Contact Data

Prof. Dr. Laschat
Universität Stuttgart
Pfaffenwaldring 55
D-70569 Stuttgart

Sec. 
Ursula Henn
NWZ I, 5-102
+49711 685 64268
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Research

reseach

Here, we present our research topics.

The asymmetric rhodium catalyzed 1,4-addition of arylboronic acids to α,β-unsaturated carbonyl compounds also known as Hayashi Miyaura reaction is an important reaction for the asymmetric carbon-carbon bond formation. The reaction was first mentioned in 1997 and 1998 by Hayashi and Miyaura.[1,2] Through the preliminary studies of Hayashi, Carreira[3] and Grützmacher[4], chiral diene ligands came forward as a new class of ligands in Rh- and Ir-catalysed reactions.
We were able to synthesize different tropane-derived phosphorus–olefin hybrid ligands 1 and disubstituted chiral diene ligands with pentalene as backbone 2 and could show successfully their application in the 1,4-addition of arylbronic acids to enones.[5,6] Therefore we are currently interested in the development of new chiral diene and phosphorous/olefin ligands and their area of applications.

catalysis

[1] M. Sakai, H. Hayashi, N. Miyaura, Organometallics 1997, 16, 4229–4231.
[2] Y. Takaya, M. Ogasawara, T. Hayashi, M. Sakai, N. Miyaura, J. Am. Chem. Soc. 1998, 120, 5579–5580.
[3] J.-F. Paquin, C. R. J. Stephenson, C. Defieber, E. M. Carreira, Org. Lett. 2005, 7, 3821–3824.
[4] F. Läng, F. Breher, D. Stein, H.Grützmacher, Organometallics 2005, 24, 2997–3007.
[5] S. Vlahovic, N. Schädel, S. Tussetschläger, and S. Laschat, Eur. J. Org. Chem. 2013, 1580–1590.
[6] S. Helbig, S. Sauer, N. Cramer, S. Laschat, A. Baro, W. Frey, Adv. Synth. Catal. 2007, 349, 2331 – 2337.
Merocyanine compounds belong to the class of “push–pull” dyes and show multifunctional characteristics. Thus, their scope for application is ever increasing and they can be found in such widespread fields as data storage and UV-absorbing materials for food packaging.[1] However, inherent limitations regarding long-term stability, efficiency, and processability require detailed studies on structure–property relationships.[2] We carry out a systematic experimental and theoretical investigation of the absorption and emission spectra of dyes that vary in either chromophore length or acceptor unit. The consequent results provide information on structure-property relationships, which could be used to tailor potentially functional dyes.[3]

research_kress

[1] S. Saito, A. Osuka, Angew. Chem. Int. Ed. 2011, 50, 4342–4373.
[2] Z. Chen, A. Lohr, C. R. Saha-Möller, F. Würthner, Chem. Soc. Rev. 2009, 38, 564.
[3] K. C. Kreß, T. Fischer, J. Stumpe, W. Frey, M. Raith, O. Beiraghi, S. H. Eichhorn, S. Tussetschläger, S. Laschat, ChemPlusChem 2014, 79, 223–232.

Discotic Liquid Crystals


The discovery of stable liquid crystalline phases formed by disk-shaped molecules with long alkyl chains in their periphery is generally dated to the seminal work of Chandrasekar published in 1977.[1] Since then discotic liquid crystals have attracted the attention of many research groups worldwide. Due to the one dimensional charge and ion transport in the columnar mesophase, the ability of liquid crystals (LCs) to self-heal structural defects by thermal annealing and the ease of processing via spin coating, drop casting and other solution processing methods highly useful applications[2–4] could be realized such as organic solar cells,[5] organic field effect transistors[6] and organic light emitting diodes.[7] For the application possibilities the electronic structure of discotics is of great importance.

Boroxines

Introducing heteroatoms to the core unit can be used to tune the electronic features of the liquid crystals. Boroxines as a core unit for discotic compounds provide a quick access to tripodal molecular architecture. These boroxines are the condensation product of three boronic acids and therefore consist of a 6-membered (-B-O-)3 ring system. The published synthesis towards these mesogens provides the first target-oriented approach to liquid crystalline boroxines. With simple threefold alkylated benzene side-groups they display broad, highly ordered Colh mesophases.[8]

Boroxin

Crown Ethers

Another possibility in creating molecular electronics give the crown-ether based liquid crystals. These consist of three main parts the central crown-ether, varying number of triphenylenes and the peripheral side chains.[9] Previous work showed the application potential, e.g. photo conductivity or carrier mobility.[10] These properties can be tuned by varying the components of the molecular construction kit. Through changes of the molecular structure important features like the geometry of the mesophase[11] or the mesophase range towards room temperature can be altered.

