Detection of chiral perturbations in ferroelectric liquid crystals induced by an atropisomeric biphenyl dopant

The atropisomeric dopant 2,2',6,6'-tetramethyl-3,3'-dinitro-4,4'-bis[(4-nonyloxybenzoyl)oxy]biphenyl (1) induces a ferroelectric SmC phase when doped into the SmC liquid crystal hosts 2-(4-butyloxyphenyl)-5-octyloxypyrimidine (PhP1) and (+/-)-4-[(4-methylhexyl)oxy]phenyl 4-decyloxybenzoate (PhB). The propensity of dopant 1 to induce a spontaneous polarization (polarization power) is much higher in PhP1 than in PhB (1555 nC/cm(2) vs <35 nC/cm(2)), which is attributed to a greater propensity of 1 to undergo chirality transfer via core-core interactions with PhP1. In previous work, we postulated that a chiral perturbation exerted by 1 in PhP1 amplifies the polarization power of the dopant by causing a chiral distortion of the mean field potential (binding site) constraining the dopant in the SmC host, as described by the Chirality Transfer Feedback (CTF) model. To test the validity of the CTF model, and to provide a more direct assessment of the chiral perturbation exerted by dopant 1 on surrounding host molecules, we measured the effect of 1 on the polarization power of other chiral dopants acting as probes. In one series of experiments, (S,S)-5-(2,3-difluorooctyl)-2-(4-octylphenyl)pyridine (MDW950) and (S)-4-(1-methylheptyloxy)phenyl 4-decyloxybenzoate (4), which mimic the structures of PhP1 and PhB, were used as probes. In another series of experiments, the atropisomeric dopant 2,2',3,3',6,6'-hexamethyl-4,4'-bis[(4-nonyloxybenzoyl)oxy]biphenyl (2) was used as probe in PhP1. The results of the probe experiments suggest that dopant 1 exerts a much stronger chiral perturbation in PhP1 than in PhB. More significantly, the results of experiments using 2 as probe show that the chiral perturbation exerted by 1 can amplify the polarization power of another atropisomeric dopant, thus providing the first experimental evidence of the CTF effect.     

Ferroelectric liquid crystals induced by dopants with axially chiral 2,2'-spirobiindan-1,1'-dione cores: diether vs. diester side-chains

A series of axially chiral 5,5'- and 6,6'-dialkanoyloxy-2,2'-spirobiindan-1,1'-dione dopants, (R)-2 and (R)-4a-4c were synthesized in optically pure form and their ferroelectric polarization powers, δ_p, measured in four liquid crystal hosts with isotropic (I)-nematic (N)-smectic A (SmA)-smectic C (SmC) phase sequences. The results show that the sign of polarization P _S induced by (R)-2 and (R)-4a-4c follows the same trend as that previously reported for the 5,5'- and 6,6'-diheptyloxy-2,2'-spirobiindan-1,1'-dione dopants, (R)-1 and (R)-3. The polarization induced by (R)-2 in the host DFT is below detection limits, and the sign of P _S was found to invert as a function of temperature at mole fractions as low as 0.01. On the other hand, the polarization power of the 6,6'-diheptanoyloxy dopant (R)-4b in the host NCB76 is -1449 nC cm^-2, the fourth highest value reported so far, and more than three times the δ_p value of the 5,5'-diheptanoyloxy analogue (R)-2 in that host (+474 nC cm^-2). Results of ²H NMR experiments suggest that (R)-4b exerts stronger local perturbations in NCB76 than (R)-2, and that these perturbations may be chiral in nature.     

