Planar and Central Chiral [2.2]Paracyclophanes as Powerful Catalysts for Asymmetric 1,2-Addition Reactions

Bräse, Stefan; Dahmen, Stefan; Höfener, Sebastian; Lauterwasser, Frank; Kreis, Michael; Ziegert, Robert E.

doi:10.1055/s-2004-836029

Cited by 92 publications

(32 citation statements)

References 18 publications

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“…[5][6][7]4 Other drawbacks to the KR include the need to separate the desired allylic alcohol from the epoxy alcohol product and a maximum yield of 50%. 20 More efficient methods to prepare allylic alcohols include asymmetric vinylation of aldehydes [21][22][23][24][25]13,15,[8][9][10][26][27][28] or ketones 29,30 (Scheme 2) and reductive coupling of alkynes and carbonyl compounds. 31-36 These methods simultaneously generate the C-C bond and a stereogenic center in a single step.…”

Section: Introductionmentioning

confidence: 99%

Catalytic Asymmetric Generation of (Z)-Disubstituted Allylic Alcohols

et al. 2007

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A one-pot method for the direct preparation of enantioenriched (Z)-disubstituted allylic alcohols is introduced. Hydroboration of 1-halo-1-alkynes with dicyclohexylborane, reaction with t-BuLi, and transmetallation with dialkylzinc reagents generates (Z)-disubstituted vinylzinc intermediates. In situ reaction of these reagents with aldehydes in the presence of a catalyst derived from (−)-MIB generates (Z)-disubstituted allylic alcohols. It was found that the resulting allylic alcohols were racemic, most likely due to a rapid addition reaction promoted by LiX (X = Br and Cl). To suppress the LiX promoted reaction, a series of inhibitors was screened. It was found that 20-30 mol % tetraethylethylene diamine (TEEDA) inhibited LiCl without inhibiting the chiral zinc-based Lewis acid. In this fashion, (Z)-disubstituted allylic alcohols were obtained with up to 98% ee. The asymmetric (Z)-vinylation could be coupled with tandem diastereoselective epoxidation reactions to provide epoxy alcohols and allylic epoxy alcohols with up to three contiguous stereogenic centers, enabling the rapid construction of complex building blocks with high levels of enantio-and diastereoselectivity.

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Section: Introductionmentioning

confidence: 99%

Catalytic Asymmetric Generation of (Z)-Disubstituted Allylic Alcohols

et al. 2007

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“…This enantioselective C-C bond formation for the preparation of optically active secondary alcohols has been intensely studied with various catalytic systems. [27][28][29] The salts were first tested in the addition of diethylzinc to benzaldehyde (16), as shown in Scheme 2, the reactions being performed at room temperature and dif-ferent solvents being tested. The results are summarized in Table 3.…”

Section: Resultsmentioning

confidence: 99%

Easily Accessible Chiral Imidazolinium Salts Bearing Two Hydroxy‐Containing Substituents as Shift Reagents and Carbene Precursors

2006

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The behavior of new enantiopure imidazolinium salts bearing two hydroxy‐containing substituents as chiral shift reagents and as carbene precursors for diethylzinc addition to aldehydes is presented. The new hydroxy‐containing imidazolinium salts can be prepared in a few steps from amino alcohols and qualify as new tridentate ligands and ionic liquids.(© Wiley‐VCH Verlag GmbH & Co. KGaA, 69451 Weinheim, Germany, 2006)

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“…[11][12][13][14] In particular, hydroxy[2.2]paracyclophane ketimine ligands can efficiently control the asymmetric 1,2-addition reaction of zinc reagents [15] such as alkyl-, [8,16,17] alkenyl-, [18] aryl, [19] and alkynylzinc [20] reagents to aldehydes or imines. [14,16,19] The well-known ortho-acylated hydroxy[2.2]paracyclophanes 2 (R 1 = methyl, AHPC) and 3 (R 1 = phenyl, BHPC) are key intermediates for these ligands. [6,21] They can also be condensed with primary amines to give ketimines 11 a and 12 a.…”

Section: Introductionmentioning

confidence: 99%

Structurally Diverse Second‐Generation [2.2]Paracyclophane Ketimines with Planar and Central Chirality: Syntheses, Structural Determination, and Evaluation for Asymmetric Catalysis

Lauterwasser

Nieger

Mansikkamäki

et al. 2005

Chemistry A European J

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A set of 20 novel [2.2]paracyclophane ketimines with planar and central chirality has been synthesized from enantiomerically pure and racemic 5-acyl-4-hydroxy[2.2]paracyclophane and alpha-branched chiral amines. Their X-ray structures were determined to elucidate the three-dimensional structures and the absolute configuration. The ketimines were used as catalysts in the asymmetric 1,2-addition reactions of diethylzinc with substituted benzaldehydes to furnish chiral alcohols in up to 95 % ee.

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Planar and Central Chiral [2.2]Paracyclophanes as Powerful Catalysts for Asymmetric 1,2-Addition Reactions

Cited by 92 publications

References 18 publications

Catalytic Asymmetric Generation of (Z)-Disubstituted Allylic Alcohols

Catalytic Asymmetric Generation of (Z)-Disubstituted Allylic Alcohols

Easily Accessible Chiral Imidazolinium Salts Bearing Two Hydroxy‐Containing Substituents as Shift Reagents and Carbene Precursors

Structurally Diverse Second‐Generation [2.2]Paracyclophane Ketimines with Planar and Central Chirality: Syntheses, Structural Determination, and Evaluation for Asymmetric Catalysis

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