Cyclohexyl Group Research Articles

Flexibility of small molecular CD4 mimics as HIV entry inhibitors.

CD4 mimics such as YIR-821 and its derivatives are small molecules which inhibit the interaction between the Phe43 cavity of HIV-1 gp120 with host CD4, an interaction that is involved in the entry of HIV to cells. Known CD4 mimics generally possess three structural features, an aromatic ring, an oxalamide linker and a piperidine moiety. We have shown previously that introduction of a cyclohexyl group and a guanidine group into the piperidine moiety and a fluorine atom at the meta-position of the aromatic ring leads to a significant increase in the anti-HIV activity. In the current study, the effects of conformational flexibility were investigated by introduction of an indole-type group in the junction between the oxalamide linker and the aromatic moiety or by replacement of the oxalamide linker with a glycine linker. This led to the development of compounds with high anti-HIV activity, showing the importance of the junction region for the expression of high anti-HIV activity. The present data are expected to be useful in the future design of novel CD4 mimic molecules.

Steric control of supramolecular association in structures of Zn(S2COR)2withN,N′-bis(pyridin-4-ylmethyl)oxalamide

AbstractThe crystal and molecular structures of the one-dimensional coordination polymer [Zn(S2COEt)2(4LH2)]n(1) and binuclear [Zn(S2COCy)2]2(4LH2) (2) are described, where4LH2is N,N′-bis(pyridin-4-ylmethyl)ethanediamide. In1, the Zn(S2COEt)2entities are linked by bidentate bridging4LH2ligands through the pyridyl-N atoms to generate a twisted supramolecular chain. As a result of monodentate xanthate ligands, the N2S4donor set defines a distorted tetrahedral coordination geometry and, crucially, allows the participation of the non-coordinating sulfur atoms in supramolecular association. Thus, in the crystal amide-N–H···O(amide) and amide-N–H···S(thione) hydrogen bonds link chains into a three-dimensional architecture. The substitution of the ethyl group in the xanthate ligand with a cyclohexyl group results in very different structural outcomes. In2, a binuclear molecule is observed with the coordination geometry for zinc being defined by chelating xanthate ligands and a pyridyl-N atom with the NS4donor set defining a highly distorted geometry. In the molecular packing, amide-N–H···S(thione) hydrogen bonds stabilise a supramolecular chain along the a-axis and these are connected into a three-dimensional arrangement by methylene-C–H···O and methylene-C–H···π(pyridyl) interactions. The relative importance of the specified intermolecular interactions and weaker, contributing contacts has been revealed by an analysis of the calculated Hirshfeld surfaces of1and2.

C2-Symmetric Hindered “Sandwich” ChiralN-Heterocyclic Carbene Precursors and Their Transition Metal Complexes: Expedient Syntheses, Structural Authentication, and Catalytic Properties

We present here a new family of C2-symmetric “sandwich” NHC ligands abbreviated as SITLAr and BzITLAr and their complexes. The chiral fragments incorporate bulky yet flexible cyclohexyl groups with α-stereocenters joined to nitrogens individually, which set up chiral pockets around pivotal carbene carbons (less than 2.5 A). Full characterization revealed unique structures with roughly parallel aryl moieties above and below imidazoline and benzimidazole planes in the Z-shaped arrangement. Extra hydrogen bonding interactions and steric stress between the square-planar frameworks and aryl groups led to the exceptional confinement and reversed the configurations in the iridium complexes. In accordance with Tolman’s electronic parameters and topographic steric maps of well-established metalated complexes, these new ligands possess strong electron-donating properties and exceptionally steric demands. Additionally, the preliminary results employing the BzITLAr ligands allowed appropriate activities and provided ...

Inversion of Odd-Even Effect Observed in the Crystal Structure of ω-Cyclohexylalkylammonium-[Ni(dmit)2]− Salts

Abstract A previously reported odd-even effect is found to invert by substituting a phenyl with a cyclohexyl group. Crystal structures of [Ni(dmit)2]− complex salts of ω-cyclohexylalkyltrimethylammonium (CncHx; n = 1–5) are revealed by X-ray crystallographic analysis. Alternant stacks are found in all complex salts, but some differences are found in each crystal structure. Terminal cyclohexyl groups adopt chair conformation in the series, and alkylene chains adopt all-trans conformation. Ion pairs found in these crystals are classified by the angle between cations and anions. In these series, odd-even effect is observed in cation length, anion length, Ni-Ni distance and the angle of cation and anion. These are different from the case of terminal methyl and phenyl groups previously reported, indicating that odd-even effect depends on the terminal substituent.