Ferroelectric liquid crystals induced by atropisomeric biphenyl dopants: the effect of chiral perturbations on achiral dopants

The addition of the achiral biphenyl dopant 2,2',6,6'-tetramethyl-4,4'-bis(4-n-nonyloxybenzoyloxy)biphenyl (3) or its dithionoester or dithioester analogue (4, 5) to a 4 mol % mixture of the atropisomeric biphenyl dopant (R)-2,2',6,6'-tetramethyl-3,3'-dinitro-4,4'-bis(4-n-nonyloxybenzoyloxy)biphenyl, (R)-1, in the phenylpyrimidine SmC host PhP1 produces a significant amplification of the spontaneous polarization induced by (R)-1. This amplification may be due to a chiral perturbation by (R)-1 which causes a shift in the equilibrium between enantiomeric conformations of the achiral dopant. The degree of polarization amplification afforded by the achiral dopant, as expressed by the polarization amplification factor PAF, varies with the nature of the linking group. This may be ascribed to different rotational distributions of the core transverse dipole moments relative to the polar axis of the SmC* phase and/or to differences in lateral bulk of the polar linking groups. The latter may affect the degree of chiral molecular recognition achieved by 3-5 in the binding site of the SmC* phase.     

Bidirectional racemic synthesis of the biologically active quinone cardinalin 3

Readily available 2,2',6,6'-tetramethoxy-1,1'-biphenyl was transformed in 14 synthetic steps into the natural product cardinalin 3 using a bidirectional approach. One of the key steps was the formation of the cis-1,3-dimethylnaphtho[2,3-c]pyran ring. (+/-)-1,1'-[6,6'-Diallyl-5,5'-bis(benzyloxy)-1,1',3,3'-tetramethoxy-2,2'-binaphthalene-7,7'-diyl]diethanol was treated with O(2) in the presence of CuCl(2) and catalytic PdCl(2) to afford 5,5'-bis(benzyloxy)-7,7',9,9'-tetramethoxy-1,1',3,3'-tetramethyl-1H,1'H-8,8'-bibenzo[g]isochromene. Hydrogenation of this compound afforded 7,7',9,9'-tetramethoxy-cis-1,3-cis-1',3'-tetramethyl-3,3',4,4'-tetrahydro-1H,1'H-8,8'-bibenzo[g]isochromene-5,5'-diol in quantitative yield, which was converted in 3 steps to cardinalin 3.     

Synthesis and catalytic activity of group 5 metal amides with chiral biaryldiamine-based ligands

