Bi-2-naphthol Research Articles

Asymmetric Catalytic Carbon—Carbon Bond Formations in a Fluorous Biphasic System Based on Perfluoroalkyl‐BINOLs.

Abstract Optically active 1,1′-binaphthols (BINOLS) substituted at the 4,4′; 6,6′ and 4,4′,6,6′ positions with perfluoroalkyl groups have been synthesized. Asymmetric diethylzinc and triethyl aluminum addition to aryl aldehydes in a fluorous biphasic system catalyzed by these perfluoroalkyl-BINOL–titanium complexes have been accomplished with good enantiomeric excess obtained.

Assembled Catalysts of Titanium and Non‐Cross‐Linked Chiral Copolymers for an Enantioselective Carbonyl‐ene Reaction.

AbstractFor Abstract see ChemInform Abstract in Full Text.

Catalytic effects of metal(IV) phosphates on the oxidation of phenol and 2-naphthol

Tetravalent metal phosphates form highly insoluble inorganic polymers and act as catalysts in some oxidative reactions. In the present work, α-amorphous zirconium, tin, titanium, zirconium tungstate (acidic and basic form), crystalline vanadyl, fibrous crystalline cerium and pellicular zirconium phosphates, were prepared and evaluated as catalysts, for the hydroxylation of phenol and 2-naphthol by hydrogen peroxide, in acetic acid. Oxidation of phenol yielded hydroquinone, catechol, cis, cis-muconic and cis, trans-muconic acids, depending on the catalyst. All oxidations of 2-naphthol produced 4-(2-hydroxy-1-naphthyl)-1,2-naphthoquinone but reaction with crystalline vanadyl phosphate also resulted in the formation of 1,1′-bi(2-naphthol).

A new method for optical resolution of BINOL by molecular complexation with ( S)-5-oxopyrrolidine-2-carboxanilide

A new method for optical resolution of racemic 1,1′-bi-2-naphthol (BINOL) has been developed through molecular complexation with a cheap and readily accessible ( S)-5-oxopyrrolidine-2-carboxanilide, affording the enantioenriched BINOL in up to 70.4% ee and 73.6% yield. X-Ray structural analysis of a molecular crystal formed between ( R)-BINOL and ( S)-5-oxopyrrolidine-2-carboxanilide indicates that the hydrogen bonding interactions between the carbonyl groups of amides and the hydroxyl groups of ( R)-BINOL predominate in the molecular complex formation. The chiral features of the amide and the complementary molecular packing in the crystal lattice control the stereochemistry of the guest in the molecular crystal.

Asymmetric C[sbnd]C bond formation by the mixed oxidative coupling of 1,1′-bi-2-naphthyl esters

Asymmetric CC bond formation was effected by the oxidative coupling of two different ester enolates using (R)-(+)-1,1′-bi(2-naphthol) as a common tether which served to link together both ester moieties in an asymmetric environment. Reduction of the corresponding succinates afforded diastereomerically pure 2,3-disubstituted-1,4-butanediols.

Efficient synthesis of 6-mono-bromo-1,1′-bi-2-naphthol

Through mono-ester formation of 1,1′-bi-2-naphthol (BINOL) with pivaloyl chloride the selective mono-bromination was achieved cleanly on the other ring to afford 6-mono-bromo-1,1′-bi-2-naphthol in an efficient 86% yield.

N-Alkoxyacrylamides as Substrates for Enantioselective Diels−Alder Reactions

[reaction: see text] The use of N-alkoxyacrylamides as substrates for Lewis acid catalyzed Diels-Alder reactions has been examined. Enantioselectivities up to 92% ee have been achieved using very simple chiral Lewis acids prepared from triisobutylaluminum and 2,2-dimethyl-alpha,alpha,alpha',alpha'-tetra-1-naphthalenyl-TADDOL (1-NaphtTADDOL). The use of Yamamoto's Zn-BINOL, easily prepared from Et2Zn and 1,1'-bi-2-naphthol (BINOL), proved to be even more efficient, and enantioselectivities up to 96% ee were achieved.

Asymmetric catalytic carbon–carbon bond formations in a fluorous biphasic system based on perfluoroalkyl-BINOLs

Optically active 1,1′-binaphthols (BINOLS) substituted at the 4,4′; 6,6′ and 4,4′,6,6′ positions with perfluoroalkyl groups have been synthesized. Asymmetric diethylzinc and triethyl aluminum addition to aryl aldehydes in a fluorous biphasic system catalyzed by these perfluoroalkyl-BINOL–titanium complexes have been accomplished with good enantiomeric excess obtained.

