Transcript Diapositive 1

Rhodium-Catalyzed Chemo- and Regioselective Decarboxylative Addition of βKetoacids 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
•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
Prof. Bernhard Breit
His research interests include the developement and exploration of
new concepts and methods for organic synthesis and homogeneous
catalyst.
Background
Under certain conditions, transition metals produce branched allylic compounds (right)
Trost M.B. ; Fullerton J. T. J. Am. Chem. Soc.1973, 95, 292–294
Liu, W.-B.; Reeves, C. M.; Virgil, S. C.; Stoltz, B. M. J. Am. Chem. Soc. 2013, 135, 10626.
Background
Koscher, P.; Lumbroso, A.; Breit, B. J. Am. Chem. Soc. 2011, 133, 20746.
Allenes
Van' Hoff, J.H.; La chimie dans L'espace, 1885, Bazendijk, Rotterdam
Burton, B.S.; Pechmann, H.v., Ber, Dtsh, Chem, Ges, 1887, 20, 145-149
http://wps.prenhall.com/wps/media/objects/602/616516/Chapter_07.html
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
Min, S.-J.; Jung, M.E., J. Am. Chem. Soc., 2005, 127, 10834-10835
Brummond, K.M.; Kerekes, A.D.; Wan, H., J. Org. Chem., 2002, 67, 5156-5163
Pd-catalyzed tandem coupling isomerization reaction (CIR)
Shen R.; Chen K.; Deng Q.; Yang J.; Zhang L. Org. Lett. ASAP
Allenes in natural products
As of 2004, around 150 natural products containing allenes were identified
Hoffmann-Röder, A.; Krause, N.; Angew. Chem. Int. Ed.; 2004, 43, 1196-1216
Synthesis of allene.
•Crabbé Homologation and modification.
•Nucleophilic attack on alkyne
•[2,3] sigmatropic rearrangement
Li Z.; Boyarskikh V.; Hansen H. J.; Autschbach J.; Museav G.D.; Davies L. M. H. J.Am.Chem.Soc. 2012, 134, 15497−1550
Background
Koscher, P.; Lumbroso, A.; Breit, B. J. Am. Chem. Soc. 2011, 133, 20746.
This paper
•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.
Optimization of reaction conditions
Scope of regioselective synthesis of tertiary carbon centers
Scope of regioselective synthesis of quaternary carbon centers
Diallylation of acetone-1,3-dicarboxylic acid
Mechanistic studies
2 questions regarding this mechanism :
•Decarboxylation or allylation goes first ?
•Inner-sphere or outer-sphere mechanism ?
Proposed mechanism
Conclusions
•They have developed a highly regioselective decarboxylative addition of β-ketoacids to allenes
to 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.