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Macrocyclic Receptors Synthesis, History, Binding Mechanism: An Update on Current Status
Published in Satish Kumar, Priya Ranjan Sahoo, Violet Rajeshwari Macwan, Jaspreet Kaur, Mukesh, Rachana Sahney, Macrocyclic Receptors for Environmental and Biosensing Applications, 2022
Satish Kumar, Priya Ranjan Sahoo, Violet Rajeshwari Macwan, Jaspreet Kaur, Mukesh, Rachana Sahney
Qiao et al. developed isopropylphenyl based bulky cyanostar receptor (54) in four synthetic steps using Miyaura borylation and Suzuki-Miyaura cross-coupling, oxidation reaction using pyridinium chlorochromate (Scheme 31). The final step includes the reaction of aldehyde precursor with Cs2CO3, where the reaction was facilitated further with a template such as a tetrabutylammonium iodide (TBAI) and produced the receptor 54 in 40% yield (Qiao et al. 2016).
Oxidation Reactions
Published in Michael B. Smith, A Q&A Approach to Organic Chemistry, 2020
Pyridinium chlorochromate (PCC) and pyridinium dichromate (PDC) are Cr(VI) reagents that have been structurally modified to diminish their oxidizing power and improve their solubility in organic solvents. The structures are shown in the figure. Note that pyridinium is the conjugate acid of the reaction of pyridine and a Brønsted–Lowry acid. See Section 16.6 for a discussion of heteroaromatic compounds such as pyridine.
Columnar mesomorphism from a new luminescent thiazolo[5,4-d]thiazole-based core
Published in Liquid Crystals, 2021
Arthur B. de S. Santos, Edivandro Girotto, Cristian A.M. Salla, Ivani Malvestiti, Eduardo H L Falcão, Ivan H. Bechtold, Hugo Gallardo
First, alcohol 3 (2.1 g, 9.37 mmol) and 50 mL of CH2Cl2 were place into a 100 mL flask. Pyridinium chlorochromate (PCC) (4.0 g, 18.7 mmol) was added slowly and the reaction mixture stirred at room temperature for 12 hours. The mixture was filtered off in celite and washed with CH2Cl2, the solvent was evaporated in the rotatory evaporator. The crude product was purified by column chromatographic on silica with a mixture of hexane:ethyl acetate (7:3) as eluent affording 2.04 g of 4 (yield 98%). 1 H NMR (CDCl3, 400 MHz, ppm): δ = 4.00 (s, 6 H, -OCH3); 8.72 (m, 2 H, -Ar-H); 8.92 (m, 1 H, -Ar-H); 10.13 (s, 1 H, -CHO). 13 C NMR (CDCl3, 100 MHz, ppm): δ = 52.9; 132.0; 134.5; 135.9; 137.0; 165.3; 190.5.
Recent advancements in the mesogens comprising of 1,3,5-triazine core moiety
Published in Liquid Crystals Reviews, 2019
Veerabhadraswamy et al. [83] synthesized the a novel series of C3-symmetric molecules having electron-accepting s-triazine as a core and electron-donating styrylbenzene arms. The expected C3 symmetric disc-type molecules, 166a-k, acquired from the 2,4,6-triphenyl-1,3,5-triazine core, were synthesized by the path depicted in Scheme 21. By treating 3,4-dihydroxybenzaldehyde (156) and 4-hydroxybenzaldehyde (147) with 1-bromodecane in DMF solvent in the presence of anhydrous K2CO3 yields the respective O-alkylated products, viz, 3,4-bis(n-decyloxy)benzaldehyde (157) and 4-(n-decyloxy)benzaldehyde (155) [84]. Starting from gallic acid (158), the compounds 3,4,5-Tris(n-alkoxy)benzaldehydes (162a-i) were prepared [85], using ethanol gallic acid (158) was first esterified to get ethyl 3,4,5-trihydroxybenzoate (159) [85], and this was then treated with different 1-bromoalkanes under Williamson’s etherification reaction conditions to get O-alkylated products i.e. ethyl 3,4,5-tris(n-alkoxy)benzoates (160a-i) [85]; these esters were reduced using lithium aluminum hydride (LAH) in THF to yield 3,4,5-tris(n-alkoxy)-benzylalcohols (161a-i) [85], which were then oxidized using pyridinium chlorochromate (PCC) in methylene dichloride (MDC) to get the required benzaldehydes 162a-i [85]. Treating 4-(Bromomethyl) benzonitrile (163) with trifluoromethane-sulfonic acid provided a cyclotrimerized product i.e. 2,4,6-tris(4-(bromo-methyl)phenyl)−1,3,5-triazine (164) [86]; the hexamethyl (4,4′,4′′-(1,3,5-triazine-2,4,6-triyl)tris-(4,1-phenylene))tris-(methylene)triphosphonate (165) was obtained by the Arbuzov reaction between triazine and trimethyl phosphite [87]. Under Horner–Wadsworth–Emmons conditions, aldehydes, 155, 157, and 162a-i, were reacted with the triphosphonate 165 in the last step of the synthetic pathway to obtain the target 166a-k compounds. Investigation of the mesogenic properties by various complementary approaches evidenced for self-assembly into a hexagonal columnar mesophase, existing over a reasonable and wide range of temperatures. Both in fluid/frozen columnar states and in solution, the photophysical properties were investigated by photoluminescence and UV/Vis absorption spectroscopy. The emission spectra acquired as a temperature function rule out the collapse of larger columns and a non-radiative, thermally triggered technique. Thin films of the glassy columnar condition were investigated, which accounts for defect-free orientation, freezing ionic species, and conserved fluorescence, with the aid of atomic force microscopy images (AFM images), indicated a homogeneous granular morphology containing fibrillar structures. Raman spectroscopy clearly showed the dissimilarities in the birefringence and surface morphology of thin films of the solid and frozen columnar conditions. Electrochemical study divulged that LUMO energy of −4.0 eV. Consequently, these discotic patterns satisfy certain criteria of organic materials, which are necessary for generating electronic tools.