4th EucheMs chemistry congress

Poster Session 2
s1361
chem. Listy 106, s257–s1425 (2012)
Poster session 2 - organic chemistry
P - 0 9 9 8
SyntheSiS of triCyCLiC indoLe derivAtiveS
viA ASyMMetriC orGAnoCAtALySiS
S. vArGA 1 , K. ArAdi 1 , C. SzAntAy 1 , t. SooS 1
1 Research Centre for Natural Sciences Hungarian Academy of
Sciences, Institute of Organic Chemistry, Budapest, Hungary
Asymmetric organocatalysis is a powerful method to
assemble chiral molecules without using transition metals or harsh
reaction conditions. Most of the applied organocatalysts have been
synthesized from renewable sources (e.g., amino acids, alkaloids)
and used in enantio- and diastereoselective syntheses of complex
chiral molecules, which are valuable building blocks.
We have developed bifunctional cinchona based thiourea
catalysts, which have been used in several asymmetric
transformations with high enantioselectivities and yields [1, 2] .
Recently, we have applied these bifunctional catalysts in an
iterative Michael-Michael-Henry process to diastereoselectively
construct chiral cyclohexanes. This unique selectivity and
reactivity were explained with the double diastereocontrol
phenomenon [3] .
As part of our synthetic program, we wished to apply our
catalysts in the synthesis of biologically active, natural products,
namely, indole alkaloids. Thus, we selected 3,4-substituted indole
compounds to transform them via efficient enantioselective
organotandem procedures to ergot and secergoline type alkaloids.
Our results in the asymmetric synthesis of various indole
derivatives will be disclosed in the poster.
Acknowledgement: Financial support provided by grants
OTKA 75705, K-69086, NK-77784 are gratefully
acknowledged.
references:
1. B. Vakulya, Sz. Varga, A. Csámpai, T. Soós Org. Lett.
2005, 7, 1967-1969.
2. B. Vakulya, Sz. Varga, T. Soós J. Org. Chem. 2008, 73,
3475-3480.
3. Sz. Varga, G. Jakab, L. Drahos, T. Holczbauer,
M. Czugler, T. Soós Org.Lett. 2011, 13, 5416-5419.
Keywords: Organocatalysis; Alkaloids; Enantioselectivity;
4 th EucheMs chemistry congress
P - 0 9 9 9
dehydroGenAtive heCK reACtion of furAnS
And thioPheneS with StyreneS under MiLd
ConditionS
A. vASSeur 1 , J. MuzArt 1 , J. Le BrAS 1
1 Institut de Chimie Moléculaire de Reims, Méthodologie en
Synthese Organique, Reims, France
The Pd-catalyzed direct cross-couplings of arenes with
alkenes through C-H activation, also called intermolecular
Dehydrogenative Heck Reactions (DHRs), have drawn much
attention in recent years. [1]
Among the arenes used in DHRs, furans and thiophenes
have received little attention because the former are acid sensitive
and the latter require elevated temperatures, due to their higher
aromatic resonance energy and stability. Moreover, styrenes are
electron-rich compounds and are a notoriously difficult substrate
class due to facile polymerization and cleavage under palladium
oxidative conditions.
In 2008, we have reported the synthesis of difurylalkanes
through the bis-coupling of 2-alkylfurans with various alkenes,
including styrenes. [2] Then, we reported a dehydrogenative
coupling of furans and styrenes leading to Heck-type products
which allowed the use of chlorinated and fluorinated substrates. [3]
The previous transformation occured under mild conditions
but nevertheless, brominated substrates were reluctant to react.
Glorius et al. have recently shown that brominated compounds
can be formed with no proto-debromination using Rh catalysts;
however few examples have been reported and the scope of
substrates remains to be developed. [4] We will present the DHRs,
under mild conditions, of furans and thiophenes with styrenes,
including brominated substrates. [5] The influence and the role of
the oxidizing agent on the activity of the catalyst will be also
discussed.
references:
1. Le Bras, J.; Muzart J. Chem. Rev. 2011, 111, 1170-1214.
2. Thiery, E.; Harakat, D.; Le Bras, J.; Muzart, J.
Organometallics 2008, 27, 3996-4004.
3. Aouf, C.; Thiery, E.; Le Bras, J.; Muzart, J. Org Lett.
2009, 11, 4096-4099.
4. a) Rakshit, S.; Grohmann, C.; Besset, T.; Glorius, F.
J. Am. Chem. Soc. 2011, 133, 2350-2353;
b) Patureau, F. W.; Glorius, F. J. Am. Chem. Soc. 2010,
132, 9982-9983.
5. Vasseur, A.; Muzart J.; Le Bras, J. Chem. –Eur. J. 2011,
17, 12556-12560.
Keywords: C-H activation; Cross-coupling; Heck reaction;
Palladium; Homogeneous catalysis;
AUGUst 26–30, 2012, PrAGUE, cZEcH rEPUbLIc