How To Perform Suzuki–Miyaura Reactions of Nitroarene or Nitrations of Bromoarene Using a Pd0 Phosphine Complex: Theoretical Insight and Prediction

Pd0(BrettPhos) (1) was experimentally applied to Suzuki–Miyaura reactions of nitroarenes which occur through oxidative addition of nitroarene (ArNO2) to Pd0. On the other hand, Pd0(tBu-BrettPhos) (2) was experimentally applied to nitrations of bromoarenes which occur through reductive elimination of nitroarene. DFT calculations disclosed that oxidative addition of 4-nitroanisole to 1 was exergonic but that to 2 was endergonic, indicating that 1 is useful for oxidative addition of an Ar–NO2 bond but 2 is useful for reductive elimination of an Ar–NO2 bond. This difference in reactivity between 1 and 2 is explained in that bulky tBu groups on tBu-BrettPhos destabilize the PdII complex PdII(Ar)(NO2)(tBu-BrettPhos) due to large steric repulsion between Ar and tBu-BrettPhos but less bulky cyclohexyl groups on BrettPhos do not. It is theoretically predicted here that NMe2-substituted BrettPhos is better for Ar–NO2 bond cleavage than BrettPhos but xyl-BrettPhos is good for Ar–NO2 formation, as is tBu-BrettPhos, w...

Rhodium/Phosphine catalysed selective hydroformylation of biorenewable olefins

This work reports rhodium catalyzed selective hydroformylation of natural olefins like eugenol, estragole, anethole, prenol and isoprenol using biphenyl based Buchwald phosphine ligands (S‐Phos (L1), t‐Bu XPhos (L2), Ru‐Phos (L3), Johnphos (L4) and DavePhos (L5). Ru‐Phos (L3) ligand exhibited high impact on the hydroformylation of eugenol providing high selectivity (90%) of linear aldehyde as major product. In addition, internal natural olefins like anethole and prenol provided moderate to high selectivity (65% and 85% respectively) of branched aldehydes as a major products. The various reaction parameters such as influence of ligands, P/Rh ratio, syngas pressure, temperature, time and solvents have been studied. A high activity and selectivity gained on the way to the linear aldehydes it may be due to the bulky, steric cyclohexyl and isopropoxy groups present in L3 phosphine ligand. Moreover, this catalytic system was smoothly converting natural olefins into corresponding linear and branched aldehydes with higher selectivity under the mild reaction conditions.

Mechanistic investigations on asymmetric N-H insertion of amines catalyzed by palladium-chiral guanidine complex

The mechanism and stereoselectivity of the asymmetric N-H insertion reactions between α-diazocarbonyl compounds and amines mediated by palladium-chiral guanidine complexes were investigated at the BP86-D3(BJ)/def2TZVP (SMD, CH2Cl2)//BP86-D3(BJ)/def2SVP (SMD, CH2Cl2) level at 303 K. The non-catalytic reaction occurred through a stepwise mechanism, with a high activation barrier of 56.4 kcal mol−1. Good linear correlations between the global nucleophilicity index (N) of amine, Hammett substituent constants (σP), and the activation energy barriers (ΔG≠) were found. The Pd(0)-guanidine-catalyzed reaction consisted of three continuous steps, including: (i) generation of Pd-carbene intermediate by dinitrogen loss from α-diazoesters substrate, (ii) formation of CN bond, and (iii) 1,2-H transfer by metal-associated ylide, accompanying with the regeneration of catalyst. A water molecule accelerated the final H-transfer by constructing hydrogen bonding network. The cyclohexyl group in ligand provided sufficient steric shielding around Pd-carbene intermediate from the re-face attack by amines. The combination of the hydrogen bonding orientation of amide moiety of guanidine ligand, as well as the steric repulsion between the ester group of α-diazoester substrate and bulky CH(Ph)2 group in ligand played an important role in controlling the stereoselectivity, affording the predominant S-configuration product observed in experiment. Introducing one aromatic ring to chiral backbone of the guanidine ligand enhanced the enantiodifferentiation of products by increasing the difference of strain energy (ΔΔEstrain) of Pd-carbene moiety along two competing pathways. Different from Pd(0)-catalyst, the Pd(II)-chiral guanidine complex accelerated N-H insertion reaction via Lewis acid catalysis. In this process, the formation of free ylide in the reaction led to low ee. These results were in good agreement with experimental observations.

