4th EucheMs chemistry congress

Poster Session 2
s1273
chem. Listy 106, s257–s1425 (2012)
Poster session 2 - organic chemistry
P - 0 8 2 0
ChirAL iMidAte-PhoSPhAneS: ProGreSS in
their SyntheSiS And APPLiCAtion AS
n,P-LiGAndS
K. Bert 1 , t. noeL 2 , P. JAnSSenS 1 ,
J. vAn der eyCKen 1
1 Ghent University, Organic Chemistry, Gent, Belgium
2 Eindhoven University of technology, Chemical Engineering
and Chemistry, Eindhoven, Netherlands
Chiral imidate-phosphanes were recently developed in our
lab as a new type of P,N-ligands, easily accessible via a one-step
procedure starting from an imidate precursor and a commercially
available chiral aminophosphane. [1]
We wish to report here on the performance of these ligands
in the Pd(0)-catalyzed allylic alkylation and amination and the
Ir(I)-catalyzed asymmetric hydrogenation of unfunctionalized
olefins. [2]
The observed performance of our imidate-phosphane
ligands with various carbon and amine nucleophiles in the
Pd(0)-catalyzed allylic alkylation and amination appeared to be
good to excellent (yields up to 99% and ee’s up to 99%). Moderate
to very good results (yields up to 99.9% and ee’s up to >99%)
were obtained with our imidate-phosphane ligands in the
Ir(I)-catalyzed asymmetric hydrogenation of unfunctionalized
olefins.
references:
1. Noel, T.; Bert, K.; Van der Eycken, E.; Van der Eycken, J.
Eur. J. Org. Chem. (2010), 21, 4056-4061.
2. Noel, T., Bert, K., Janssens, P. and Van der Eycken, J.
(2012) Chiral Imidate Ligands: Synthesis and Applications
in Asymmetric Catalysis, in Innovative Catalysis in
Organic Synthesis: Oxidation, Hydrogenation, and C-X
Bond Forming Reactions (ed P. G. Andersson),
Wiley-VCH Verlag GmbH & Co. KGaA, Weinheim,
Germany. doi: 10.1002/9783527646586.ch14
Keywords: Asymmetric catalysis; Asymmetric synthesis;
Hydrogenation; Palladium;
4 th EucheMs chemistry congress
P - 0 8 2 1
AroMAtiC CArBoxyLiC ACidS in
deCArBoxyLAtive etherifiCAtion
S. BhAdrA 1 , w. i. dziK 1 , L. J. GoSSen 1
1 Technische Universität Kaiserslautern, FB Chemie –
Organische Chemie, Kaiserslautern, Germany
Transition metal-catalyzed decarboxylative coupling
reactions have emerged as a powerful strategy to form carbon–
carbon or carbon–heteroatom bonds starting from carboxylic
acids. In these reactions, C–C bonds to carboxylate groups are
cleaved, and in their place, new carbon–carbon bonds are formed.
Decarboxylative cross-couplings constitute advantageous
alternatives to traditional cross-coupling or addition reactions
involving preformed organometallic reagents. While the
overwhelming majority of decarboxylative couplings of aromatic
carboxylates proceed with formation of C–C bonds, the only
example of C–heteroatom bond forming reactions are restricted
to C–S and C–Se bond formation.
Here we present the decarboxylative C–O coupling as a
practical access to alkyl-aryl and diaryl ethers avoiding the use of
the often expensive organic halide and boronic acid precursors.
Alkyl aryl- or diaryl ethers are synthesized starting from easily
available aromatic carboxylic acids and alkoxysilanes or aryl
boranes respectively. The reaction occurs under aerobic conditions
in the presence of silver carbonate as the decarboxylation catalyst
and copper acetate as the cross-coupling catalyst. Thus, aromatic
carboxylates with various electron-withdrawing and –donating
groups in the ortho position e.g. nitro, methoxy, dimethylamino,
sulfonyl, chloro, fluoro, trifluoromethyl or phenyl groups, were
successfully converted to the corresponding aryl ether. On the
other hand, for carboxylates with a low tendency to extrude
carbon dioxide, an alternative pathway consisting of ortho
functionalization followed by protodecarboxylation has been
shown to be functional, so that the ether group is installed in the
ortho rather than theipso position of the former carboxylate group.
This approach combines the key benefit of regiospecificity with
the broad availability, low cost, and easy handling of carboxylate
substrates and therefore serves as an attractive alternative to the
traditional Buchwald-Hartwig and Chan-Evans-Lam reactions.
Keywords: C-C activation; cross-coupling; regioselectivity;
copper; silver;
AUGUst 26–30, 2012, PrAGUE, cZEcH rEPUbLIc