Binaphthyl Skeleton Research Articles

Synthesis and controlled radical polymerization of axially chiral monomers with a binaphthyl skeleton

Synthesis and controlled radical polymerization of axially chiral monomers with a binaphthyl skeleton

Synthesis and Optical Properties of Binaphthyl Derivatives with Comprehensive Introduction of Phenylethynyl Groups.

In this study, compounds with phenylethynyl (PE) groups introduced at all of the possible positions of the methylene-bridged structure of the 1,1'-bi-2-naphthol backbone (3-PE to 8-PE) were synthesized. Compounds with four or six phenylethynyl groups (3,6-PE, 4,6-PE, 5,6-PE, 6,7-PE, and 3,4,6-PE) were also synthesized. The key reaction for the synthesis of these compounds was the Sonogashira reaction using halogen scaffolds. The new transformation methods include (1) selective bromination of the 5-position of the binaphthyl skeleton and (2) bromination of the 6-position and then iodination of the 4-position, followed by the Sonogashira reaction of iodine at the 4-position and lithiation and protonation of bromine at the 6-position. The optical properties of the compounds were evaluated. The extension of the π system greatly differed depending on the position of the phenylethynyl group. 4-PE, 4,6-PE, and 3,4,6-PE, in which the phenylethynyl groups were introduced in the extended direction of the naphthalene linkage axis, showed longer absorption and emission wavelengths and higher fluorescence quantum yields than the other compounds. In circularly polarized luminescence measurements, 7-PE showed a relatively large glum value, an interesting finding that reverses the sense.

Axially Chiral Borinic Acid Catalysts: Design, Synthesis, and Application in Alkylative Desymmetrization of 1,2-Diols.

A novel chiral borinic acid (CBA), an organocatalyst possessing a binaphthyl skeleton, was designed and synthesized. The synthesis of CBA was achieved with a 72% yield in four steps starting with optically pure 1,1'-bi-2-naphthol. The asymmetric catalytic activity was investigated in the desymmetrization of meso-1,2-diol.

(Invited) Identification of a Self-Photosensitizing Hydrogen Atom Transfer Organocatalyst System

The carbon-hydrogen (C-H) bond is a fundamental chemical bond that constitutes organic molecules, and its direct conversion leads to highly efficient molecular synthesis. In recent years, the hydrogen atom transfer (HAT) catalysis using the energy of visible light, has been attracting attention. However, existing methods require the use of photoredox catalysts such as organic molecules with complex structures and expensive metal complexes. In this study, we developed an organocatalytic system that mimics the electron transfer process of enzymes in vivo and promotes functionalization of stable C-H bond without photoredox catalyst. We designed a thiophosphoric acid catalyst that contains both a redox-active binaphthyl moiety and a sulfur atom. We found that this catalyst forms charge-transfer complexes with electron-deficient heteroaromatics and catalytically produces thyil radical via multi-step electron transfer under visible light irradiation.Based on the above design, we decided to investigate the formation of active HAT catalytic species in the absence of photoredox catalysis by the Minisci-type reaction using aldehydes and N-heteroaromatic rings. The results of the study confirmed that 29% of the product was obtained when using binaphtyl thiophosphoric acid (TPA) catalyst, as expected. Yield improved to 80% when an electron-donating group was introduced to the binaphthyl skeleton to enhance the donor-acceptor interaction. Changing the binaphthyl skeleton and thiophosphoric acid moieties markedly reduced reactivity, indicating that the presence of a sulfur atom in addition to a rigid binaphthyl skeleton is essential for the efficient reaction progress. With this optimized condition, alkylation of N-heteroaromatic rings by C-H bond activation of alcohols was found to proceed. Dehydrogenation of alcohols and benzylation of imines were also successfully achieved by using N-heteroaromatic catalyst. The mechanism of the electron transfer process has been confirmed by spectroscopic and computational methods, and will be presented in detail in the lecture. Figure 1

Synthesis and properties of binaphthyl chiral thermally activated delayed fluorescence molecules using thioxanthone as acceptor

