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Interfacial Catalysis at Oil/Water Interfaces
Published in Alexander G. Vdlkdv, Interfacial Catalysis, 2002
The azo coupling between diazonium ions and coupling components is an important reaction for synthesizing dye compounds [29,30]. Usually, this reaction proceeds in a homogeneous solution phase. However, in certain cases, the reaction in a two-phase system is advantageous, as many coupling components are lipophilic, while diazonium ions are relatively hydrophilic [31]. The two-phase azo coupling of this type is facilitated by the reverse-PTC in which hydrophilic cations are transferred from W to O by ionpairing with large hydrophobic anions [32-40], e.g., tetrakis[3,5-bis(trifluoromethyl)phenyl] borate anion [36,37]. Kong et al. recently used the phase-boundary potential-driven ion transfer of arenediazonium ions from W to 1,2-dichloroethane (DCE), instead of using phase-transfer catalysts, to effect the two-phase azo-coupling reactions [11].
Synthesis and physico-chemical properties of dilateral flouro azo/ester four aromatic ring mesogens and their mixtures of liquid crystals
Published in Liquid Crystals, 2023
Mohamed H. Ali, Gamal R. Saad, Nagwa H.S. Ahmed, Abdelgawad A. Fahmi
The general procedure for the synthesis of the intermediates and final products is given in Scheme 1. The intermediates derivatives A, Bn, An and BX were prepared according to the methods described before [42]. Compound Ethyl-4-hydroxy-3-F-substituted phenylazobenzoate (A) was prepared through azo coupling reaction between ethyl-4-aminobenzoate and -flouro phenol. Compounds 4-n-alkoxy 3-F phenylazo benzoic acids (An) were prepared from reaction between compound A and n-bromo alkane by Williamson etherification followed by acid hydrolysis. 4-Substituted phenylazo-3-flouro phenol (Bx) was prepared via azo coupling reaction between 4-substituted aniline and 3-flouro phenol. Finally, 4-substituted phenylazo-3- flouro phenyl-4′-n-alkoxy 3-flouro phenylazobenzoates (Ina-d) were synthesised by condensing equimolar amounts of 4-alkoxy 3-flouro phenylazo benzoic acids (An) and 4-substituted phenylazo-3-flouro phenol (Bx) using dicyclohexyl carbodiimide (DCC), as a condensing agent, 4-dimethyl amino pyridine, as a catalyst, and CH2Cl2 as a solvent. The reaction mixture was stirred at room temperature for 3 days. The solvent was distilled off and the residue crystallised twice from ethanol. Final products were filtered, washed and dried. The purity of the final products was checked with TLC.