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. 2009 Aug 22;65(34):3771-6803.
doi: 10.1016/j.tet.2009.05.079.

Catalytic, asymmetric reactions of ketenes and ketene enolates

Daniel H Paull  1 , Anthony Weatherwax, Thomas Lectka
Affiliations

Catalytic, asymmetric reactions of ketenes and ketene enolates

Daniel H Paull et al. Tetrahedron. .
No abstract available

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Figures

Figure 1.1
Figure 1.1
Electron density map of diphenylketene; red=e− rich, blue=e− deficient.
Scheme 1.1
Scheme 1.1
Shuttle deprotonation.
Figure 1.2
Figure 1.2
Shuttle deprotonation cycle for BQ as the kinetic base.
Figure 1.3
Figure 1.3
The double reaction flask.
Figure 1.4
Figure 1.4
Cinchona alkaloid catalysts.
Figure 1.5
Figure 1.5
Stereochemical models of the putative zwitterionic intermediate of BQ and phenylketene (1d-Nu).
Scheme 2.1
Scheme 2.1
Fu's stereoselective ester synthesis.
Scheme 2.2
Scheme 2.2
Proposed mechanism for catalyzed ester synthesis.
Scheme 2.3
Scheme 2.3
Alternate mechanism for catalyzed ester synthesis.
Scheme 2.4
Scheme 2.4
Synthesis of enol esters.
Scheme 2.5
Scheme 2.5
Screening of pyrrole derivatives.
Scheme 2.6
Scheme 2.6
Catalytic cycle for the aminolysis of disubstituted ketenes.
Scheme 2.7
Scheme 2.7
Reaction of hydrazoic acid with ketenes.
Scheme 3.1
Scheme 3.1
A catalytic, asymmetric synthesis of (S)-malic acid.
Scheme 3.2
Scheme 3.2
Proposed reaction mechanism for a bifunctional system.
Figure 3.1
Figure 3.1
Proposed transition states in Calter's catalytic system.
Figure 3.2
Figure 3.2
Proposed activated complex in Lin's bifunctional cyclization.
Scheme 3.3
Scheme 3.3
The Miyano β-lactone synthesis.
Scheme 3.4
Scheme 3.4
The Kocienski and Pons β-lactone synthesis.
Scheme 3.5
Scheme 3.5
The Romo β-lactone synthesis.
Scheme 3.6
Scheme 3.6
β-Lactone transformations.
Scheme 3.7
Scheme 3.7
Copper(II) catalyzed β-lactone formation.
Scheme 3.8
Scheme 3.8
Proposed mechanism of oxazaborolidine catalyzed β-lactone formation.
Scheme 3.9
Scheme 3.9
Proposed mechanism of NHC catalyzed β-lactone formation.
Scheme 3.10
Scheme 3.10
Ketene dimerization with preformed ketene.
Scheme 3.11
Scheme 3.11
Asymmetric dimerization of a pyrolytically generated ketene.
Scheme 3.12
Scheme 3.12
Synthesis of siphonariene natural products.
Scheme 3.13
Scheme 3.13
NHC-catalyzed dimerization of disubstituted ketenes.
Scheme 3.14
Scheme 3.14
Proposed reaction pathways in the catalyzed formation of ketene dimers.
Scheme 4.1
Scheme 4.1
Staudinger reaction `umpolung'.
Scheme 4.2
Scheme 4.2
β-Lactam synthesis with BQ and proton sponge.
Figure 4.1
Figure 4.1
β-lactams synthesized by asymmetric cycloaddition reaction.
Scheme 4.3
Scheme 4.3
Mechanism of β-lactam formation.
Scheme 4.4
Scheme 4.4
Alternate shuttle deprotonation methods for β-lactam synthesis, BT=thermodynamic base.
Scheme 4.5
Scheme 4.5
Cocatalyst quenching.
Figure 4.2
Figure 4.2
Sample of β-lactams synthesized employing cocatalysts BQ and In(OTf)3.
Figure 4.3
Figure 4.3
Possible roles of the lewis acid.
Scheme 4.6
Scheme 4.6
Metal mediated chemoselectivity of the bifunctional pathway.
Scheme 4.7
Scheme 4.7
PMP- versus OMP-imine reaction rates.
Scheme 4.8
Scheme 4.8
Proposed mechanism of bifunctional [2+2] cycloaddition.