The currently reported axial chiral molecules based on the 3,3′-substitution of the binaphthyl skeleton are limited by intrinsic fluorescence properties, resulting in generally low device efficiencies (EQE < 5%) of related organic light emitting diodes (OLEDs). Herein, we designed and synthesized four pair of chiral binaphthyl enantiomers (R/S-1 − R/S-4) adopting acceptor-donor-donor-acceptor (ADDA) structure by introducing different thioxanthone modification groups on the 3,3′-position of 2,2′-dimethoxy-1,1′-binaphthalene. Among them, emitter R/S-2 and R/S-4 obtained by enhancing intramolecular charge transfer exhibited TADF characteristics due to relatively small ΔEST of 0.12 eV and 0.17 eV, and relatively moderate SOC matrix elements of 0.28 cm−1 and 0.10 cm−1 between the 1CT and 3LE states. The CD spectra of these enantiomers in diluted solutions showed perfect mirror images and reasonable gabs for small organic molecules (10−4–10−3). And the external quantum efficiencies (EQE) of 10.9% and 8.32% for device A and B based on emitter S-2 and S-4 were highest compared with currently reported axial chiral molecules based on the 3,3′-position substitution of binaphthyl skeleton, providing simple molecular design strategies to construct efficient CP-OLED device.

Heterogeneous simplified Maruoka phase-transfer catalyst tethered on poly(styrene-co-acrylamide) microsphere: Structure-activity relationship in enantioselective α-alkylation

The covalent immobilization of valuable simplified Maruoka catalyst onto poly(styrene-co-acrylamide)microsphere at different locations was developed for the first time through the copolymerization of Maruoka catalyst-functionalized styrene with styrene and acrylamide cross-linked by EGDMA. It was found the morphology, porous feature of microsphere and the anchor location of Maruoka catalyst were mainly responsible for the catalytic performance in heterogeneous α-alkylation. The catalyst poly[St-co-AA-co-(R)-11] with a rigid framework, where homogeneous (R)-11 was anchored at the 6, 6′-positions of binaphthyl skeleton, possessed the relatively larger surface area (33.5m2g−1) and pore volume (1.27cm3g−1) and displayed high yields (81–96%) and excellent enantioselectivities (96–97%ee) in enantioselective α-alkylation.

Chirality Relay in 2,2'-Substituted 1,1'-Binaphthyl: Access to Propeller Chirality of the Tricoordinate Boron Center.

It is a challenging issue to achieve propeller chirality for triarylboranes owing to the low transition barrier between the P and M forms of the boron center. Herein, we report a new strategy to achieve propeller chirality of triarylboranes. It was found that the chirality relay from axially chiral 1,1'-binaphthyl to propeller chirality of the trivalent boron center can be realized when a Me2 N and a Mes2 B group (Mes=mesityl) are introduced at the 2,2'-positions of the 1,1'-binaphthyl skeleton (BN-BNaph) owing to the strong π-π interaction between the Me2 N-bonded naphthyl ring and the phenyl ring of one adjacent Mes group, which not only exerts great steric hindrance on the rotation of the two Mes groups but also gives unequal stability to the two configurations of the boron center for a given configuration of the binaphthyl moiety. The stereostructures of the boron center were fully characterized through 1 H NMR spectroscopy, X-ray crystal analyses, and theoretical calculations. Detailed comparisons with the analog BN-Ph-BNaph, in which the Mes2 B group is separated from 1,1'-binaphthyl by a para-phenylene spacer, confirmed the essential role of π-π interaction for the successful chirality relay in BN-BNaph.

Development of an axially chiral sp3P/sp3NH/sp2N-combined linear tridentate ligand—fac-selective formation of Ru(II) complexes and application to ketone hydrogenation

A newly developed chiral linear tridentate ligand, R-PN(H)N (R=H or Ph), possesses Ph2P and PyCH2NH groups at C(2) and C(2′) positions of the 1,1′-binaphthyl skeleton without or with a C(3)-Ph substituent. The steric effect of C(3)-Ph and the electronic effect of the DMSO co-ligand realize the facial selective generation of fac-RuCl2(Ph-PN(H)N)(dmso) and fac-[Ru(H-PN(H)N)(dmso)3](BF4)2, respectively. Both an H–Ru⋯sp3N–H reaction site responsible for the donor–acceptor bifunctional catalyst (DACat) and a fence/plane chiral context were constructed by means of the following advantageous points: i) the sp3P, sp3N, and sp2N ligating atoms have different electronic properties; ii) DMSO trans to sp3N strongly coordinates to Ru and is fixed by a PyC(6)H⋯OS hydrogen bond; and iii) the single NH function simplifies the DACat reaction site. The synergistic effect has led to success in the asymmetric hydrogenation of sterically demanding ketones. Structural characteristics of first-row transition metal complexes of R-PN(H)N have been also investigated.