Assembled catalysts of titanium and non-cross-linked chiral copolymers for an enantioselective carbonyl-ene reaction

New insoluble chiral catalysts were prepared from a self-assembly of Ti(O- i-Pr) 4 and non-cross-linked copolymers with ( R)-binaphthol (BINOL) pendant groups. In the presence of one of the chiral catalysts, an enantioselective carbonyl-ene reaction proceeded at room temperature to give an adduct in 85% yield with 88% ee. This insoluble assembled catalyst was easily prepared and reusable.

Development and application of enantioselective Lewis acid-Lewis base bifunctional catalyst

The design, synthesis, and application of a new bifunctional enantioselective catalyst containing both Lewis acidity and Lewis basicity are described. Recent developments of chiral quaternary stereocenter synthesis through catalytic enantioselective Reissert-type reaction and cyanosilylation of ketones forming the S-enantiomer are chiefly reviewed. The catalysts are composed of a Lewis acid metal (aluminum, titanium, or lanthanide) and a Lewis base (the oxygen atom of a phosphine oxide), of which positions are defined by 2,2'-binaphthol (BINOL) or a carbohydrate scaffold. Utilizing these catalysts, we have developed a variety of enantioselective cyanation reactions, such as cyanosilylation of aldehydes and ketones, Strecker-type reaction, and Reissert-type reaction. These reactions showed a broad substrate generality. Investigations toward the elucidation of the reaction mechanism, involving kinetic studies, comparison of the results by control catalysts, and absolute configurations of the products, revealed that these reactions are catalyzed by a dual activation of a substrate and trimethylsilyl cyanide (TMSCN) by the Lewis acid and the Lewis base of these catalysts. Catalytic enantioselective synthesis of several drug lead compounds, such as anti-cancer epothilones, potent N-methyl-D-aspartate (NMDA) receptor antagonists, phenytoin analogs, salsolinol carboxylic acid, and anti-cancer camptothecin was achieved, using these reactions as key steps.

Selective reduction of aldehydes via BINOL–Zr complex

An easily assembled catalyst from (±)-BINOL (1,1′-bi-naphthol) and Zr(O i Pr) 4· i PrOH selectively reduces aldehydes at room temperature. Ketones remain intact under these conditions. A catalytic amount of BINOL–Zr complex in the presence of 2-propanol also effectively reduces a variety of chiral and achiral aldehydes.

Optically active BINOL core-based phenyleneethynylene dendrimers for the enantioselective fluorescent recognition of amino alcohols.

A dramatic enhancement in fluorescence intensity from 1,1'-bi-2-naphthol (BINOL) to dendritic phenyleneethynylenes containing the BINOL core was observed. The strong fluorescence of the dendrimers allows a very small amount of the chiral materials to be used for sensing. The light harvesting antennas of the dendrimer funnel energy to the center BINOL unit, whose hydroxyl groups upon interaction with a quencher molecule lead to fluorescence quenching. This mechanism makes the dendrimers have much more sensitive fluorescence responses than corresponding small molecule sensors. The fluorescence of these dendrimers can be enantioselectively quenched by chiral amino alcohols. It is observed that the fluorescence lifetime of the generation two dendrimer does not change in the presence of various concentrations of 2-amino-3-phenyl-1-propanol. This demonstrates that the fluorescence quenching is entirely due to static quenching. Thus, formation of nonfluorescent ground-state hydrogen-bond complexes between the dendrimers and amino alcohols is proposed to account for the fluorescent quenching. A linear relationship has been established between the Stern-Völmer constant of the generation two dendrimer and the enantiomeric composition of 2-amino-3-phenyl-1-propanol. Such enantioselective fluorescent sensors may allow a rapid determination of the enantiomeric composition of chiral molecules and are potentially useful in the combinatorial search of asymmetric catalysts and reagents.

New bidentate chiral phosphoramidites in copper-catalyzed asymmetric 1,4-addition of diethylzinc to cyclic α,β-enones: enantioselective tandem 1,4-addition-aldol reactions with 2-cyclopentenone

New bidentate phosphoramidites were prepared starting from α,α,α′,α′-tetraphenyl-2,2-dimethyl-1,3-dioxolane-4,5-dimethanol (TADDOL) or 1,1′-bi-2-naphthol (BINOL) and either 1,2-ethylene- or 1,3-propylenediamine N, N′-disubstituted with achiral or chiral groups. The use of these ligands in the copper-catalyzed enantioselective conjugate addition of diethylzinc to 2-cyclohexenone and 2-cyclopentenone afforded products with e.e.s of up to 89 and 83%, respectively.

