Regioselective Substitution of BINOL

1,1'-Bi-2-naphthol (BINOL) has been extensively used as the chirality source in the fields of molecular recognition, asymmetric synthesis, and materials science. The direct electrophilic substitution at the aromatic rings of the optically active BINOL has been developed as one of the most convenient strategies to structurally modify BINOL for diverse applications. High regioselectivity has been achieved for the reaction of BINOL with electrophiles. Depending upon the reaction conditions and substitution patterns, various functional groups can be introduced to the specific positions, such as the 6-, 5-, 4-, and 3-positions, of BINOL. Ortho-lithiation at the 3-position directed by the functional groups at the 2-position of BINOL have been extensively used to prepare the 3- and 3,3'-substituted BINOLs. The use of transition metal-catalyzed C-H activation has also been explored to functionalize BINOL at the 3-, 4-, 5-, 6-, and 7-positions. These regioselective substitutions of BINOL have allowed the construction of tremendous amount of BINOL derivatives with fascinating structures and properties as reviewed in this article. Examples for the applications of the optically active BINOLs with varying substitutions in asymmetric catalysis, molecular recognition, chiral sensing and materials are also provided.

Dynamic Thermodynamic Resolution of Racemic 1,1'-Binaphthyl-2,2'-diol (BINOL)

A dynamic thermodynamic resolution method for converting (R/S)-BINOL (1,1'-binaphthyl-2,2'-diol) into (R)-BINOL in 100% theoretical yield is reported. This technique involves mixing (R/S)-BINOL with N-benzyl cinchonidinium bromide (1 equiv) and a [Cu2(tmeda)2(μ-OH)2]Br2 (2.5 mol %) redox catalyst in acetonitrile. In the background of this process is the observation that the energy for atropoisomerization decreases significantly when an electron is removed from BINOL. Therefore, it is possible to convert both enantiomers into the thermodynamically favorable [N-benzyl cinchonidinium bromide·(R)-BINOL] adduct.

Novel π-expanded chrysene-based axially chiral molecules: 1,1′-bichrysene-2,2′-diols and thiophene analogs

1,1′-Bichrysene-2,2′-diol and its thiophene analogs, 6,6′-biphenanthro-[1,2- b]thiophene-7,7′-diols, as a series of novel π-expanded chrysene-/phenanthro[1,2- b]thiophene-based axially chiral molecules are synthesized from 1,1′-bi-2-naphthols with key steps including a Suzuki coupling, a Wittig reaction, and acid-mediated cyclization.

Remarkable adsorptive removal of nitrogen-containing compounds from hydrotreated fuel by molecularly imprinted poly-2-(1H-imidazol-2-yl)-4-phenol nanofibers

Molecularly imprinted polymer (MIP) nanofibers were prepared by the electrospinning of poly 2-(1H-imidazol-2-yl)-4-phenol (PIMH) in the presence of various nitrogen containing compounds (N-compounds). Molecularly imprinted polymer nanofibers show selectivity for various target model nitrogen-containing compounds with adsorption capacities of 11.7 ± 0.9 mg g^-1, 11.9 ± 0.8 mg g^-1 and 11.3 ± 1.1 mg g^-1 for quinoline, pyrimidine and carbazole, respectively. Molecular modelling based upon density functional theory (DFT) indicated that hydrogen bond interactions may take place between the lone-pair nitrogen atom of model compounds (quinoline and pyrimidine) and the -OH and -NH groups of the PIMH nanofibers. The adsorption mode followed the Freundlich (multi-layered) adsorption isotherm, which indicated possible nitrogen-nitrogen compound interactions. Molecularly imprinted polymer nanofibers show potential for the removal of nitrogen-containing compounds in fuel.

Adsorptive denitrogenation of fuel over molecularly imprinted poly-2-(1H-imidazol-2-yl)-4-phenol microspheres

Molecularly imprinted poly 2-(1H-imidazol-2-yl)-4-phenol prepared by suspension polymerization of 2-(1H-imidazol-2-yl)-4-vinylphenol in the presence of selected nitrogen containing compounds showed adsorption selectivity for target nitrogen-containing compounds in fuel oil.