ChemInform Abstract: Asymmetric Hydrosilylation of Styrene by Palladium Catalysts Coordinated with Chiral Phosphoramidite Ligands from 3,3′‐Disubstituted 1,1′‐Binaphthols.

Owing to its high catalytic activity, perfect regioselectivity, and an easy-manipulation without producing any byproduct, palladium-catalyzed asymmetric hydrosilylation of styrene has become a potent methodology to show their efficiencies of newly-developed chiral monodentate phosphorus ligands recently. Ever since a significant improvement for catalytic activity and enantioselectivity in the hydrosilylation of styrenes was achieved by chiral monophosphine (MOP) ligands based on the 2-diphenylphosphino-1,1'-binaphthyl skeleton, several monodentate phosphorus ligands, such as phosphoramidites, planar chiral monophosphines, and helically chiral phosphines have been applied to the hydrosilylation of styrenes to afford moderate to excellent enantioselectivities. Of those monodentate ligands, H-MOP derivative (R)-L1 lacking a substituent at the 2'-position of the binaphthyl and a phosphoramidite ligand (SA,RC,RC)-L2 3a derived from (S)-1,1'-binaphthol and bis((R)-1-phenylethyl)amine have been reported to be the most efficient ligands in the hydrosilylation of styrenes (Figure 1). In particular, chiral phosphoramidites have been paid much attention mainly due to their excellent catalytic activities and stereoselectivities in various catalytic reactions and easy accessibility from readily available diols and amines nowadays. On continuous efforts to expand the substrate scope of the hydrosilylation with various ligands, we are interested in the modifications of phosphoramidite ligands based on the 1,1'-binaphthol to evaluate substituent effects on enantioselectivity in the hydrosilylation. Here we wish to report a palladium-catalyzed asymmetric hydrosilylation of styrene (1) with trichlorosilane using chiral phosphoramidites L3 derived from (S)-3,3'-disubstituted 1,1'-binaphthols and secondary amines. In the hydrosilylation of styrene, 1-phenyl-1-(trichlorosilyl)ethane (2) was obtained in high yield and the benzylic silane 2 was transformed to optically active 1-phenylethanol (3) by a stereospecific oxidative cleavage of the C-Si bond with retention of configuration (Scheme 1). Chiral ligands L3 were prepared from (S)-1,1'-binaphthols having diphenyl or dimethyl groups at 3,3'-positions of the binaphthyl according to the known procedure. The hydrosilylation was carried out without solvent in the presence of 1.0 mol % of palladium catalysts generated in situ by mixing [PdCl(πC3H5)]2 and L3 (Pd/P = 1/2). The reactions were completed 20 C within 20 h to give 2, whose enantioselectivities were determined after the stereospecific oxidation into 3. The catalytic activity with the ligands L3 was high enough with all the ligands except for L3a and L3d, however, the enantioselectivities varied according to the ligands as shown in Table 1. The enantioselectivities were strongly dependent on the substituents at 3,3'-positions of the binaphthyl in the ligands. It was found that the ligands having diphenyl groups induced the higher enantioselectivities. Thus, the phosphoramidites from 3,3'-diphenylbinaphthol showed the higher

Investigation of the interaction between a novel unnatural chiral ligand and reactant on palladium for asymmetric hydrogenation.

We report about the mechanistic studies of the reaction between a newly synthesized (S)-2-((R)-3H-dinaphtho[2,1-c:1',2'-e]azepin-4(5H)-yl)-2-phenylethanol based on the binaphthyl skeleton and (E)-2-methyl-5-phenylpent-2-enoic acid for the asymmetric hydrogenation of α,β-unsaturated acids with heterogeneous palladium catalysts. The specific interactions between the chiral ligand and reactant were investigated in solution with palladium nanoparticles, as well as under ultrahigh vacuum (UHV) conditions on the palladium metal surface in the absence of hydrogen. The reactions were explored using nuclear magnetic resonance (NMR) spectroscopy, scanning tunneling microscopy (STM), and high-resolution photoemission spectroscopy (HRPES) combined with density functional theory (DFT) calculations. A NMR study identified the interaction between both molecules with palladium nanoparticles in solution. In addition, STM and HRPES studies revealed the spatial distribution and configuration of both compounds on the palladium metal surface under UHV conditions. The theoretical results support the experimental results with respect to the interaction energy value. It was found that the reaction between the ligand and reactant occurs with hydrogen bonding on palladium surface, simultaneously. The present study provides mechanistic details of the asymmetric hydrogenation reaction, which bears a correlation between the ligand, reactant, and catalyst during the reaction.