Copper-Catalysed Asymmetric 1,4-Addition of Organozinc Compounds to Linear Aliphatic Enones Using 2,2′-Dihydroxy 3,3′-Dithioether Derivatives of 1,1′-Binaphthalene

Directed ortho dilithiation of bis(diethylcarbamate) or bis(MOM)-protected (Sa)-1,1′-bi(2-naphthol) followed by treatment with R2S2 [R = Me, Ph (X-ray structure)] or Me2Se2 cleanly affords the 3,3′ derivatives; the free naphthols are produced on deprotection. In the case of the bis(MOM) series, but not that of the bis(carbamates), some racemisation occurs. The ligand 2,2′-dihydroxy-3,3′-dimethylthio-1,1′-binaphthalene shows optimal performance in the addition of ZnEt2 to linear aliphatic enones (E)-R1C(O)CH=CHR2. Variation of the steric demands of R1 and R2 generates catalytic results consistent with binding of a zinc-based Lewis acid anti to the ene function and with the reactive conformation being s-cis. With enones containing the functions R2 = (CH2)nCH(OAlkyl)2 (n = 0−2), the ZnEt2 addition products undergo base-promoted cyclisation.

Asymmetric hydroformylation of styrene catalyzed by platinum complexes of chiral diphosphites with atropisomeric terminal moieties

To study the nature of steric and electronic effects of diphosphites, a novel diphosphite was synthesized and tested with regard of its catalytic performance in the hydroformylation of styrene catalyzed by platinum complexes. The novel ligand 3 was prepared by the reaction of enantiomerically pure pentane-2,4-diol with (S)-2-chloro-5,5',6,6',7,7',8,8'-octahydro-dinaphtho[2,1-d:1',2'-f][1,3,2]dioxaphosphepine based on H8-BINOL (H8-BINOL = 5,5',6,6',7,7',8,8'-octahydro-1,1'-bi-2-naphthol). For a comparative study, the BINOL (1,1'-bi-2-naphthol) based analogue 4 of 3 has also been synthesized. The highest chemoselectivity to aldehyde (71%) and regioselectivity to branched aldehyde (85%) with an enantiomer excess (ee) of 86% was obtained with the platinum(II)-SnCl2 catalytic system associated with (2S,4S)-bis(S)-3.Key words: asymmetric hydroformylation, chirality, homogeneous catalysis, P ligands, platinum.

Tetranuclear titanium 7,7'-modified binaphtholate cluster as a novel chiral Lewis acid catalyst.

Chiral tetranuclear Ti cluster, a cubic structure constituted of four Ti atoms and OHs, and six (R)-binaphthols (BINOL) bridged two Ti atoms as ligands, is shown to be a novel chiral Lewis acid catalyst for the [2+3] cycloaddition reaction with nitrones. The chiral Ti clusters with 7,7'-substituted (R)-BINOL ligands was synthesized to give enhanced enantiomeric excesses up to 78% ee.

Immobilization of BINOL by cross-linking copolymerization of styryl derivatives with styrene, and applications in enantioselective Ti and Al Lewis acid mediated additions of Et2Zn and Me3SiCN to aldehydes and of diphenyl nitrone to enol ethers

The chiral ligand 1,1'-bi-2-naphthol (BINOL) has been succesfully immobilized on polystyrene. Several dendritic and non-dendritic BINOL derivatives (3, and 13-17), bearing at least two polymerizable styryl groups, were prepared and fully characterized. Suspension copolymerization of the MOM- or TIPS-protected cross-linking BINOL ligands (MOM = methyloxymethyl, TIPS = triisopropylsilyl) with styrene, cleavage of the protecting-groups, and loading with a Lewis-acid afforded catalytically active polystyrene-supported BINOLates. The polymer-bound BINOLs p-3, and p-13-p-16 were tested in the Ti-BINOLate-mediated addition of Et2Zn to PhCHO. The enantioselectivities (up to 93%) and conversions obtained with the polymer-bound catalysts were in most cases identical (within experimental error) to those obtained with the unsubstituted 1,1'-bi-2-naphthol and with the non-polymerized BINOL cross-linkers under homogeneous conditions. Special focus was put on the reusability of the supported catalyst: the polymer-beads were used in up to 20 consecutive catalytic runs, with the best polymers showing no or only minor loss of selectivity. BINOL-polymers p-17, obtained by copolymerization of a 3,3'-distyryl-substituted BINOL 17a with styrene, were used in the BINOL. AlMe-mediated cycloaddition of diphenyl nitrone with alkyl vinyl ethers. In all cases the exo/endo selectivity (> or =92:8) and the enantioselectivities with which the exo-cycloadducts were formed (> or =95%) correspond to those observed in the homogeneous reactions. A dendritically cross-linked BINOL-polymer was also employed in the Ti-BINOLate-mediated cyanosilylation of pivalaldehyde. The enantiopurity of the cyanohydrine obtained in the first run was as high as in the homogeneous reaction (72%); surprisingly the catalytic performance of the supported catalyst increased steadily during the first catalytic cycles to reach 83%. Thus, cross-linking BINOLs can be succesfully incorporated into a polystyrene matrix (without racemization!) to give polymer-bound BINOL ligands that give excellent performance over many catalytic cycles with catalytic activities comparable with those of soluble analogues.

