Bi-2-naphthol Research Articles

A convenient fluorescent method to simultaneously determine the enantiomeric composition and concentration of functional chiral amines.

A 1,1'-bi-2-naphthol (BINOL)-based chiral aldehyde in combination with Zn(II) shows a highly enantioselective fluorescent response toward functional chiral amines at λ>500 nm. However, the combination of salicylaldehyde and Zn(II) gives the same fluorescent enhancement for both enantiomers of a functional chiral amine at λ=447 nm. By using the fluorescent responses of the combination of the BINOL-based chiral aldehyde, salicylaldehyde and Zn(II) at the two emission wavelengths, both the concentration and enantiomeric composition of functional chiral amines such as amino alcohols, diamines, and amino acids can be simultaneously determined by a single fluorescent measurement. This work provides a simple and convenient method for chiral assay.

Static and dynamic properties of 1,1'-bi-2-naphthol and its conjugated acids and bases.

Several convergent techniques were used to characterize 1,1'-bi-2-naphthol (BINOL) and some of its properties. Its acidity in the gas-phase, from neutral species to monoanion, was measured by mass spectrometry. The conformation and structure of BINOL in the gas phase was determined by microwave rotational spectroscopy. NMR experiments in fluorosulfonic acid established that BINOL was monoprotonated on one of the hydroxyl oxygen atoms. The enantiomerization barriers reported in the literature for BINOL under neutral, basic, and acid conditions were analyzed with regard to the species involved. Finally, DFT calculations allowed all of these results to be gathered in a coherent picture of the BINOL structure.

ChemInform Abstract: Magnesium Complexes as Highly Effective Catalysts for Conjugate Cyanation of α,β‐Unsaturated Amides and Ketones.

Asymmetric cyanation of trimethylsilyl cyanide (TMSCN) with α,β-unsaturated amides and ketones, respectively, catalyzed by bifunctional mononuclear 1,1′-bi-2-naphthol (BINOL)–Mg and binuclear bis(prophenol)–Mg catalysts was realized. A series of synthetically important 1,4-cyano products were obtained with good to high enantioselectivities (up to 97 % ee).

Investigation of the Mitsunobu Reaction of BINOL and Cinchona Alkaloids: Inversion or Retention of Configuration?

An efficient approach toward the construction of multistereogenic binaphthol (BINOL)–derived alkaloids with C2-axial and sp3 central chirality has been accomplished. The reaction of BINOL and cinchona alkaloids was occurred smoothly under the Mitsunobu conditions, which led to the synthesis of a new family of complicated functional molecules based on chiral BINOL and cinchona alkaloids. In addition, on the basis of the experimental results, we provided a possible explanation for the intramolecular tertiary amine-induced retention of configuration at C9 of cinchona alkaloids while the inversion of configuration was observed with general alcohols under classic Mitsunobu conditions.

ChemInform Abstract: Chiral 1,1′‐Binaphthyl‐2,2′‐disulfonic Acid (BINSA) and Its Derivatives for Asymmetric Catalysis

AbstractReview: [37 refs.

Rapid optical methods for enantiomeric excess analysis: from enantioselective indicator displacement assays to exciton-coupled circular dichroism.

CONSPECTUS: The advent of high-throughput screening (HTS) for chiral catalysts has encouraged the development of fast methods for determining enantiomeric excess (ee). Traditionally, chromatographic methods such as chiral HPLC have been used for ee determination in HTS. These methods, however, are not optimal because of high duty cycle. Their long analysis time results in a bottleneck in the HTS process. A more ideal method for HTS that requires less analysis time such as chiroptical methods are thus of interest. In this Account, we summarize our efforts to develop host-guest systems for ee determination. The first part includes our enantioselective indicator displacement assays (eIDAs), and the second part focuses on our circular dichroism based host-guest systems. Our first eIDA utilizes chiral boronic acid receptors, along with prescreened indicators, to determine ee for chiral α-hydroxyacids and vicinal diols with ±7% average error (AE). To further the practicality for this system, a HTS protocol was developed. Our second eIDA uses diamino chiral ligands and Cu(II) as the receptor for the ee determination of α-amino acids. The system reported ±12% AE, and a HTS protocol was developed for this system. Our first CD based host-guest system uses metal complexes composed of Cu(I) or Pd(II) with enantiopure 2,2'-diphenylphosphino-1,1'-binaphthyl (BINAP) as host to determine the ee of chiral vicinal diamines (±4% AE), primary amines (±17% AE), and cyclohexanones (±7% AE). Primary amines and cyclohexanones were derivatized to form chiral imines or chiral hydrazones to allow coordination with the metal complex. Upon coordination of chiral analytes, the metal-to-ligand (BINAP) charge transfer band was modulated, thus allowing the discrimination of chiral analytes. As an effort to improve the accuracy for chiral primary amine ee determination, a system with a host composed of o-formylphenyl boronic acid (FPBA) and enantiopure 1,1'-bi-2-naphthol (BINOL) was used to reduce the AE to ±5.8%. In the presence of amines, the FPBA-BINOL host forms an imine-coordinated boronic ester, thus affecting the CD signal of the boron complex. Another chiral primary amine ee determination system was developed with Fe(II) and 3-hydroxy-2-pyridinecarbaldehyde. The chiral imines, formed by the pyridinecarbaldehyde and chiral amines, would coordinate to the Fe(II) ion yielding exciton-coupled circular dichroism (ECCD) active metal complexes. This system was able to determine the ee of chiral amines with ±5% AE. Furthermore, this imine-Fe(II) complex system also successfully determined the ee of α-chiral aldehydes with ±5% AE. Other ECCD based hosts were subsequently developed; one with bisquinolylpyridylamine and Cu(II) for chiral carboxylates and amino acids and another multicomponent system with pyridine chromophores for chiral secondary alcohol ee determination. Both of the systems were able to determine ee of the chiral analytes with ±3% AE. Overall, our group has developed ee determining host-guest systems that target various functionalities. To date, we are able to determine the ee of vicinal diols, α-hydroxyacids, vicinal diamines, cyclohexanones, amines, α-chiral aldehydes, carboxylates, amino acids, and secondary alcohols with ±7% or lower average error. Future development will involve improving the average error and employing the current systems to analyze real-life samples resulting from parallel syntheses.