Asymmetric Hydrosilylation of Styrene by Palladium Catalysts Coordinated with Chiral Phosphoramidite Ligands from 3,3'-Disubstituted 1,1'-Binaphthols

Owing to its high catalytic activity, perfect regioselectivity, and an easy-manipulation without producing any byproduct, palladium-catalyzed asymmetric hydrosilylation of styrene has become a potent methodology to show their efficiencies of newly-developed chiral monodentate phosphorus ligands recently. Ever since a significant improvement for catalytic activity and enantioselectivity in the hydrosilylation of styrenes was achieved by chiral monophosphine (MOP) ligands based on the 2-diphenylphosphino-1,1'-binaphthyl skeleton, several monodentate phosphorus ligands, such as phosphoramidites, planar chiral monophosphines, and helically chiral phosphines have been applied to the hydrosilylation of styrenes to afford moderate to excellent enantioselectivities. Of those monodentate ligands, H-MOP derivative (R)-L1 lacking a substituent at the 2'-position of the binaphthyl and a phosphoramidite ligand (SA,RC,RC)-L2 3a derived from (S)-1,1'-binaphthol and bis((R)-1-phenylethyl)amine have been reported to be the most efficient ligands in the hydrosilylation of styrenes (Figure 1). In particular, chiral phosphoramidites have been paid much attention mainly due to their excellent catalytic activities and stereoselectivities in various catalytic reactions and easy accessibility from readily available diols and amines nowadays. On continuous efforts to expand the substrate scope of the hydrosilylation with various ligands, we are interested in the modifications of phosphoramidite ligands based on the 1,1'-binaphthol to evaluate substituent effects on enantioselectivity in the hydrosilylation. Here we wish to report a palladium-catalyzed asymmetric hydrosilylation of styrene (1) with trichlorosilane using chiral phosphoramidites L3 derived from (S)-3,3'-disubstituted 1,1'-binaphthols and secondary amines. In the hydrosilylation of styrene, 1-phenyl-1-(trichlorosilyl)ethane (2) was obtained in high yield and the benzylic silane 2 was transformed to optically active 1-phenylethanol (3) by a stereospecific oxidative cleavage of the C-Si bond with retention of configuration (Scheme 1). Chiral ligands L3 were prepared from (S)-1,1'-binaphthols having diphenyl or dimethyl groups at 3,3'-positions of the binaphthyl according to the known procedure. The hydrosilylation was carried out without solvent in the presence of 1.0 mol % of palladium catalysts generated in situ by mixing [PdCl(πC3H5)]2 and L3 (Pd/P = 1/2). The reactions were completed 20 C within 20 h to give 2, whose enantioselectivities were determined after the stereospecific oxidation into 3. The catalytic activity with the ligands L3 was high enough with all the ligands except for L3a and L3d, however, the enantioselectivities varied according to the ligands as shown in Table 1. The enantioselectivities were strongly dependent on the substituents at 3,3'-positions of the binaphthyl in the ligands. It was found that the ligands having diphenyl groups induced the higher enantioselectivities. Thus, the phosphoramidites from 3,3'-diphenylbinaphthol showed the higher

Biaryl-based anion receptors bearing thiourea groups: fluoride anion receptor

The synthesis, characterization and binding studies with anions for biaryl-based anion receptors bearing thiourea groups have been described. The results revealed that receptors (1 and 2) showed good selectivity and binding affinity for F−, and among them binaphthyl-based receptor (1a) showed the best binding affinity for F− in comparison to other tested anions (Cl−, Br−, I−, \( {\text{NO}}_{3}^{ - } ,\;{\text{HSO}}_{4}^{ - } , \) AcO− and \( {\text{H}}_{2} {\text{PO}}_{4}^{ - } \)). This is probably due to the fact that the moderate rigidity of binaphthyl skeleton in 1a is able to provide the better geometry of two thiourea groups for incorporating F− into the binding pocket. The higher basicity of F− also participated in this selectivity.