A new series of group 5 metal amides have been prepared from the reaction between V(NMe(2))(4) or M(NMe(2))(5) (M = Nb, Ta) and chiral ligands, (R)-2,2'-bis(mesitoylamino)-1,1'-binaphthyl (1H(2)), (R)-5,5',6,6',7,7',8,8'-octahydro-2,2'-bis(mesitoylamino)-1,1'-binaphthyl (2H(2)), (R)-6,6'-dimethyl-2,2'-bis(mesitoylamino)-1,1'-biphenyl (3H(2)), (R)-2,2'-bis(mesitylenesulfonylamino)-6,6'-dimethyl-1,1'-biphenyl (4H(2)), (R)-2,2'-bis(diphenylthiophosphoramino)-1,1'-binaphthyl (5H(2)), (R)-2,2'-bis[(3-tert-butyl-2-hydroxybenzylidene)amino]-6,6'-dimethyl-1,1'-biphenyl (6H(2)), (R)-2,2'-bis[(3,5-di-tert-butyl-2-hydroxybenzylidene)amino]-6,6'-dimethyl-1,1'-biphenyl (7H(2)), (R)-2,2'-bis[(3-tert-butyl-2-hydroxybenzylidene)amino]-1,1'-binaphthyl (8H(2)), (S)-2-(mesitoylamino)-2'-(dimethylamino)-1,1'-binaphthyl (9H), and (R)-2-(mesitoylamino)-2'-(dimethylamino)-6,6'-dimethyl-1,1'-biphenyl (10H), which are derived from (R) or (S)-2,2'-diamino-1,1'-binaphthyl, and (R)-2,2'-diamino-6,6'-dimethyl-1,1'-biphenyl, respectively. Treatment of V(NMe(2))(4) or M(NMe(2))(5) (M = Nb, Ta) with 1 equiv of C(2)-symmetric amidate ligands 1H(2), 2H(2), 3H(2), 4H(2), and 5H(2), or Schiff base ligands 6H(2), 7H(2) and 8H(2) at room temperature gives, after recrystallization from a benzene, toluene or n-hexane solution, the vanadium amides (1)V(NMe(2))(2) (11), (2)V(NMe(2))(2) (14), (3)V(NMe(2))(2) (17), (5)V(NMe(2))(2) (22), (6)V(NMe(2))(2) (23) and (7)V(NMe(2))(2) (24), and niobium amides (1)Nb(NMe(2))(3) (12), (2)Nb(NMe(2))(3) (15), (3)Nb(NMe(2))(3) (18), (4)Nb(NMe(2))(3) (20) and [2-(3-Me(3)C-2-O-C(6)H(3)CHN)-2'-(N)-C(20)H(12)][2-(Me(2)N)(2)CH-6-CMe(3)-C(6)H(3)O]NbNMe(2)·C(7)H(8) (25·C(7)H(8)), and tantalum amides (1)Ta(NMe(2))(3) (13), (2)Ta(NMe(2))(3) (16), (3)Ta(NMe(2))(3) (19) and (4)Ta(NMe(2))(3) (21) respectively, in good yields. Reaction of V(NMe(2))(4) or M(NMe(2))(5) (M = Nb, Ta) with 2 equiv of C(1)-symmetric amidate ligands 9H or 10H at room temperature gives, after recrystallization from a toluene or n-hexane solution, the chiral bis-ligated vanadium amides (9)(2)V(NMe(2))(2)·3C(7)H(8) (27·3C(7)H(8)) and (10)V(NMe(2))(2) (28), and chiral bis-ligated metallaaziridine complexes (10)(2)M(NMe(2))(η(2)-CH(2)NMe) (M = Nb (29), Ta (30)) respectively, in good yields. The niobium and tantalum amidate complexes are stable in a toluene solution at or below 160 °C, while the vanadium amidate complexes degrade via diemthylamino group elimination at this temperature. For example, heating the complex (2)V(NMe(2))(2) (14) in toluene at 160 °C for four days leads to the isolation of the complex [(2)V](2)(μ-NMe(2))(2) (26) in 58% yield. These new complexes have been characterized by various spectroscopic techniques, and elemental analyses. The solid-state structures of complexes 12, 13, and 15-30 have further been confirmed by X-ray diffraction analyses. The vanadium amides are active chiral catalysts for the asymmetric hydroamination/cyclization of aminoalkenes, affording cyclic amines in moderate to good yields with good ee values (up to 80%), and the tantalum amides are outstanding chiral catalysts for the hydroaminoalkylation, giving chiral secondary amines in good yields with excellent ee values (up to 93%).     

Ferroelectric liquid crystal dopants with a chiral (R,R)-2,3-difluorooctyloxy side-chain: host dependence of the polarization power

The polarization powers δ_p of four chiral dopants with (R,R)-2,3-difluorooctyloxy side-chains were measured in four liquid crystal hosts with isotropic (I)-nematic (N)-smectic A (SmA)-smectic C (SmC) phase sequences. The four chiral dopants differ in terms of their core structures: 2-phenylpyridine (MDW950), biphenyl (5), 2-phenylpyrimidine (6) and 2-(3-nitrophenyl)pyrimidine (7). In each case, δ_p varies with the structure of the liquid crystal host, which is consistent with the behaviour of so-called Type II dopants that normally feature a chiral core structure. The δ_p(host) profile was found to depend on the degree of biaxiality of the dopant core structure, and on the degree of steric coupling between the chiral 2,3-difluorooctyloxy side-chain and the core. Conformational analyses at the B3LYP/6-31G* level suggest that the 2,3-difluorooctyloxy side-chain is conformationally more rigid than conventional chiral side-chains due to the added electrostatic repulsion of the two adjacent fluoro groups combined with the hyperconjugative 'gauche effect', and may therefore have a higher degree of biaxiality on the time average. This biaxial character should make the chiral side-chain more sensitive to variations in quadrupolar ordering imposed by the SmC phase of the liquid crystal host, and may therefore explain the dependence of δ_p on the host structure reported herein.     

