ChemInform Abstract: Synthesis of Calamitic Liquid Crystals by Transition Metal Catalyzed Cross‐Coupling Reaction

Abstract

ChemInform Abstract (63 refs.).

The liquid‐crystalline derivatives of 3,6‐disubstituted cyclohex‐2‐enones

“…The detailed investigations of the reaction conditions of the preparation of substituted cyclohex-2-enones have shown that the mesomorphic 3,6-disubstituted cyclohex-2enones (11) with different combinations of cyclic, bridge, terminal fragments and lateral substituents can be prepared in a yield 60-80% and in a short way by the condensation of the corresponding Mannich salts or 2-chloro(bromo)ethylaryl(alkyl)-ketones with 2-substituted acetoacetic esters, 4substituted methyl-benzylketones, or analogous ketones and β-dicarbonylic compounds in the presence of potassium carbonate, potassium hydroxide and phase catalysts in a boiling diglyme or dioxane. 32,33 For example, the 3,6-disubstituted cyclohex-2-enones of the following structures (12)(13)(14)(15)(16)(17)(18)(19)(20)(21)(22)(23)(24)(25) have been prepared using these starting materials and the reaction conditions. n, m = 1-10; Y 1,2,3,4 = H, F, Cl.…”

“…[14][15][16][17] The LC derivatives of phenylcyclohexane are synthesized using the Nenitzescu method or Grignard reaction. 18 Grignard or the cross-coupling and Friedel-Crafts reactions are also used for the preparation of LC biphenylcyclohexane or biphenyl-cyclohexene derivatives or other three-and four-rings liquid-crystalline compounds; for example, derivatives of dicyclohexylphenyl (4) and 4,4′-dicyclohexylbiphenyl (5), [19][20][21][22] which are very important components of the compositions with a wide temperature range of the nematic phase. Unfortunately, these methods do not allow the synthesise of such compounds with a high yield and without the formation of by-products.…”

Polyfunctional intermediates for the preparation of liquid-crystalline and anisotropic materials

“…From lots of the 3,6-disubstituted cyclohex-2-enones (I), trans-2,5-disubstituted cyclohexanones (II) and their derivatives, which have been synthesised and investigated, we have to described the following: (A) Substituted cyclohexenes (1, 2, 7; 8a-d), fluorocyclohexenes (9a-d) and fluorocyclohexanes (4,6), which are characterised a low optical anisotropy and viscosity, and a low temperature formation of the nematic phase (Scheme 6; Tables 1 and 2). [30][31][32][33] (B) Lateral substituted p-terphenyls, p-quaterphenyls and p-quinquephenyls (10-17), which, as our investigations have shown [34][35][36][37], are easily formed in a one-stage procedure from the corresponding 3,6-disubstituted cyclohex-2-enones (I.3) (Scheme 7).…”

“…[1][2][3][4][5][6][7][8][9][10][11] Unfortunately, the methods for the preparation of arylboronic acids, Grignard reagents from 4-bromo-1-(trans-4-alkylcyclohexyl)benzenes or 4-bromo-4-substituted biphenyls and 4-(4-substituted phenyl)cyclohexanones and 4-(trans-4-substituted cyclohexyl)cyclohexanones from the corresponding 4-substituted benzylmethylketones, 1,4-cyclohexanedione, or from the adducts of the condensation of corresponding 2-substituted 1,3-butadienes with 4-substituted styrenes are usually complicated and are characterised by a low yield of the products. [12][13][14] It has been reported that the mesomorphic derivatives of benzene, cyclohexane, biphenyl or terphenyl, which are useful components of LC mixtures for display applications, can be easily prepared in a high yield from the corresponding 3,6-disubstituted cyclohex-2-enones [15][16][17][18][19][20].…”