Enantioselective haloetherifications catalyzed by 1,1'-bi-2-naphthol (BINOL) phosphates: from symmetrical alkenediols to simple alkenols.

Asymmetric haloetherifications can be conducted using 1,1'-bi-2-naphthol (BINOL) phosphates as catalyst. In combination with simple N-haloamides such as N-iodopyrrolidinone or N-bromosuccinimide, good enantioselectivities can be achieved. However, depending on the substrate, the choice of BINOL phosphate is important, and different catalysts show remarkably different selectivities.

Magnesium Complexes as Highly Effective Catalysts for Conjugate Cyanation of α,β‐Unsaturated Amides and Ketones

Asymmetric cyanation of trimethylsilyl cyanide (TMSCN) with α,β-unsaturated amides and ketones, respectively, catalyzed by bifunctional mononuclear 1,1'-bi-2-naphthol (BINOL)-Mg and binuclear bis(prophenol)-Mg catalysts was realized. A series of synthetically important 1,4-cyano products were obtained with good to high enantioselectivities (up to 97 % ee).

Hydrogen bonding or deprotonation: on fluoride ion fluorescence sensing with 1,1′-bi-2-naphthol derivatives

The isolation and structural characterisation of two ionic complexes (S)-3 and(S)-4 based on fluoride ion-mediated deprotonation of 1,1′-bi-2-naphthol (BINOL) derivatives (S)-1 and (S)-2 have been carried out for the first time. X-ray crystallographic study showed that the deprotonated forms (S)-3 and (S)-4 adopt remarkably different molecular geometries, bond parameters as well as molecular packing modes from their neutral analogs, in agreement with their significant fluorescence changes upon the addition of fluoride ion, giving insights into the actual mechanism of fluoride ion fluorescence sensing. The deprotonation–protonation processes in two BINOL derivatives were also investigated by both fluorescence measurements and X-ray structural analyses. Such chiral basic compounds can be promising organocatalysts for asymmetric reactions.

Chiral 1,1′‐Binaphthyl‐2,2′‐Disulfonic Acid (BINSA) and Its Derivatives for Asymmetric Catalysis

AbstractChiral Brønsted acid catalysts, which are derived from commercially available (R)‐ or (S)‐ 1,1′‐bi‐2‐naphthol (BINOL), have found widespread application as chiral organocatalysts and chiral ligands for metal species. The Brønsted acidity of these catalysts is considered to be associated with their catalytic activity. Therefore, due to the rapid development of asymmetric organocatalysis, chiral 1,1′‐binaphthyl‐2,2′‐disulfonic acid (BINSA) and the corresponding chiral binaphthyl disulfonimides are highly attractive as stronger chiral Brønsted acid catalysts than carboxylic acids, phosphoric acids, and phosphoramides. This Focus Review summarizes the latest achievements in chiral BINSA chemistry, particularly in the field of asymmetric organocatalysis.