Asymmetric Morita-Baylis-Hillman reaction of arylaldehydes with 2-cyclohexen-1-one catalyzed by chiral bis(thio)urea and DABCO

Novel bis(thio)urea organocatalysts were synthesized from axially chiral (R)-(-)-5,5',6,6',7,7',8,8'-octahydro-1,1'-binaphthyl-2,2'-diamine (H8-BINAM), and their catalytic abilities have been examined in the Morita-Baylis-Hillman reaction of 2-cyclohexen-1-one or 2-cyclopenten-1-one with a wide range of aromatic aldehydes in combination with DABCO. The best result was achieved in the reaction of 3-fluorobenzaldehyde with 2-cyclohexen-1-one to give the desired Morita-Baylis-Hillman product in 79% yield and 88% ee.     

Rhodium-catalyzed linear cross-trimerization of two different alkynes with an alkene and two different alkenes with an alkyne

Crossing paths with rhodium: A cationic Rh(I)/H(8)-BINAP complex has been found to catalyze the linear cross-trimerization of terminal alkynes, acetylenedicarboxylates, and acrylamides to give substituted trienes. The asymmetric linear cross-trimerization, giving substituted chiral dienes, has also been achieved by using monosubstituted alkenes and (R)-BINAP instead of terminal alkynes and H(8)-BINAP (see scheme; H(8)-BINAP = 2,2'-bis(diphenylphosphino)-5,5',6,6',7,7',8,8'-octahydro-1,1'-binaphthyl; BINAP = 2,2'-bis(diphenylphosphino)-1,1'-binaphthyl]).     

Photoinduced polarization inversion in a ferroelectric liquid crystal using an ambidextrous chiral thioindigo dopant

In this Communication, we report the first example of photoswitching of a ferroelectric SmC* liquid crystal based on a photoinduced sign inversion of the spontaneous polarization (PS) induced by a single chiral dopant. This is achieved without concomitant destabilization of the SmC* phase using the "ambidextrous" dopant 6-((R,R)-2,3-difluorooct-1-yloxy)-5'-nitro-6'-((R)-2-octyloxy)thioindigo. The (R)-2-octyloxy side chain is sterically coupled to the thioindigo core via the nitro substituent and induces a positive polarization, whereas the (R,R)-2,3-difluorooct-1-yloxy side chain is decoupled from the core and induces a negative polarization. With this new design, the increase in transverse dipole moment of the thioindigo core upon trans-cis photoisomerization raises the polarization power of the coupled 2-octyloxy/thioindigo unit above that of the 2,3-difluorooctyloxy unit and inverts the net sign of PS.     

5,6-dihydroxyindole tetramers with "anomalous" interunit bonding patterns by oxidative coupling of 5,5',6,6'-tetrahydroxy-2,7'-biindolyl: emerging complexities on the way toward an improved model of eumelanin buildup

Chemical or enzymatic oxidation of 5,6-dihydroxyindole (1) leads to the rapid deposition of a black solid resembling eumelanin pigments by way of a complex oligomerization/polymerization process that proceeds in the early stages via dimers 2-3 and trimers 5-6 characterized by 2,4'- and 2,7'-couplings. Despite extensive efforts, the structures of the higher oligomers, which define the structural architecture and physicochemical properties of the eumelanin particles, have so far defied elucidation. Using a dimer-dimer coupling strategy that has recently allowed the first successful entry to a tetramer of 1, we report now three additional tetramers obtained by oxidation of 5,5',6,6'-tetrahydroxy-2,7'-biindolyl (3) with the peroxidase/H2O2 system. On the basis of extensive 2D NMR and mass spectrometric analysis, the products were identified as 5,5',5',5',6,6',6',6'-octaacetoxy-7,2':3',3':2',7'-tetraindolyl (acetylated 8, 3%), 5,5',5',5',6,6',6',6' '-octaacetoxy-2,7':4',4':7',2'-tetraindolyl (acetylated 9, 4%), and 5,5',5',5',6,6',6',6'-octaacetoxy-2,7':2',3':2',7'-tetraindolyl (acetylated 10, 5%), in which the inner units are linked through unexpected 3,3'-, 4,4'-, and 2,3'-linkages. If verified in further studies, the newly uncovered coupling patterns would entail important consequences for current models of eumelanin structure based on one-dimensional structural chains with extended pi-electron conjugation or pi-stacked flat oligomer aggregates.     

