Iridium-catalyzed isomerization of primary allylic alcohols under mild reaction conditions

Mantilli, Luca; Mazet, Clément

doi:10.1016/j.tetlet.2009.04.130

Cited by 81 publications

(53 citation statements)

References 37 publications

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“…11 Building on the observation that Crabtree's hydrogenation catalyst [(Cy 3 P)(C 6 H 5 N)Ir(cod)](PF 6 ) 3 may perform unexpected isomerization for certain olefinic substrates, 12 Mazet and coworkers have recently developed a protocol which enables the exclusive isomerization of a variety of primary allylic alcohols into aldehydes under very mild reaction conditions. 13 Molecular hydrogen was used to generate the active form of the catalyst but was extruded from the reaction media prior to addition of the allylic alcohols to prevent competing hydrogenation. Interestingly, the use of the weakly coordinating BAr F anion (BAr F : tetrakis[3,5-bis(trifluoromethyl)phenyl]borate) provided enhanced stability of the precatalyst along with improved catalytic performance.…”

Section: ç Primary Allylic Alcoholsmentioning

confidence: 99%

Platinum Metals in the Catalytic Asymmetric Isomerization of Allylic Alcohols

Mantilli

Mazet

2011

Chemistry Letters

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Past and recent advances in the metal-catalyzed asymmetric isomerization of allylic alcohols into carbonyl compounds are discussed in the present Highlight. Emphasis is placed on rhodium, ruthenium, and iridium; the only three metals that have proven successful to date for this most challenging transformation. Ç IntroductionThe metal-catalyzed asymmetric isomerization of primary and secondary allylic alcohols into the corresponding aldehydes and ketones®a reaction of both academic and industrial relevance®has attracted renewed interest in recent years. 1Because such transformations undergo refunctionalization upon isomerization, they are often described as internal redox processes and from a synthetic viewpoint, legitimately placed at the very top of the atom-economy scale (Scheme 1). 2Although a variety of transition metals displays interesting catalytic activity for the non-asymmetric isomerization of some allylic alcohols with TOF up to 62500, 3 the substrate generality remains a major limitation. In most cases, the catalytic activity tends to decrease as a function of the degree of substitution of the olefinic double bond and thus limits investigation of substrates with a prochiral double bond. Catalysts that are effective for the isomerization of primary allylic alcohols are less active for secondary allylic alcohols as is the converse. Furthermore, the lack of supporting organometallic chemistry and the limited number of thorough mechanistic studies using achiral catalysts constitute severe bottlenecks in the rationalized development of highly active and selective chiral catalysts for the related asymmetric isomerization reactions.The focus of the present Highlight is placed exclusively on chiral catalysts elaborated around rhodium, iridium, and ruthenium, three of the Platinum Metals which have been applied with various success to the asymmetric isomerization of primary and secondary allylic alcohols. Ç Primary Allylic AlcoholsThe asymmetric isomerization of primary allylic alcohols into chiral aldehydes is historically intimately linked to the related isomerization of allylic amines into chiral enamines. 46 The degree of refinement attained by this rhodium-catalyzed process in terms of activity, selectivity, generality, and practicality is exceptional and has helped defining standards of excellence; very few other catalytic asymmetric transformations have reached to date. In contrast, the asymmetric isomerization of allylic alcohols does not belong to this elite category. Because of the apparent similarity between both isomerization reactions, and the influence of the success story of the cationic [(binap)Rh] system for the isomerization of allylic amines, most of the subsequent catalysts have been designed using chiral bidentate phosphines and rhodium for the isomerization of primary allylic alcohols. The initial studies conducted in the early 80s' showed that [(binap)Rh(cod)]ClO 4 1 (cod: 1,5-cyclooctadiene) was also catalytically competent for the isomerization of primary allylic alcohols i...

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Section: ç Primary Allylic Alcoholsmentioning

confidence: 99%

Platinum Metals in the Catalytic Asymmetric Isomerization of Allylic Alcohols

Mantilli

Mazet

2011

Chemistry Letters

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“…We rapidly identified hydrogenation catalysts 1a and 1b (i.e., Crabtree catalysts) to be unique at catalyzing the isomerization of a variety of primary allylic alcohols, including those with a tri‐ or tetrasubstituted olefin moiety 6. The key to obtaining exclusive isomerization was to perform the catalytic experiments under hydrogen‐free conditions after generation of the active dihydride species 1a‐(H) 2 or 1b‐(H) 2 by using molecular hydrogen.…”

Section: Introductionmentioning

confidence: 99%

Structure–Activity Relationship in the Iridium‐Catalyzed Isomerization of Primary Allylic Alcohols

et al. 2012

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The evaluation of a series of cationic iridium complexes in the isomerization of primary allylic alcohols has revealed the unique ability of Crabtree catalysts [(Cy3P)(C6H5N)Ir(cod)]·X 1a (X = PF6) and 1b (X = BArF; cod = 1,5-cyclooctadiene) to catalyze efficiently this transformation. Emphasis has been placed on understanding the electronic factors that govern the catalytic process by using a range of para-substituted pyridine N-donor ligands. Excellent correlations between analytical data (13C NMR chemical shift; νCO) and established thermodynamic and kinetic parameters (pKa, Mayr nucleophilicity parameter N) have been elaborated. Overall, the results obtained point to the possibility of qualitatively predicting the activity of Crabtree catalyst analogues in the isomerization of primary allylic alcohols

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“…The most common catalysts are based on late transition metals such as iridium, rhodium, ruthenium, and palladium. [2][3][4][5][6][7][8][9][10] The dimeric ruthenium complex, [{Ru(p-cymene)Cl 2 } 2 ] is commonly employed as an isomerization catalyst, either on its own or in combination with different ligands and bases. Furthermore, several asymmetric isomerization protocols for the generation of enantiomerically enriched aldehydes and ketones have been developed, in which the stereogenic centers are in close proximity to the newly formed carbonyl functionality.…”

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Ruthenium‐Catalyzed Tandem‐Isomerization/Asymmetric Transfer Hydrogenation of Allylic Alcohols

Slagbrand¹,

Lundberg²,

Adolfsson³

2014

Chemistry A European J

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A one-pot procedure for the direct conversion of racemic allylic alcohols to enantiomerically enriched saturated alcohols is presented. The tandem-isomerization/asymmetric transfer hydrogenation process is efficiently catalyzed by [{Ru(p-cymene)Cl2 }2 ] in combination with the α-amino acid hydroxyamide ligand 1, and performed under mild conditions in a mixture of ethanol and THF. The saturated alcohol products are isolated in good to excellent chemical yields and in enantiomeric excess up to 93 %.

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Iridium-catalyzed isomerization of primary allylic alcohols under mild reaction conditions

Cited by 81 publications

References 37 publications

Platinum Metals in the Catalytic Asymmetric Isomerization of Allylic Alcohols

Platinum Metals in the Catalytic Asymmetric Isomerization of Allylic Alcohols

Structure–Activity Relationship in the Iridium‐Catalyzed Isomerization of Primary Allylic Alcohols

Ruthenium‐Catalyzed Tandem‐Isomerization/Asymmetric Transfer Hydrogenation of Allylic Alcohols

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