Chiral ruthenium complexes as catalysts in enantioselective Diels–Alder reactions. Crystal structure of the Lewis acid–dienophile adduct

Carmona, Daniel; Elipe, Sergio; Lahoz, Fernando J.; Oro, Luis A.; Cativiela, Carlos; Víu, M. Pilar López-Ram de; Lamata, M. Pilar; Vega, Cristina; Viguri, Fernando

doi:10.1039/a705605b

Cited by 87 publications

(47 citation statements)

References 11 publications

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“…[114] Areneruthenium complexes with chiral metal atoms and optically active chelating ligands were also used successfully as enantioselective catalysts in Diels ± Alder reactions. [112,113,127] Although the diastereomer equilibrium 31 a > 31 b is established for complex 31 under the conditions of the olefin isomerization (20 8C, 24 h), such equilibria are, as mentioned, strongly shifted to one side. How the configurationally favored and disfavored diastereomers contribute to the enantioselectivity of the catalytic olefin isomerization and how the two diastereomers differ in their reactivities are yet to be explained.…”

Section: Complexes With Chiral Metal Atoms In Enantioselective Catalysismentioning

confidence: 86%

Optically Active Organometallic Compounds of Transition Elements with Chiral Metal Atoms

Brunner¹

1999

Angew. Chem. Int. Ed.

323

144

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Chiral transition metal atoms are not only present in tris-chelate complexes [M(LL) ] , which were already resolved into the enantiomers by Alfred Werner, but also in organometallic half-sandwich complexes such as 1 with three- or four-legged piano-stool structure. These complexes have been tools in the elucidation of the spatial course of reactions and in organic syntheses. Applications in enantioselective catalysis are beginning to show up.

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Section: Complexes With Chiral Metal Atoms In Enantioselective Catalysismentioning

confidence: 86%

Optically Active Organometallic Compounds of Transition Elements with Chiral Metal Atoms

Brunner¹

1999

Angew. Chem. Int. Ed.

323

144

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“…For P,N -ligands the QUINAP complex showed a 99% ee at -24 o C for methacrolein and CpH, which also deviated from the norm, by decreasing to 50% ee at -78 o C [76]. The remaining P,N -complex, 23, reacts rapidly, but produces a low ee (46%) [77,78]. The unsymmetrical N,N systems containing oxazolines similar to 24 have produced moderately good ee's, but generally not in the >90% range [22,[79][80][81][82].…”

Section: Diels-alder Reactions With Areneruthenium Complexesmentioning

confidence: 79%

Lewis Acid Catalysis by Ruthenium Complexes

Faller¹,

Parr²

2006

COC

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Recent progress in the Lewis acid catalysis of organic reactions by ruthenium complexes. The review focuses on reactions in which coordinatively unsaturated ruthenium species function as conventional Lewis acids, rather than those involving oxidation or reduction, such as in hydrogenations. Particular emphasis is placed on the development of asymmetric catalysts. INTRODUCTIONLewis acid catalysis continues to be of major utility in organic synthesis [1]. Recent interest in asymmetric catalysis [2,3], particularly for the formation of carbon-carbon bonds, has spurred continuing developments in chiral Lewis acid catalysts [4][5][6]. Classically, Lewis acid catalysts would have involved: main group elements, such as boron or aluminum; tin or zinc; early transition metals, such as titanium; or some lanthanides. Koga developed one of the earliest successful main group catalysts [7]. Yamamoto has been a major contributor to the development of chiral main group Lewis acid catalysts [1,8]. Organometallic Lewis acids of late transition metals have been extensively studied by Beck [9], but the potential for stoichiometric asymmetric reactions on coordinated ligands was largely developed by others, particularly with rhenium [10,11] and molybdenum reagents [12]. These studies of stoichiometric reactions provided valuable information regarding mechanistic aspects and control of nucleophilic attack on coordinated substrates. The lack of sensitivity to decomposition from moisture is a particular advantage of the late transition metal Lewis acids and the potential for straightforward elaboration of the chirality at the metal center via ligand variation has allowed the development of effective asymmetric catalysts based on these metals. Lewis-acid catalysts based on ruthenium have been particularly effective and recent developments on this area will be covered here. Since the mechanisms of a large number of reactions catalyzed by ruthenium complexes involve loss of a ligand to provide a site for coordination of a substrate, a large fraction of the reactions could be viewed as involving Lewis acids. Thus this overview could cover much of the material in a recent monograph [13] which included 383 pages dedicated to ruthenium in organic synthesis. Nevertheless, we will primarily focus on reactions that have been traditionally viewed as catalyzed by Lewis acids and only provide a brief discussion of reactions in which one would expect the oxidation state of the ruthenium to change during the catalytic cycle. Another specific review and more general reviews are also recommended [13][14][15][16].

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“…a,b-Unsaturated aldehydes may r-(g 1 , a) or p-coordinated (g 2 , g 4 , b/c) and were also found to act as bridging ligands (l)g 1 , g 2 , d) (Scheme 2). Complexes (7) and (8) [18]. Furthermore, two type a complexes with aliphatic aldehydes, namely (CO) 5 MnAMn(PhMeC@CHCH 2 CH 2 ACHO-jO)(CO) 4 [19] and [Fe(HCHO-jO) 6 ] [FeI 4 ] 2 AEI 2 [20] have been structrually characterized.…”

Section: Resultsmentioning

confidence: 99%

Ruthenium Catalyzed Reactions of Aldehydes: Molecular Structures of Ruthenium Complexes with Aldehyde Ligands

Sorkau

Wagner

Steinborn

et al. 2005

Transition Met Chem

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RuCl(H)(CO)(PPh 3 ) 3 ](2) was found to catalyze, in the presence of H 2 C=CHSiMe 3 (3), the trimerisation of aldehydes RCHO [R=Et (4a), i-Bu (4b)] yielding 1,3,5-trioxanes (5) and the aldol condensation yielding a,b-unsaturated aldehydes (6). When (4a) was used as a reactant, from these reaction mixtures, the ruthenium complex [RuCl 2 (CO)(PPh 3 ) 2 (EtCH@CMeACHO-jO)] (7) having the aldol condensation product as the ligand crystallized. In the analogous reaction with (4b), the complex [RuCl 2 (CO)(PPh 3 ) 2 (i-BuCHO-jO)] (8) with the aldehyde as ligand was obtained. The constitution of these complexes was established by single-crystal X-ray diffraction measurements. The ruthenium centers are octahedrally coordinated having the aldehyde and the carbonyl ligand in mutually trans positions (coordination index: OC-6-12). The aldehydes are monodentately coordinated via the carbonyl oxygen atom (jO). The coordination induced elongations of the C@O double bonds [1.242(4) Å (7), 1.234(4) Å (8)] indicate an activation of the aldehydes. Furthermore, the RuACO bond lengths [1.842(4) Å (7), 1.823(4) Å (8)] exhibit a relatively low trans influence of the aldehyde ligands. The formation of the complexes (7) and (8) give an indication that the Lewis acidity of the ruthenium center is of importance for aldehyde activation in the catalytic process.

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Chiral ruthenium complexes as catalysts in enantioselective Diels–Alder reactions. Crystal structure of the Lewis acid–dienophile adduct

Cited by 87 publications

References 11 publications

Optically Active Organometallic Compounds of Transition Elements with Chiral Metal Atoms

Optically Active Organometallic Compounds of Transition Elements with Chiral Metal Atoms

Lewis Acid Catalysis by Ruthenium Complexes

Ruthenium Catalyzed Reactions of Aldehydes: Molecular Structures of Ruthenium Complexes with Aldehyde Ligands

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