Crown

References

[1] Chandrasekhar, S.; Sadashiva, B.K.; Suresh, K.A. Pramana, 1977, 9, 471–480.
[2] Sergeyev, S.; Pisula, W.; Geerts, Y.H. Chem. Soc. Rev. 2007, 36, 1902–1929.
[3] Woltman, S.J.; Jay, G.D.; Crawford, G.P. Nat. Mater. 2007, 6, 929–938.
[4] Kaafarani, B.R. Chem. Mater. 2011, 23, 378–396.
[5] Kumar, S. Curr. Sci. 2002, 82, 256–257.
[6] Bushby, R.J.; Kawata, K. Liq. Cryst. 2011, 38, 1415–1426.
[7] Kopitzke, J.; Wendorff, J.H. Chemie Unserer Zeit 2000, 34, 4–16.
[8] Wöhrle, T.; Baro, A.; Laschat, S. Materials 2014, 7, 4045–4056.
[9] Kaller, M.; Tussetschläger, S.; Fischer, P.; Deck, C.; Baro, A.; Giesselmann, F.; Laschat, S.; Chem. Eur. J. 2009, 15, 9530–9542.
[10] Staffeld, P.; Kaller, M.; Beardsworth, S. J.; Tremel, K.; Ludwigs, S.; Laschat, S.; Giesselmann, F.: J. Mater. Chem. C 2013, 1, 892–901.
[11] Wöhrle, T.; Kirres, J.; Kaller, M.; Mansueto, M.; Tussetschlager, S.; Lascha, S.; J. Org. Chem. 2014, 79, 10143−10152.



Calamitic Ionic Liquid Crystals


Ionic liquid crystals are now an established field of research in organic synthesis as they combine the advantages of ionic liquids (ILs) and liquid crystals (LCs) creating a class of substances with very promising industrial applications for example in displays. Calamitic liquid crystals were the first type of LCs investigated. For some time the calamitic shape was considered necessary for liquid crystalline behaviour.[1] While many other shapes of liquid crystals are known for ionic liquid crystals (ILCs) calamitic shapes offer great potential due to the formation of bilayer structures formed by a charged LC and it’s counter ion, which offer one-dimensional ion conductivity.[2] The ILCs we focus on typically consist of a central mesogenic unit that has a flexible alkyl chain on one end and the ionic head group attached either directly or via an alkyl chain on the other.[3,4]
Calamitic 1

Guanidinium Ion Pairs

Guanidine, with its ability to form stable cations has been used in ionic liquids for quite some time now. To create a class of ILCs with low melting points we try to create ion pairs where both the cation and anion contain a mesogenic group such as p alkoxybiphenyl or p-alkoxybenzene with a charged head group. Guanidine suits our purpose very well with its stability, while sulfonates give non-nucleophilic anions.[3,5]
Calamitic 3

Phenylpyrimidines

The phenylpyrimidine structure has created considerable interest over time as a mesogen as it allows to compare a flat core (2-phenylpyrimidine 1) versus a twisted one (5-phenyl-pyrimidine 2).[4]
Calamitic 2

References

[1] D. Vorländer, Z. Phys. Chem., Stoechiom. Verwandtschaftsl. 1923, 105, 211-254.
[2] T. Kato, Science, 2002, 295, 2414-2418.
[3] M. Butschies, W. Frey, S. Laschat, Chem. Eur. J. 2012, 18, 3014-3022.
[4] G. F. Starkulla, S. Klenk, M. Butschies, S. Tussetschläger, S. Laschat, J. Mater. Chem. 2012, 22, 21987-21997.
[5] M. Butschies, M. M. Neidhardt, M. Mansueto, S. Laschat, S. Tussetschläger, Beilstein J. Org. Chem. 2013, 9, 1093-1101.

Natural Products


Gephyronic Acid

Gephyronic acid is, due to its biological activity and structural similarity with tedanolid and myriaporon, an interesting target compound. It can be retrosynthetically separated into the western and eastern fragment. As these synthetic routes provide both fragments in only moderate yields, therein lies a great potential for a synthetic improvement to the important target compound. It is our goal to realize the synthesis of both fragments in the simplest, cleanest and most cost-effective routes possible, during which derivatives could also be achieved, in order to fully investigate wherein such compounds, the maximum biological activity can be found.

research_hassnik



Borrelidine Analogues

The macrolide antibiotic borrelidine is an interesting target compound for several research groups due to its unique structure and its versatile biological activity.[1,2] The natural product was first isolated from Streptomyces rochei in 1949 by Berger et al. as an antibiotic possessing anti-borrelia activity.
Its biological activity includes, but is not limited to, the selective inhibition of threonyl tRNA synthetase, antiviral as well as antiangiogenesis activities. In order to gain a better understanding of the researching for viable synthetic routes to borrelidine and its analogues and testing them in several cell lines.
Borrelidine

References

[1] Nagamitsu T., Harigaya Y. Omura S., Proc. Japan Acad Ser. B 2005, 81, 244-256.
[2] Theurer M., El Bay Y., Koschorreck K., Urlacher Vlada B., Rauhut G., Baro A., and Laschat S. Eur. J. Org. Chem. 2011, 4241-4249.



Molecular Bionics


Elastin is an important extracellular matrix protein in connective tissue. The unique properties of the skin, such as high elasticity and tensile strength can be attributed to elastin. It is constructed of flexible and water-soluble tropoelastin polymer chains which are connected mainly by the cross-linker desmosine.[1] Inspired by this structure we design new cross-linkers based on pyridinium salts with acrylate or acrylamide as connecting unit.[2] These units can react with thiolated hyaluronic acid by the thio-Michael addition and form a hydrogel.[3]
MolecularBionics

References

[1] M. Akagawa, K. Suyama, Connective Tissue Research 2000, 41, 131.
[2] M. Mateescu et al., Synthesis 2014, 46, 1243-1253.
[3] V. Hagel et al., Nature Sci. Rep. 2013, 3, 2043 (1-5).