Discotic liquid crystals synthesis

Kumar S, Pal SK (2005) Ionic discotic liquid crystals synthesis and characterization of pyridinium bromides containing a triphenylene core. Tetrahedron Lett 46 4127-4130... 

Discotic liquid crystals (particularly, heterocyclic compounds) and their applications from tailor-made synthesis to plastic electronics 07AG(E) 4832. 

S. Laschat, A. Baro, N. Steinke, F. Giesselmaim, C. Hagele, G. Scalia, R. Judele, E. Kapatsina, S. Sauer, A. Schreivogel, M. Tosoni, Discotic liquid crystals from tailor-made synthesis to plastic electronics. Angew. Chem. Int. Ed. 46, 4832-4887 (2007)... 

T. Kamei, T. Kato, E. Itoh, K Ohta, Discotic liquid crystals of transition metal complexes 47 synthesis of phthalocyanine-fullerene dyads showing spontaneous homeotropic alignment. J. Porphyrins Phthalocyanines 16, 1261-1275 (2012)... 

H.K. Bisoyi, S. Kumar, First examples of monodisperse discotic liquid crystal pentamers synthesis and mesomorphism. Tetrahedron Lett. 49, 3628-3631 (2008)... 

The intermolecular version of the Scholl reaction is much less prevalent in the literature due to the difficulty in controlling the formation of the desired products. Bushby and co-workers have used an intermolecular version of the Scholl reaction in efforts toward the synthesis of chirally discotic liquid crystals featuring the triphenylene nucleus. The fluorobenzene derivative 20 was coupled with the symmetric biphenyl 19 to... 

As mentioned in chapter 3, the synthesis of discotic materials in which the peripheral units are different is quite difficult and general synthetic routes to such systems are only just becoming available. Accordingly, early chiral discotic liquid crystals have a structure where all of the peripheral units are chiral e.g compound 18). 

The main-chain and side-chain polymers as well as the classical small-molecule liquid crystals consist essentially of one-dimensional molecules (rods). Low molar mass compounds of two-dimensional discshaped molecules were discovered by Chandrasekhar (1977) to possess liquid crystallinity. They were referred to as discotic liquid crystals. Later research has involved the synthesis and characterization of polymers with discotic moieties connected via flexible spacer groups. 

Kumar, S. Pal, K. S. Synthesis and characterization of novel imidazolium-based ionic discotic liquid crystals with a triphenylene moiety. Tetrahedron Lett. 2005, 46, 2607-2610. Yazaki, S. Kamikawa, Y Yoshio, M. Hamasaki, A. Mukai, T. Ohno, H. Kato, T. Ionic liquid crystals Self-assembly of imidazo-lium salts containing an L-glutamic acid moiety, Chem. Lett. 2008, 37, 538-539. 

Some partially (2,3,5,6-) acylated derivatives of hexahydroxybenzene have also been found to exhibit discotic liquid crystal phases, as have the related tetraesters of 2,3,5,6-tetrahydroxy-l,4-benzoquinone [11]. Their synthesis, shown in Scheme 2, is relatively straightforward. 2,3,5,6-Tetra-hydroxy-l,4-benzoquinone [12] is acylated with an excess of the acid chloride in refluxing pyridine. Neutral work-up yields the quinone, whereas the hydroquinone is iso-... 

Scheme 13. Synthesis of Anthracene (Rufigallol) based discotic liquid crystals. Reagents (a) 98% H2S04/100°C/2h [36] (b) Ac20/trace H2S04/re-flux/2 h [36] (c) pyridine/boil [36] (d) H [36] (e) RBr/Na2CO3/DMF/160 C/16h [38] (f)RCOCI/ pyridine-acetone/40°C/l h [37].

Discotic liquid crystals of phenylacetylene macrocycles 29 were first reported by Zhang and Moore in 1994 [136]. Their synthesis involves the stepwise build-up of phenylacetylene hexamers [137] followed by a macrocyclization step [138]. The key reactions of the synthesis (Scheme 33) are the palladium-catalysed coupling of aryl iodides and acetylenes, and the selective deprotection steps allowing the ends of the growing oligomer to be distinguished. The synthesis shown is just one of the many possible sequences that can be used to prepare the macrocycles. The mesophase behaviour of the discotic derivatives prepared to date is shown in Table 35 [136]. In some ways... 

Laschat S, Baro A, Steinke N, Giesselmann F, Hagele C, Scalia G, Judele R, Kapatsina E, Sauer S, Schreivogel A, Tosoni M (2007) Discotic liquid crystals from tailor-made synthesis to plastic electronics. Angew Chem hit Ed 46 4832 887... 

Cammidge, A. N. Bushby, R. J. Synthesis and structural features of discotic liquid crystals. Handbook of Liquid Crystals 1998, 2B, 693-748. 

Recently, Kita demonstrated the efficient synthesis of hexahydro3q7-triphenylene (49) discotic liquid crystals, under simple and mild reaction conditions with catechol, PIDA, and methanesulfonic acid (Scheme 8.17). ... 

Henderson, P., Ringsdorf, H., Schuhmacher, P. Synthesis of functionalized triphenylenes and dibenzopyrenes precursor molecules for polymeric discotic liquid crystals, liq. Cryst. 18, 191-195 (1995)... 

Kumar, S., Schuhmacher, R, Henderson, R, Rego, J., Ringsdorf, H. Synthesis of new functionalized discotic liquid crystals for photoconducting applications. Mol. Cryst. Liq. Cryst. 288, 211-222(1996)... 

Kumar, S. Pal, S. K (2005). Synthesis and characterization of novel imidazolium-based ionic discotic liquid crystals with a triphenylene moiety. Tetrahedron Lett, 46, 2607-2610. 

The formation of liquid crystals (LC) from suitably functionalized acetylenic SPMs has often been the motivation for their synthesis. A number of groups have sought to capitalize on the planar or nearly planar disk-like geometry of SPMs to promote the formation one-dimensional columnar stacks based on a combination of n-n stacking, van der Waals, dipole, and hydrophobic interactions. For example, Heiney, Moore, and coworkers have reported the high-resolution X-ray diffraction analysis (XRD) of a tubular, discotic LC based on SPM 133, which has been synthesized via a Sonogashira reaction [106]. These studies reveal an unanticipated distortion and... 

Isocyanides are excellent ligands for Pd (II) and Pt(II), to the point that they can be used in the synthesis of thermotropic liquid crystals. Some [MX2 (isocyanide)2] complexes are liquid crystals (discotic) at room temperature. The thermal properties depend very much on the cis or trans geometry of the complex. For X = I, the trans geometry is favored, whereas for X = Cl, cis complexes are formed. 

There are relatively few reports of liquid crystal dimers containing discotic mesogenic units [105-112] and this has been due in large part to the difficulties in preparing monofunctionalised discotic precursors. Without such monofunctional precursors the preparation of discotic dimers often involves laborious separation procedures involving several isomers of the discotic core. In recent years, however, there have been many advances in the synthesis of triphenylene-... 

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