A Selective, Sensitive, and Chromogenic Chemodosimeter for Cyanide Based on the 1,1′-Binaphthyl Scaffold

A highly selective chemodosimeter 1 for cyanide based on the 1,1'-binaphthyl skeleton is described which demonstrated significant visual change and a low limit of detection. Interestingly, a reversible process triggered successively by CN(-) and Au(3+) is also observed and determined by fluorescence, UV-vis spectra, (1)H NMR titration, and ESI-MS.

ChemInform Abstract: Synthesis of 3,3′‐Diaryl‐Substituted 2,2′‐Diamino‐1,1′‐binaphthyl and Its Derivatives.

AbstractEach step affords the product with &lt; 90% yield.

The artificial binaphthyl amino acid 6-amino-6′-carboxyethyl-2-methoxy-2′-hydroxy-1,1′-binaphthyl (Bna): synthesis and assembly of Bna peptides

The new binaphthyl-based amino acid 6-amino-6′-carboxyethyl-2-methoxy-2′-hydroxy-1,1′-binaphthyl (Bna) is presented, which combines the axially chiral binaphthyl core, a phenolic OH-group as well as terminating amino and carboxyl groups in one structure. The large aromatic rings of the compound provide molecular spacing and π-surface attraction in assembled Bna oligoamides. The synthesis of Bna derivatives is reported, both with the ( R )- and with the ( S )-binaphthyl skeleton. Several dipeptides of ( R )- or ( S )-Bna units combined with natural amino acids, were prepared as ‘building blocks’ for the synthesis of extended Bna peptides. The tetrapeptide Boc-( S )-Val-( S )-Bna(OH)-( S )-Val-( S )-Bna(OPiv)- O - n -But ( 12 ) and the pentapeptide Boc-( S )-Val-( S )-Bna(OH)-( S )-Val-( S )-Bna(OH)-Gly-OH ( 13 ) were prepared via conventional solution phase synthesis and solid phase synthetic techniques, respectively. Compound 12 shows an interesting dynamic 1 H NMR spectrum suggesting compact and aggregated forms in dichloromethane. Compound 13 accelerates the enolisation of acetone. The use of more complex Bna peptides as organo catalysts is proposed.

ChemInform Abstract: Asymmetric trans-Addition Reactions Using Chiral Selenobinaphthyls

Abstract Asymmetric trans-addition reactions of (E)-phenylpropene, a mechanistically novel reactions, have been achieved by using chiral selenium-containing binaphthyl derivatives. Introduction of an amide group at 2′-position in the binaphthyl skeleton enhances considerably the diastereomeric excess (d.e.) of the asymmetric reaction presumably due to attractive interaction between the nitrogen lone pair and the seleniranium intermediate. Introduction of another chiral center in the amide group further enhances the d.e. as high as 79 %, which is the highest asymmetric induction ever achieved in the asymmetric trans-addition reaction.

Insights into the Origins of Configurational Stability of Axially Chiral Biaryl Amines with an Intramolecular N−H−N Hydrogen Bond

Configurationally stable chiral biaryl amines with an intramolecular N-H-N hydrogen bond have been developed. The barriers for racemization are in the range of 19.3-28.2 kcal/mol, which corresponds to the half-lives of racemization of the enantiomers in the range of 7 s to 2 years at 20 degrees C. Enantiomers of some of these compounds were separable by HPLC with chiral stationary phases. The biaryl amines are supposed to have a conformation similar to that of a binaphthyl skeleton, which was indicated by an X-ray crystal analysis of a biaryl amine. The N-H appears at 11.1-13.3 ppm in their (1)H NMR spectrum in CDCl(3), indicating strong hydrogen bonding. Biaryl amines with an extremely strong intramolecular N-H-N hydrogen bond (delta(NH) approximately 13 ppm) were assumed to undergo racemization without cleavage of an N-H-N hydrogen bond, while those with a mediumly strong N-H-N hydrogen bond (delta(NH) approximately 11 ppm) are assumed to undergo racemization via cleavage of an N-H-N hydrogen bond. Hydrogen/deuterium exchange of a chiral biaryl amine was found to proceed without any trace of racemization.

