ligand.…”

Section: Resultsmentioning

confidence: 95%

Asymmetric Michael reactions of α-substituted acetates with cyclic enones catalyzed by multifunctional chiral Ru amido complexes

Ikariya

Wang

Watanabe

et al. 2004

Journal of Organometallic Chemistry

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“…Multicomponent reactions that involve three or more substrates provide useful strategy not only for combinatorial chemistry but also for minimizing energy, cost, and chemical waste. We found that IrH 5 (P-i-Pr 3 ) 2 (14) is an effective ambiphilic catalyst, and multicomponent reactions can be performed in one-pot under neutral conditions. Actually, treatment of a mixture of ethyl 2-cyanopropanoate (20), acrylonitrile, and water in THF in the presence of catalyst 14 in a sealed tube at 150 °C gave 2-methylglutarimide (21, 98%), which is an important building block for biologically active substances (eq.…”

Section: Lewis Acid-base Ambiphilic Catalystsmentioning

confidence: 99%

“…Recently, we discovered that iridium hydride complexes IrH(CO)(PPh 3 ) 3 (13) and IrH 5 (P-i-Pr 3 ) 2 (14) can be used as ambiphilic catalysts that work as both Lewis acid and base catalysts. Activation of the α-C-H bonds and the CN triple bonds of nitriles occurs at the same time, and hence cross-addition of nitriles can be performed under neutral conditions to give the corresponding cyanoenamines, which are versatile synthetic intermediates (eq.…”

Section: Lewis Acid-base Ambiphilic Catalystsmentioning

confidence: 99%

“…This discovery leads to find a family of catalytic carbon-carbon bondforming reaction of nitriles with electrophiles [13]. The reaction can be rationalized by assuming the mechanism that involves α-C-H activation of nitriles to give C-bonded complex [RCH(CN)RuH] which undergoes isomerization to N-bonded complex (RC -HCN → Ru + H) and subsequent reaction with electrophiles such as carbonyl compounds and alkenes [14]. Actually, we succeeded in isolation of the C-bound isomer RuCp[CH(CN)SO 2 Ph](PR 3 ) 2 and the N-bound isomer Ru + Cp(NCC -HSO 2 Ph)(PR 3 ) 2 .…”

Section: Redox Base Catalystsmentioning

confidence: 99%

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Ruthenium catalysis in organic synthesis

Murahashi

Takaya

Naota

2002

Pure and Applied Chemistry

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Ruthenium, rhodium, iridium, and rhenium hydride complexes are highly useful redox Lewis acid and base catalysts. Various substrates bearing hetero atoms are activated by these catalysts and undergo reactions with either nucleophiles or electrophiles under neutral conditions. These types of catalytic reactions are described together with their application to the preparation of various biologically active compounds.Ruthenium has various valencies (0 to 8 valene) and is not so expensive transition metal; therefore, various useful catalytic reactions for organic synthesis have been explored [1]. It is noteworthy that the medical property of ruthenium is now being recognized, and ruthenium anticancer agents have recently entered the clinic, showing promising activity on resistant tumors. We have developed various ruthenium-catalyzed reactions. Among them, I would like to focus on our findings that low-valent ruthenium hydride complexes can be used as alternatives to the conventional Lewis acids and bases. Furthermore, using iridium, rhodium, and rhenium hydride complexes, various novel and unique catalytic reactions can be explored.Reactions promoted by Lewis acids and bases are fundamental in organic synthesis; however, most such reactions are merely stoichiometric. Therefore, the development of catalytic reactions that use transition-metal complex catalysts under neutral and mild reaction conditions is particularly important; society needs forward-looking technology, which is based on environmental acceptability. The criteria include atom efficiency, formation of little inorganic waste, and selective synthesis of desired products. We should use instead environmentally friendly catalytic processes that will not produce such waste. If one could design Lewis acid and base catalysts with low redox potentials, their reactions would occur catalytically under neutral conditions. We have, therefore, been searching for transitionmetal complex catalysts, which we call redox Lewis acid and base catalysts [2]. We found that divalent ruthenium hydride complexes act as redox Lewis acid catalysts and also as redox base catalysts. Generation of carbon nucleophiles from pronucleophiles by activation of the α-C-H bond adjacent to hetero atoms followed by reaction with various electrophiles affords catalytic carbon-carbon bond forming reactions under neutral and mild reaction conditions. In principle, conventional acids and bases cannot be used at the same time because of neutralization; therefore, we developed Lewis acid base ambiphilic catalysts which can be utilized as either Lewis acid or bases in one-pot reaction. Low-valent ruthenium, iridium, rhodium, and rhenium hydride catalysts can be used as catalysts to replace both Lewis acids and strong bases, and they can be used in combinatorial chemistry.

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Carbon–carbon bond forming reactions of N-bound transition metal α-cyanocarbanions: a mechanistic probe for catalytic Michael reactions of nitriles

Cited by 27 publications

References 15 publications

Metal‐Catalyzed α‐Arylation of Carbonyl and Related Molecules: Novel Trends in CC Bond Formation by CH Bond Functionalization

Metal‐Catalyzed α‐Arylation of Carbonyl and Related Molecules: Novel Trends in CC Bond Formation by CH Bond Functionalization

Asymmetric Michael reactions of α-substituted acetates with cyclic enones catalyzed by multifunctional chiral Ru amido complexes

Ruthenium catalysis in organic synthesis

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