[2.2]Paracyclophane derivatives in asymmetric catalysis

Gibson, Susan E.; Knight, Jamie D.

doi:10.1039/b300717k

Cited by 281 publications

(111 citation statements)

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“…[2] These structures are usually derived from metallocenes, including ferrocene, [3] or from the [2.2]paracyclophane (Pc) framework. [4] In transition-metal catalysis, [2.2]paracyclophane has been predominantly recognized as a scaffold for phosphane ligands [5] or for N-heterocyclic carbenes.…”

Section: Introductionmentioning

confidence: 99%

Planar‐Chiral Thioureas as Hydrogen‐Bond Catalysts

et al. 2010

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Section: Introductionmentioning

confidence: 99%

Planar‐Chiral Thioureas as Hydrogen‐Bond Catalysts

et al. 2010

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“…Here, even the linear hexanal (4c) showed a reasonable enantiomeric excess with 72 % ee. However, it was not possible to determine the selectivity in the case of undecanal (4b), either by GC on chiral stationary phase, or by 13 C NMR spectroscopy of the (S)-(À)-camphanic acid ester for de determination. Overall, we saw a general trend that the AHPC-based ligands 1 gave better results than ligands 2 derived from BHPC, and in the latter case the (S P ,S)-configurated ligand showed better selectivity than the (R P ,S)-diastereomer.…”

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confidence: 98%

Second‐Generation N,O‐[2.2]Paracyclophane Ketimine Ligands for the Alkenylzinc Addition to Aliphatic and Aromatic Aldehydes: Scope and Limitations

et al. 2006

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Second generation N,O-[2.2]paracyclophane ketimine ligands were investigated for their ability to catalyze the 1,2-addition of alkenylzinc reagents to aliphatic and aromatic aldehydes with special focus on functionalized substrates. For aliphatic aldehydes, which have always been challenging in this field, remarkably high enantiomeric excesses could be determined (50-95 % ee). However, alkenylzinc reagents bearing heteroatoms proved to be demanding substrates for this system. Keywords: alkenylzinc reagents; asymmetric catalysis; chiral allylic alcohols; N,O ligands; paracyclophanes Chiral allylic alcohols are important targets in organic synthesis, especially in natural product synthesis. As intermediates they can be used in further reactions such as allylic substitution, dihydroxylation, ene reaction, cyclopropanation, bromination, or epoxidation. However, the lack of a powerful ligand system impedes the use of the 1,2-addition of alkenylzinc reagents to aldehydes as a key step in natural product synthesis because highly functionalized substrates must be tolerated and high enantiomeric excesses must be achieved.[1] The rare examples in the literature show mostly the use of divinylzinc and substrateinduced diastereoselectivity. [2] In the case of substrate toleration, the catalyzed alkenylzinc addition could be an appropriate method because of the relatively low reactivity of zinc diorganyls towards aldehydes and ketones in comparison to other organometal compounds.[3] However, investigations in this field are few. In contrast, alkyl transfer to aromatic aldehydes is one of the most studied enantioselective catalytic reactions, yet there are only a few examples with high enantiomeric excesses for aliphatic aldehydes.[4] The alkenylzinc transfer is even less investigated; however, interest in this reaction has increased throughout the last years. [5][6][7][8][9][10][11][12] One method elaborated by Oppolzer and Radinov produces mixed alkyl-alkenylzinc species in situ using a transmetalation protocol involving hydroboration of alkynes.[2]paracyclophane-based ligands produce results ranging from good to excellent for this type of reaction, whereas the scope is limited to aromatic aldehydes and fully branched aliphatic aldehydes.[11] Wipf et al. also reported the preparation of alkenylzinc reagents via transmetalation but using zirconium as metal. [9] A comprehensive survey of [2.2]paracyclophanebased ligands can be found in recent reviews.[13] The use of planar-chiral and central-chiral ligands based on paracyclophane systems has emerged en masse since the disclosures by Belokon, Rozenberg et al., [14,15] the Berkessel group, [16] and most notably the Hopf group.[17] Within the last years, various new paracyclophane ligands have been used for asymmetric catalysis. [18][19][20] In particular, the asymmetric 1,2-addition reaction of organozinc compounds such as alkyl-, [21] alkenyl-, [11] and alkynylzinc [22] reagents with aldehydes or imines, [21] respectively, can be efficiently controlled by the use of...

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“…1,2 Perhaps the most famous example is PHANEPHOS, a planar chiral equivalent of BINAP, which, amongst other applications, [3][4][5][6][7] exhibited a higher activity and enantioselectivity than BINAP in the Rh-catalyzed hydrogenation of the tetrahydropyrazine precursor to the HIV protease inhibitor…”

Section: Introductionmentioning

confidence: 99%

Synthesis of Pseudo-geminal-, Pseudo-ortho-, andortho-Phosphinyl-oxazolinyl-[2.2]paracyclophanes for Use as Ligands in Asymmetric Catalysis

Whelligan

Bolm

2006

J. Org. Chem.

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Syntheses of three regioisomers of aromatic-substituted oxazolinyl-phosphinyl-[2.2]paracyclophanes, pseudo-geminal, pseudo-ortho and ortho, have been carried out or, in the latter two cases, newly developed. It has therefore been demonstrated that all aromatic-substituted isomers relevant for use as chelating ligands for asymmetric catalysis are accessible. These P,N-ligands, along with their diastereoisomers, were shown to exhibit widely differing activity and enantioselectivity (up to 89% ee) in the Pd-catalyzed asymmetric allylic alkylation reaction.

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[2.2]Paracyclophane derivatives in asymmetric catalysis

Cited by 281 publications

References 60 publications

Planar‐Chiral Thioureas as Hydrogen‐Bond Catalysts

Planar‐Chiral Thioureas as Hydrogen‐Bond Catalysts

Second‐Generation N,O‐[2.2]Paracyclophane Ketimine Ligands for the Alkenylzinc Addition to Aliphatic and Aromatic Aldehydes: Scope and Limitations

Synthesis of Pseudo-geminal-, Pseudo-ortho-, andortho-Phosphinyl-oxazolinyl-[2.2]paracyclophanes for Use as Ligands in Asymmetric Catalysis

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