Synthesis and SmC* properties of chiral liquid crystalline terephthalates

Chiral ester derivatives of terephthalic acid containing one, three, or five phenyl rings were prepared by using (S)-2-methylbutanol or (R)-2-chloropropanol as starting materials. The one-ring terephthalates did not exhibit any liquid crystalline phases, but one of them was used as a chiral dopant in ferroelectric mixtures. Elongation of the aromatic core structure to three and five phenyl rings stabilized the SmA phase, whereas a (monotropic) SmC* phase was detected in some three-ring and five-ring derivatives. In ferroelectric mixtures based on the terephthalates, spontaneous polarizations up to 340 nC cm2 were measured.     

Ferroelectric liquid crystals induced by dopants with axially chiral 2,2′‐spirobiindan‐1,1′‐dione cores: diether vs. diester side‐chains

A series of axially chiral 5,5′‐ and 6,6′‐dialkanoyloxy‐2,2′‐spirobiindan‐1,1′‐dione dopants, (R)‐2 and (R)‐4a–4c were synthesized in optically pure form and their ferroelectric polarization powers, δ_p, measured in four liquid crystal hosts with isotropic (I)–nematic (N)–smectic A (SmA)–smectic C (SmC) phase sequences. The results show that the sign of polarization P _S induced by (R)‐2 and (R)‐4a–4c follows the same trend as that previously reported for the 5,5′‐ and 6,6′‐diheptyloxy‐2,2′‐spirobiindan‐1,1′‐dione dopants, (R)‐1 and (R)‐3. The polarization induced by (R)‐2 in the host DFT is below detection limits, and the sign of P _S was found to invert as a function of temperature at mole fractions as low as 0.01. On the other hand, the polarization power of the 6,6′‐diheptanoyloxy dopant (R)‐4b in the host NCB76 is ?1449 nC cm^?2, the fourth highest value reported so far, and more than three times the δ_p value of the 5,5′‐diheptanoyloxy analogue (R)‐2 in that host (+474 nC cm^?2). Results of ²H NMR experiments suggest that (R)‐4b exerts stronger local perturbations in NCB76 than (R)‐2, and that these perturbations may be chiral in nature.     

Convenient and efficient reduction of 1,1'-binaphthyls to H8-1,1'-binaphthyl derivatives with Pd and Ru catalysts on solid support

Hydrogenation of chiral 2,2'-functionalized 1,1'-binaphthyls with Pd and Ru solid-supported metal catalysts was found to be a clean and convenient pathway to 5,5',6,6',7,7',8,8'-octahydro-1,1'-dinaphthyl derivatives. In most cases no racemization was observed in the course of the reaction.     

Solubility of thioindigo dopants in a smectic liquid crystal host evaluated by 2H NMR spectroscopy

The solubility of two partially deuterated thioindigo dopants in a smectic liquid crystal host was evaluated by variable temperature ²H NMR spectroscopy and polarized microscopy. 2H NMR spectra showed that the dopant (±)-6,6'-bis(2-octyloxy)-5,5-dinitrothioindigo-d ₆ forms a homogeneous solution with the smectic phases of the liquid crystal host (±)-4-(4-methylhexyloxy)phenyl 4-decyloxybenzoate (PhB) up to its saturation point of 3 mol %. These results are consistent with polarized microscopy observations of the dopant crystallizing out of solution upon reaching a concentration of 3 mol %. On the other hand, ²H NMR spectra of (±)-5,5'-dichloro-6,6'-bis(2-octyloxy)thioindigo-d ₆ dissolved in PhB showed evidence of a partitioning of the solution between smectic and isotropic microdomains, which increases with increasing dopant concentration—from 1.2 to 9.1 mol %. To a large extent, this smectic/isotropic microphase separation could not be detected by polarized microscopy. These results suggest that ²H NMR spectroscopy can provide a more accurate determination of the occurrence and extent of microphase separation in doped liquid crystal samples.     

