rhodium-catalyzed chemo- and regioselective decarboxylative addition of β -
DESCRIPTION
Rhodium-Catalyzed Chemo- and Regioselective Decarboxylative Addition of β - Ketoacids to Allenes: Efficient Construction of Tertiary and Quaternary Carbons Centers. Literature meeting February 19 th 2014. By : Antoine Caron. Li C.; Breit B. J.Am.Chem.Soc . 2014 , 136, 862−865. - PowerPoint PPT PresentationTRANSCRIPT
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Rhodium-Catalyzed Chemo- and Regioselective Decarboxylative Addition of β-Ketoacids to Allenes: Efficient Construction of Tertiary and Quaternary Carbons Centers
By : Antoine Caron
Literature meeting February 19 th 2014
Li C.; Breit B. J.Am.Chem.Soc. 2014, 136, 862−865
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Prof. Bernhard Breit
•Ph.D. at University of Kaiserslautern in 1993•Post-doctoral studies with Trost at Standford•1999-2001 professor of organic chemistry at University of Heidelberg•Since 2001, holds a chair of organic chemistry at the University of Freiburg
His research interests include the developement and exploration of new concepts and methods for organic synthesis and homogeneous catalyst.
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Background
Under certain conditions, transition metals produce branched allylic compounds (right)
Liu, W.-B.; Reeves, C. M.; Virgil, S. C.; Stoltz, B. M. J. Am. Chem. Soc. 2013, 135, 10626.Trost M.B. ; Fullerton J. T. J. Am. Chem. Soc.1973, 95, 292–294
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Background
Koscher, P.; Lumbroso, A.; Breit, B. J. Am. Chem. Soc. 2011, 133, 20746.
+HO R
O [Rh(COD)Cl2(R-R)-DIOP
Cs2CO3 DCE
O
R
O
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Allenes
R3
R4R2
R1R2R1
R3
R4
OHH
H
CH3
H
CH3HO
H
12
3
4H
CH3
HHO
1
2
3 4
S configuration S configuration
12
3
Van' Hoff, J.H.; La chimie dans L'espace, 1885, Bazendijk, RotterdamBurton, B.S.; Pechmann, H.v., Ber, Dtsh, Chem, Ges, 1887, 20, 145-149http://wps.prenhall.com/wps/media/objects/602/616516/Chapter_07.html
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Allenes in organic synthesis
Allenes are used in many ways in organic synthesis. These methods are often applied toward making a natural product. They are used as substrates in many well known transformations:
•Diels-Alder reaction
•Pausan-Khand cyclization
O
O
H
Me
Me2AlCl-78°C to -20°C
80%O
Me HO
Min, S.-J.; Jung, M.E., J. Am. Chem. Soc., 2005, 127, 10834-10835
DMPS
H Mo(CO)6DMSO/Toluene
95°C80% E:Z 8:1 O
HDMPS
H
95% ee
R
H
R
H
MLx
MLx
O
HR
H
O
HR
H
Brummond, K.M.; Kerekes, A.D.; Wan, H., J. Org. Chem., 2002, 67, 5156-5163
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Shen R.; Chen K.; Deng Q.; Yang J.; Zhang L. Org. Lett. ASAP
Pd-catalyzed tandem coupling isomerization reaction (CIR)
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Allenes in natural products
OOH
O
AcOOH
AcOOH OH
O
OO
Fucoxanthin
Peridinin
Carotinoids
CO2HMycomycin
Hoffmann-Röder, A.; Krause, N.; Angew. Chem. Int. Ed.; 2004, 43, 1196-1216
As of 2004, around 150 natural products containing allenes were identified
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Synthesis of allene.
•Crabbé Homologation and modification.
•Nucleophilic attack on alkyne
•[2,3] sigmatropic rearrangement
R+ R'CHO
Cu R''2NH R
R'
R'''
LG
R'R'' Nu
R'''
R'
R''
Nu
R'''
OH
R'R''
EDG CO2Me
N2
Rh(II)
R'''
O+
R'R''
H
Rh-EDGMeO2C
R'''
R'
R''
EDG CO2Me
HO
Li Z.; Boyarskikh V.; Hansen H. J.; Autschbach J.; Museav G.D.; Davies L. M. H. J.Am.Chem.Soc. 2012, 134, 15497−1550
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Background
S
O
CoA
-O S
O O
CoA
S
O
ACP
-O S
O O
ACP
S
O O
ACP
Acetyl CoA:ACP transacylase
Malonyl CoA:ACP transacylase
3-ketoacyl-ACP synthetase
SH-ACP + CO2
Various fatty acids
R'HO
O
R''R'
O R''
O
[Rh]
R'R''
O
R'
R''
O
[Rh] R'''R''' X
Koscher, P.; Lumbroso, A.; Breit, B. J. Am. Chem. Soc. 2011, 133, 20746.
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This paper
R'
R'' +HO R'''
O O x mol% [Rh(cod)Cl]2y mol% ligand
DCE, rt,
O
R'''
R'R''
•The carboxylic acid may initiate the reaction through the formaton of the allyl-Rh intermediate.
•The nucleophilicity of the α carbon would be enhanced.
•CO2 can be eliminated as a traceless directing group.
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Optimization of reaction conditions
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Scope of regioselective synthesis of tertiary carbon centers
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Scope of regioselective synthesis of quaternary carbon centers
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Diallylation of acetone-1,3-dicarboxylic acid
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Mechanistic studies
2 questions regarding this mechanism :
•Decarboxylation or allylation goes first ?
•Inner-sphere or outer-sphere mechanism ?
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Proposed mechanism
O
O O
R
R'
11 =
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Conclusions
•They have developed a highly regioselective decarboxylative addition of β-ketoacids to allenesto give γ-δ-unsaturated ketones.
•Quaternary and tertiary carbons centers could be generated in high yield.
•A mild and atom economic method was developed.
•Milder conditions than the enolate allylation under basic conditions.