Synthesis of 3,3′-Diaryl-Substituted 2,2′-Diamino-1,1′-binaphthyl and Its Derivatives

Substitution at the 3 and/or 3' position of a binaphthyl skeleton sometimes enhances stereoselectivity during asymmetric reactions. High-yield and stepwise introduction of aryl groups into the 2,2'-diamino derivative has been established for the first time via an ortho-lithiation/iodization/Suzuki-Miyaura coupling protocol. The results described herein will facilitate the synthesis of a variety of 3,3'-substituted 2,2'-diamino-1,1'-binaphthyl compounds, which are key intermediates for obtaining valuable related ligands and organocatalysts.

Comparison of HPLC enantioseparation of substituted binaphthyls on CD‐, polysaccharide‐ and synthetic polymer‐based chiral stationary phases

Retention and enantioseparation behavior of ten 2,2'-disubstituted or 2,3,2'-trisubstituted 1,1'-binaphthyls and 8,3'-disubstituted 1,2'-binaphthyls, which are used as catalysts in asymmetric synthesis, was investigated on eight chiral stationary phases (CSPs) based on beta-CD, polysaccharides (tris(3,5-dimethylphenylcarbamate) cellulose or amylose CSPs) and new synthetic polymers (trans-1,2-diamino-cyclohexane, trans-1,2-diphenylethylenediamine and trans-9,10-dihydro-9,10-ethanoanthracene-(11S,12S)-11,12-dicarboxylic acid CSPs). Normal-, reversed-phase and polar-organic separation modes were employed. The effect of the mobile phase composition was examined. The enantiomeric separation of binaphthyl derivatives, which possess quite similar structures, was possible in different enantioselective environments. The substituents and their positions on the binaphthyl skeleton affect their properties and, as a consequence, the separation system suitable for their enantioseparation. In general, the presence of ionizable groups on the binaphthyl skeleton, substitution with non-identical groups and a chiral axis in the 1,2' position had the greatest impact on the enantiomeric discrimination. The 8,3'-disubstituted 1,2'-binaphthyl derivatives were the most easily separated compounds in several separation systems. From all the chiral stationary phases tested, cellulose-based columns were shown to be the most convenient for enantioseparation of the studied analytes. However, the polymeric CSPs with their complementary behavior provided good enantioselective environments for some derivatives that could be hardly separated in any other chromatographic system.

Development of Dinuclear Vanadium Catalysts for Enantioselective Coupling of 2-Naphthols via a Dual Activation Mechanism

This review describes our recent efforts in the development of chiral dinuclear vanadium complexes which work as dual activation catalysts for oxidative coupling of 2-naphthols. A chiral dinuclear vanadium(IV) complex (R(a),S,S)-1a possessing (S)-tert-leucine moieties at the 3,3'-positions of the (R)-binaphthyl skeleton was developed, and found to promote oxidative coupling of 2-naphthol to afford (S)-1,1'-bi-2-naphthol (BINOL) with 91% ee. To verify the dual activation mechanism, mononuclear vanadium(IV) complex (S)-10 was also prepared. Kinetic analysis revealed that the reaction rate of oxidative coupling of 2-naphthol promoted by (R(a),S,S)-1a is 48.3 times faster than that of (S)-10. In the coupling reaction, the two vanadium metals in the chiral complex activate two molecules of 2-naphthol simultaneously achieving a high reaction rate with high enantiocontrol. Since the dinuclear vanadium(IV) complex was found to be readily oxidized to afford a corresponding vanadium(V) species during preparation in air, a new synthetic procedure using VOCl3 and a convenient one-pot procedure using VOSO4 under O2 have been applied towards dinuclear vanadium(V) complexes (R(a),S,S)-2. The coupling of 2-naphthol was catalyzed by (R(a),S,S)-2 with reaction rates enhanced 2.3 times faster than that of (R(a),S,S)-1a, which is likely a precatalyst. To the best of our knowledge, (R(a),S,S)-1a, 2, and 3 show considerably higher catalytic activity than previously reported vanadium complexes for oxidative coupling of 2-naphthols.