Asymmetric photoreaction of a diarylethene in hydrogen-bonded cocrystals with chiral molecules

A photochromic diarylethene having 2-methyl-4-pyridyl groups formed chiral cocrystals with (R)- or (S)-1,1'-bi-2-naphthol (BINOL). X-ray crystal structure analysis revealed that the diarylethene forms O-H···N type hydrogen bonds with BINOL and the central hexatriene moiety is fixed in P- or M-helix conformation in the cocrystals. The diarylethene molecules underwent reversible cyclization reactions in the single-component crystal as well as in the cocrystals upon alternate irradiation with ultraviolet (UV) and visible light. In the chiral cocrystals, a highly enantioselective photocyclization reaction took place owing to the conformational confinement.

Asymmetric alkyne addition to aldehydes catalyzed by Schiff bases made from 1,1′-bi-2-naphthol and chiral benzylic amines

Several 1,1′-bi-2-naphthol (BINOL)-based Schiff bases were prepared from the condensation of (R)-3,3′-diformyl BINOL with chiral benzylic amine derivatives. These compounds were used to catalyze the reaction of phenylacetylene with aldehydes in the presence of ZnEt2 with up to 85% ee and 83% yield.

Broadband spectroscopy with external cavity quantum cascade lasers beyond conventional absorption measurements

Laser spectroscopy is a powerful tool for analyzing small molecules, i.e. in the gas phase. In the mid-infrared spectral region quantum cascade lasers (QCLs) have been established as the most frequently used laser radiation source. Spectroscopy of larger molecules in the gas phase, of complex mixtures, and analysis in the liquid phase requires a broader tuning range and is thus still the domain of Fourier transform infrared (FTIR) spectroscopy. However, the development of tunable external cavity (EC) QCLs is starting to change this situation. The main advantage of QCLs is their high spectral emission power that is enhanced by a factor of 10(4) compared with thermal light sources. Obviously, transmission measurements with EC-QCLs in strongly absorbing samples are feasible, which can hardly be measured by FTIR due to detector noise limitations. We show that the high power of EC-QCLs facilitates spectroscopy beyond simple absorption measurements. Starting from QCL experiments with liquid samples, we show results of fiber evanescent field analysis (FEFA) to detect pesticides in drinking water. FEFA is a special case of attenuated total reflection spectroscopy. Furthermore, powerful CW EC-QCLs enable fast vibrational circular dichroism (VCD) spectroscopy of chiral molecules in the liquid phase - a technique which is very time consuming with standard FTIR equipment. We present results obtained for the chiral compound 1,1'-bi-2-naphthol (BINOL). Finally, powerful CW EC-QCLs enable the application of laser photothermal emission spectroscopy (LPTES). We demonstrate this for a narrowband and broadband absorber in the gas phase. All three techniques have great potential for MIR process analytical applications.

Chiral Cu(ii)-amino alcohol based complexes for asymmetric aza-Henry reaction of N-Ts imines

A series of chiral dimeric ligands 1A–C, 2A–B, 3A–B and 4A derived from (S)/(R) 1,1′-bi(2-naphthol)-bis-aldehyde/piperazine-bis-aldehyde and various aminoalcohols viz., (1R,2S)-(−)-2-aminodiphenylethanol, (1S,2R)-(−)-2-aminodiphenylethanol, (1R,2S)-1-amino-2,3-dihydro-1H-inden-2-ol and (R)-valinol were synthesized. In situ generated complexes 1A–C–, 2A–B–, 3A–B–, 4A–Cu(II)/Cu(I) of dimeric chiral ligands with different copper salts were used as catalysts for the asymmetric aza-Henry reaction of a variety of N-tosylimines as substrates with different nitroalkanes at RT to afford good yields of aza-Henry products (80% with respect to the imines) with excellent enantioselectivity (ee > 99%) in 24 h with nitromethane and high syn selective products with excellent enantioselectivity with nitroethane. The dimeric chiral Cu(II) complex 1A–Cu(II) retained its performance at the gram level and was expediently recycled for a number of times. The enantio-pure aza-Henry product was further used for the synthesis of (S)-levamisole (an anthelminthic agent) in good yield and ee in three steps.

(S)-BINOL-based boronic ester fluorescence sensors for enantioselective recognition of α-phenylethylamine and phenylglycinol

Four chiral fluorescence sensors (S)-L1–4 incorporating boronic ester and (S)-1,1′-bi-2-naphthol (BINOL) moieties were synthesized and developed for the enantioselective recognition of α-phenylethylamine and phenylglycinol enantiomers. The sensor (S)-L1 shows an obvious fluorescence quenching “turn-off” response towards enantiomers of both α-phenylethylamine and phenylglycinol. Interestingly, the sensor (S)-L2 can exhibit remarkable fluorescent enhancement “turn-on” response behavior towards (S)-α-phenylethylamine, but shows no response towards phenylglycinol enantiomers. The Stern–Volmer constant (Ksv) values of (S)-L1 are 0.63 × 103 L mol−1 and 4.48 × 103 L mol−1 for (L)- and (D)-phenylglycinol, respectively, and the value of the enantiomeric fluorescence difference ratio (ef) of (S)-L2 is 4.6 for α-phenylethylamine, demonstrating that (S)-L2 could be used as a fluorescence sensor for simple and direct visual discrimination of organic molecule enantiomers. On the contrary, no fluorescence enantioselective recognition response could be observed when using the (S)-BINOL-based boronic ester sensors (S)-L3 and (S)-L4 incorporating bigger naphthyl or 8-methoxyquinolinyl substituent groups.