Synthesis and application of a new bisphosphite ligand collection for asymmetric hydroformylation of allyl cyanide

A series of mono- and bidentate phosphites was prepared with (S)-5,5',6,6'-tetramethyl-3,3'-di-tert-butyl-1,1'-biphenyl-2,2'-dioxy [(S)-BIPHEN] as a chiral auxiliary and screened in the asymmetric hydroformylation of allyl cyanide. These hydroformylation results were compared with those of two existing chiral ligands, Chiraphite and BINAPHOS, whose utility in asymmetric hydroformylation has been previously demonstrated. Bisphosphite 11 with a 2,2'-biphenol bridge was found to be the best overall ligand for asymmetric hydroformylation of allyl cyanide with up to 80% ee and regioselectivities (branch-to-linear ratio, b/l) of 20 with turnover frequency of 625 [h(-)(1)] at 35 degrees C. BINAPHOS gave enantioselectivities up to 77% ee when the reaction was conducted in either acetone or neat but with poor regioselectivity (b/l 2.8) and activities 7 times lower than that of 11. The product of allyl cyanide hydroformylation using (R,R)-11 was subsequently transformed into (R)-2-methyl-4-aminobutanol, a useful chiral building block. Single-crystal X-ray structures of (S,S)-11 and its rhodium complex 19 were determined.     

Trianionic organoborate triangles

The rigid, angular ligand 3,3,3',3'-tetramethyl-1,1'spirobisindane-5,5',6,6'-tetrol, LH4, in the form of its tetra-anion, L(4-), affords crystalline compounds containing the triangular macrocyclic boron derivative [B3L3](3-) with the counter cations, triethylammonium, imidazolium, tetraethylammonium, and protonated dabco (dabco = 1,4-diazabicyclo[2,2,2]octane). Within a triangular unit all three chiral L(4-) ligands have the same hand although the crystal does contain a racemic mixture of macrocycles. In all four compounds, one out of the three counter-cations per macrocycle is bound inside the macrocycle.     

Directed metalation route to ferroelectric liquid crystals with a chiral fluorenol core: the effect of restricted rotation on polar order

A new series of smectic C* (SmC*) mesogens containing a chiral (R)-2-octyloxy side chain and either a fluorenone (2a-e) or chiral fluorenol (3a-e) core were synthesized using a combined directed ortho metalation-directed remote metalation strategy. The SmC phase formed by the fluorenol mesogens is more stable and has a wider temperature range than that formed by the fluorenone mesogens, which may be ascribed to intermolecular hydrogen bonding according to variable-temperature FT-IR measurements. The C11 fluorenol mesogens (R,R)-3d and (S,R)-3d were obtained in diastereomerically pure form and gave reduced polarization (Po) values of +106 and +183 nC/cm2, respectively, at 10 K below the SmA*-SmC* phase transition temperature. The difference in Po values suggests that the chiral fluorenol core contributes to the spontaneous polarization of the SmC* phase. This is ascribed to the bent shape of the fluorenol core, which should restrict its rotation with respect to the side chains in the SmC* phase and favor one orientation of its transverse dipole moment along the polar axis, and to steric coupling of the core to the chiral 2-octyloxy side chain.     