Scheme 4.9
Scheme 4.9
Alternate reaction mechanisms.
Scheme 4.10
Scheme 4.10
Chiral NHC catalyzed formation of β-lactones.
Scheme 4.11
Scheme 4.11
Proposed mechanism of NHC catalyzed reaction.
Figure 4.4
Figure 4.4
N-Heterocyclic carbene catalysts utilized by smith.
Scheme 4.12
Scheme 4.12
Catalytic, asymmetric synthesis of aza-β-lactams.
Scheme 4.13
Scheme 4.13
[2+2] Cycloaddition between ketenes and nitrosoarenes.
Scheme 5.1
Scheme 5.1
Tandem catalytic asymmetric chlorination/esterification.
Scheme 5.2
Scheme 5.2
Ketene phenolysis with proton sponge.
Scheme 5.3
Scheme 5.3
Optimized catalytic, asymmetric bromination/esterification.
Scheme 5.4
Scheme 5.4
The halogenating agent's effect on intermediate lifetime.
Scheme 5.5
Scheme 5.5
Crossover experiments.
Scheme 5.6
Scheme 5.6
The effect of a hindered brominating reagent.
Scheme 5.7
Scheme 5.7
Selection of the chlorinating agent.
Scheme 5.8
Scheme 5.8
Possible catalytic cycles for the α-chlorination of disubstituted ketenes.
Scheme 5.9
Scheme 5.9
Transformations of enol ester products.
Scheme 5.10
Scheme 5.10
Fluorination of dually activated ketenes.
Figure 5.1
Figure 5.1
Selected fluorinated products.
Scheme 6.1
Scheme 6.1
o-Benzoquinone derivatives in [4+2] cycloadditions with ketene enolate.
Scheme 6.2
Scheme 6.2
Preliminary o-quinone reactions.
Figure 6.1
Figure 6.1
A selection of o-chloranil-derived cycloadducts.
Scheme 6.3
Scheme 6.3
Derivatization of benzodioxinone cycloadducts.
Figure 6.2
Figure 6.2
A selection of α-hydroxy esters, from o-chloranil and acid chlorides.
Figure 6.3
Figure 6.3
The Lewis acid in bifunctional catalytic systems.
Figure 6.4
Figure 6.4
DFT (B3LYP/LANL2DZ) calculations of putative o-chloranil (87a) bound metal complexes.
Scheme 6.4
Scheme 6.4
Palladium(II) cocatalyzed cycloaddition reaction mechanism.
Scheme 6.5
Scheme 6.5
Synthesis of α-hydroxy γ-lactones and lactams.
Scheme 6.6
Scheme 6.6
Products obtained from reactions of quinone imides.
Figure 6.5
Figure 6.5
Benzoxazinone products.
Figure 6.6
Figure 6.6
A selection of N-aryl α-amino acid derivatives.
Figure 6.7
Figure 6.7
Highly biologically significant α-amino acid derivatives.
Figure 6.8
Figure 6.8
A selection of N-protected α-amino acid derivatives.
Scheme 6.7
Scheme 6.7
The bifunctional system to form α-amino acid derivatives.
Figure 6.9
Figure 6.9
Examples of improved yield for the bifunctional system.
Scheme 6.8
Scheme 6.8
A bifunctional catalytic system to produce quinoxalinones.
Figure 6.10
Figure 6.10
A sample of quinoxalinone products.
Scheme 6.9
Scheme 6.9
Proposed mechanism of regioselective cycloaddition.
Scheme 6.10
Scheme 6.10
Drug target syntheses, R=CO2-i-Pr.
Scheme 6.11
Scheme 6.11
Nelson's bifunctional [4+2] cycloaddition reaction.
Scheme 6.12
Scheme 6.12
Evans's CuII catalyzed [4+2] cycloaddition reaction.
Scheme 6.13
Scheme 6.13
NHC catalyzed δ-lactone synthesis.
Scheme 6.14
Scheme 6.14
Activated aldehyde cycloaddition.
Scheme 6.15
Scheme 6.15
Amino alchohol catalyzed reaction.
Scheme 6.16
Scheme 6.16
Proposed mechanism of δ-lactone formation.
Scheme 6.17
Scheme 6.17
Simple δ-lactone derivatization.
Scheme 7.1
Scheme 7.1
Synthesis of chiral allenes.
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