ChemInform Abstract: Iron‐Catalyzed Oxidative Cross‐Coupling of Phenols and Alkenes.

A novel bioinspired iron-catalyzed oxidative cross-coupling reaction between phenols and conjugated alkenes was developed. This method enables the direct coupling of phenols with styrene, α-alkyl- and α-arylstyrenes, β-alkyl styrenes, and stilbenes, thereby providing a new strategy for the preparation of the pharmacologically important 2,3-dihydrobenzofuran motif. In addition, this study revealed that under a different set of conditions an oxidative/addition dearomatization reaction of 1,1′-bi-2-naphthol (BINOL) with styrene can take place.

Fluorescent BINOL-based sensor for thorium recognition and a density functional theory investigation

A novel 1,1′-bi-2-naphthol (BINOL) derivative fluorescence sensor L-1 for the recognition of thorium ion with a fluorescence quench response. This ligand showed high selectivity and sensitivity for thorium ion recognition. Coordination effects were investigated by DFT calculations, and the coordination modes and sites were confirmed. Moreover, the coordination abilities of the L-1 ligand with Th4+ and UO22+ were evaluated.

Efficient Routes to Racemic and Enantiomerically Pure (S)-BINOL Diesters

A systematic study for esterification procedures to the synthesis of BINOL diesters is described. Reaction conditions with trifluoracetic acid anhydride (TFAA) and 85% H3PO4 were selected as the best procedure to prepare enantiomerically pure (S)-1,1′-bi-2-naphthol (BINOL) diesters VIII to XI with almost quantitative yields and very short reaction times. [Supplementary materials are available for this article. Go to the publisher's online edition of Synthetic Communications® for the following free supplemental resources: Full experimental and spectral details.]

Lewis Acid Catalysis and Ligand Exchange in the Asymmetric Binaphthol-Catalyzed Propargylation of Ketones

1,1'-Bi-2-naphthol (BINOL)-derived catalysts catalyze the asymmetric propargylation of ketones. Density functional theory (DFT) calculations show that the reaction proceeds via a closed six-membered transition structure (TS) in which the chiral catalyst undergoes an exchange process with the original cyclic boronate ligand. This leads to a Lewis acid type activation mode, not a Brønsted acid process, which accurately predicts the stereochemical outcome observed experimentally.

Preparation and photocatalytic activity of fluoroalkyl end-capped vinyltrimethoxysilane oligomer/anatase titanium oxide nanocomposite-encapsulated low molecular weight aromatic compounds

Fluoroalkyl end-capped vinyltrimethoxysilane oligomer/anatase titanium oxide nanocomposite-encapsulated low molecular weight aromatic compounds [RF-(VM-SiO2)n-RF/an-TiO2/Ar-H] were prepared by the sol–gel reactions of the corresponding oligomer in the presence of anatase titanium oxide nanoparticles (an-TiO2) and the aromatic compounds such as bisphenol A [BPA], 1,1′-bi(2-naphthol) [BINOL], and fullerene under alkaline conditions. Thermogravimetric analyses measurements show that RF-(VM-SiO2)n-RF/an-TiO2 nanocomposite-encapsulated BPA and BINOL, in which the theoretical contents in the composites are 25 ∼ 32 %, were found to give no weight loss corresponding to the contents of these aromatic compounds even after calcination at 800 °C. On the other hand, the corresponding nanocomposite-encapsulated fullerene exhibited weight loss behavior related to the presence of fullerene under similar conditions; however, UV–vis spectra showed the presence of the residual fullerene in the composites even after calcination. An-TiO2 in these fluorinated nanocomposites can keep its crystalline structure without phase transformation into rutile even after calcination at 1,000 °C, although the parent an-TiO2 nanoparticles underwent a complete phase transformation into rutile under similar conditions. Notably, RF-(VM-SiO2)n-RF/an-TiO2/Ar-H nanocomposites can give a good photocatalytic activity even after calcination at 1,000 °C for the decolorization of methylene blue under UV light irradiation. More interestingly, these fluorinated nanocomposites before and after calcination were found to exhibit a higher photocatalytic activity at the initial UV light irradiation from 1 to 3 min than that of the corresponding RF-(VM-SiO2)n-RF/an-TiO2 nanocomposites under similar conditions.