Synthesis of amidolanthanides with new chiral biaryl-based NNO ligands and their use as catalysts for enantioselective hydroamination/cyclization

A new series of amidolanthanides have been prepared from the reactions between Ln[N(SiMe3)2]3 and the chiral NNO ligands, (S)-2-(pyrrol-2-ylmethyleneamino)-2'-hydroxy-6,6'-dimethyl-1,1'-biphenyl (2H2) and (S)-5,5',6,6',7,7',8,8'-octahydro-2-(pyrrol-2-ylmethyleneamino)-2'-hydroxy-1,1'-binaphthyl (3H2), which are synthesized from the condensation of pyrrole-2-carboxaldehyde with 1 equiv of (S)-2-amino-2'-hydroxy-6,6'-dimethyl-1,1'-biphenyl or (S)-5,5',6,6',7,7',8,8'-octahydro-2-amino-2'-hydroxy-1,1'-binaphthyl, in the presence of molecular sieves at 70 degrees C, respectively. Treatment of 2H2 with 1 equiv of Ln[N(SiMe3)2]3 (Ln=Sm, Yb) in toluene under reflux, followed by recrystallization from a toluene solution, gives the dimeric amido complexes, {2-SmN(SiMe3)2}2.0.5C7H8 (6.0.5C7H8) and {2-YbN(SiMe3)2} 2.1.5C7H8(8.1.5C7H8), in good yields. While under similar reaction conditions, the reaction of 2H2 with 1 equiv of Y[N(SiMe3)2]3 leads to the isolation of a mixture of {2-YN(SiMe3)2}2 (7a) and {(2)2Y}Y[N(SiMe3)2]2(7b) in 82% total yield; the reaction of 3H2 with 1 equiv of Ln[N(SiMe3)2]3 (Ln=Y, Yb) gives the trinuclear complexes, {(3)2Ln}2LnN(SiMe3) 2.1.5C7H8 (Ln=Y(9.1.5C7H8), Yb(10.1.5C7H8)), in good yields. All compounds have been characterized by various spectroscopic techniques and elemental analyses. The solid-state structures of compounds 2H2 and 6- 10 have been further confirmed by X-ray diffraction analyses. Complexes 6- 9 are active catalysts for the asymmetric hydroamination/cyclization of aminoalkenes, affording cyclic amines in good yields with moderate ee values.     

Chiral nematic liquid crystals with helix inversion from (R)-1,1′-binaphthyl and cholesteryl ester moieties

In this study, on the concept of intramolecular chiral conflict between the (R)-1,1′-binaphthyl and cholesteryl ester moieties, we have designed and synthesised a new liquid crystal (LC) (R)-dicholesteryl 6,6′-[1,1′-binaphthyl-2,2′-diylbis(oxy)]dihexanoate [(R)-DC]. A helix inversion could be observed for the chiral nematic liquid crystal (N*-LC) comprising the commercial nematic LC (N-LC) host SLC1717 and (R)-DC on heating. As a comparison, (S)-dicholesteryl 6,6′-[1,1′-binaphthyl-2,2′-diylbis(oxy)]dihexanoate [(S)-DC] was also prepared. Due to the intramolecular chiral superposition between the (S)-1,1′-binaphthyl and cholesteryl ester moieties, the N*-LC comprising SLC1717 and (S)-DC also exhibited excellent temperature sensitivity.     

Chiral separation of 1,1'-bi-2-naphthol and its analogue on molecular imprinting monolithic columns by HPLC

Two molecular imprinting polymer (MIP) monolithic columns with (S)-(-)-1,1'-bi-2-naphthol and (R)-(+)-5,5',6,6',7,7',8,8'-octahydro-1,1'-bi-2-naphthol as the templating molecules, respectively, have been prepared by in situ polymerization using 4-vinylpyridine and ethylene dimethacrylate as functional monomer and cross-linker, respectively. The columns with good flow-through properties were obtained by changing the molar ratio of the functional monomer and the template molecule. The effects of mobile-phase composition on separation of enantiomers were systematically investigated. The results indicate that hydrophobic interaction in aqueous solution and hydrogen-bonding interaction in ACN between the enantiomers and polymers could play important roles in the retention and resolution. The effects of chromatographic conditions, such as flow rate, column temperature, sample loading, on the enantioseparation were also studied. Further, these two MIP columns show a cross-reactivity.