The Hexadecyltrimethylammonium Chloride Inclusion Complex with Rac-1,1′-Bi-2-Naphthol

The crystal structure of 1:1 inclusion complex of hexadecyltrimethylammonium chloride (16TAC) with rac-1,1′-bi-2-naphthol (BNP) [a = 47.968(2), b = 8.757(2), c = 18.249(2)Å, β = 100.772(6)°. C2/c, R = 0.075 for 2578 observed reflections] was determined by the X-ray diffraction method. In the crystal structure there is a strong hydrogen bond between one of the OH groups of BNP and the oxygen of water molecule (O1…OW, 2.665(3)Å). The chloride anion acts as the hydrogen acceptor of the OH group of the water molecule (OW…Cl-, 3.105(3)Å), and of the second OH group of BNP (O2…Cl-, 3.108(2)Å). The short C-H…C distances between hydrogen atoms of the alkyl carbon atom together with one of the methyl groups, and carbon atoms in one of the naphthol rings indicated an existence of C-H…π interactions. The hydrophobic long alkyl chain of the 16TAC molecule contributes to the unique molecular packing arrangement observed in the 16TAC/BNP complex. The alkyl chain of the 16TAC molecule in this crystal is bent at C10 and does not exhibit the complete zig-zag planes as reported on the 16TAC crystal. The BNP molecules are completely trapped between the 16TAC molecules, and the interdigitated arrangement of the 16TAC molecules are clearly observed in the ac-plane. The X-ray powder diffraction studies on the mixed powdered samples of 16TAC and BNP suggested that the complex can be obtained by crystallization from the solution and also by mixing powdered samples in a mortar.Racemic compound

Practical Method and Novel Mechanism for Optical Resolution of BINOL by Molecular Complexation with N-Benzylcinchoninium Chloride

A highly efficient and practical resolution of racemic 1,1′-bi-2-naphthol (BINOL) has been achieved through molecular complexation with N-benzylcinchoninium chloride, which can be readily prepared in 85% yield using an improved procedure through the reaction of cinchonine with benzyl chloride in dimethylformamide (DMF). It is found that the absolute configuration of BINOL included in the molecular crystals is R, which is the same as in the case of using N-benzylcinchonidinium chloride. This result is discussed in terms of molecular recognition in the solid state. X-Ray structural analysis of molecular crystal formed between ( R)-BINOL and N-benzylcinchoninium chloride indicates that the additive effect of the chiral features of the host, the interaction pattern between the functional groups of the host and guest, and the complementary molecular packing in the crystal lattice dominates the stereochemistry of the guest in the molecular crystal.

Lanthanide-catalyzed asymmetric 1,3-dipolar cycloaddition of nitrones to alkenes using 3,3′-bis(2-oxazolyl)-1,1′-bi-2-naphthol (BINOL-Box) ligands

New BINOL-derived ligands, 3,3′-bis(2-oxazolyl)-1,1′-bi-2-naphthols (BINOL-Box), bearing chiral bis-oxazoline at the 3,3′-carbons, were synthesized from commercially available 1,1′-bi-2-naphthol (BINOL). With the new ligands obtained, we found that asymmetric 1,3-dipolar cycloaddition reaction of N-benzylidenebenzylamine N-oxide ( 2) to 3-(( E)-2-butenoyl)-1,3-oxazolidin-2-one ( 1) was catalyzed by BINOL-Box–scandium complexes to give isoxazolidine 3 in high yield with high diastereo- and enantioselectivity. For example, the reaction of 1 with 2 catalyzed by a 6 mol% ( S, R)- 7d and 5 mol% Sc(OTf) 3 complex proceeded to give the endo-3 as the major diastereomer with an endo: exo ratio of 97:3 and 87% ee of the endo-product in the presence of 4 Å molecular sieves. Interestingly, the absolute configuration of the major product was changed according to the kind of additive used.