Synthesis, structures and anticancer potentials of platinum(II) saccharinate complexes of tertiary phosphines with phenyl and cyclohexyl groups targeting mitochondria and DNA

A series of new Pt(II) saccharinate complexes containing PR3 ligands (PPh3, PPh2Cy, PPhCy2 and PCy3) with progressive phenyl (Ph) replacement by cyclohexyl (Cy) were synthesized and structurally characterized by IR, NMR, ESI-MS and X-ray diffraction. The anticancer activity of the complexes was tested against human breast (MCF-7), lung (A549), colon (HCT116), and prostate (DU145) cancer cell lines as well as against normal bronchial epithelial (BEAS-2B) cells. Trans-configured complexes 1, 3 and 5 emerged as potential anticancer drug candidates. The mechanism of action of the potent complexes was then investigated in detail. The three complexes interacted with DNA by groove binding and with HSA via hydrophobic IIA subdomain. Furthermore, the complexes cleaved plasmid DNA efficiently. Cellular uptake studies in MCF-7 cells showed that the biologically active complexes were mainly localized in cytoplasm. The cytotoxic activity was a function of the lipophilicity and cellular accumulation of the complexes. As determined by M30, Annexin V and Caspase 3/7 activity assays, the complexes induced apoptosis in MCF-7 and HCT116 cells. Mechanistic studies showed that the potent complexes cause excessive generation of reactive oxygen species (ROS) and display a dual action, concurrently targeting both mitochondria and genomic DNA.

Defect-Free Copolymer Gate Dielectrics for Gating MoS2 Transistors

In this study, the poly(2,4,6,8-tetramethyl-2,4,6,8-tetravinylcyclotetrasiloxane-co-cyclohexyl methacrylate) [p(V4D4-co-CHMA)] copolymer was developed for use as a gate dielectric in molybdenum disulfide (MoS2) field-effect transistors (FETs). The p(V4D4-co-CHMA) copolymer was synthesized via the initiated chemical vapor deposition (iCVD) of two types of monomers: 2,4,6,8-tetramethyl-2,4,6,8-tetravinylcyclotetrasiloxane (V4D4) and cyclohexyl methacrylate (CHMA). Four vinyl groups of V4D4 monomers and cyclohexyl groups of CHMA monomers were introduced to enhance the electrical strength of gate dielectrics through the formation of a highly crosslinked network and to reduce the charge trap densities at the MoS2–dielectric interface, respectively. The iCVD-grown p(V4D4-co-CHMA) copolymer films yielded a dielectric constant of 2.3 and a leakage current of 3.8 × 10–11 A/cm2 at 1 MV/cm. The resulting MoS2 FETs with p(V4D4-co-CHMA) gate dielectrics exhibited excellent electrical properties, including an electron ...

Polarization effect in tip-enhanced infrared nanospectroscopy studies of the selective Y5 receptor antagonist Lu AA33810

A novel approach of combining conventional infrared spectroscopy (IR) and atomic force microscopy (AFM) is presented to better understand the behavior of a drug adsorbed on a metal substrate at the nanoscale level. Tip-enhanced infrared nanospectroscopy (TEIRA) was used for the first time to investigate Lu AA33810, a selective brain-penetrating Y5 receptor antagonist, after immobilization on gold nanoparticles (GNPs). Here, a gold coated AFM tip and gold substrate were used to obtain the near-field electromagnetic field trapping effect. Because of the huge signal enhancement, it was possible to obtain the spectral information regarding the self-assembled monolayer of the investigated molecule. The effect of two orthogonal polarizations (p- and s-polarization modulations) of the excitation laser beam on the spectral patterns is also discussed. The results show that there is a strong relationship between the state of polarization of the incident radiation and the relative infrared band intensities. Another factor affecting the observed spectral differences is the topology of the metal substrate, which may result in the induction of a cross-polarization effect. The performed analysis indicates that the C–C bond from the cyclohexyl group is oriented almost parallel to the metal surface. Conversely, the p- and s-polarized spectral variations suggest that the O=S=O angle is high enough to enable the simultaneous interaction of both oxygen atoms with the GNPs.

Hydrophobicity and glutathione peroxidase-like activity of substituted salicyloyl-5-seleninic acids: Re-investigations on aromatic selenium compounds based on their hydrophobicity

Previously we have shown that some of 5-selenized salicylic acid derivatives exhibit glutathione peroxidase (GPx)-like activities higher than or equal to ebselen [Yu et al., Chem. Eur. J., 2008, 14, 7066; Org. Biomol. Chem., 2010, 8, 828]. For understanding the absence of GPx-like activity of the homologue of 5-seleninic anhydride of salicyloylglycine with a loger side chain, we have further synthesized 19 new derivatives (5-seleninic acids of methyl or phenyl salicylates, N-salicyloyl ω-carboxyalkylamines or N-salicyloyl alkyl/phenyl amines, and some of their diselenides). Some of the 5-seleninic acids which carry long side chains or cyclohexyl group have exerted no GPx–like activity, irrespective of whether they are derived from ω-carboxyalkylamines or simple alkylamines. Such lacks of GPx-like activity let us quantitatively relate the GPx-like activities of the congeners of the above 3 series with their hydrophobicity (ClogP), which showed satisfactory correlations in each series. The molecular hydrophobicity was then extensively applied to diverse known aromatic selenium GPx mimics including diaryl diselenides and ebselen derivatives to explain their GPx-like activities in comparably quantitative mode, which could be helpful in designing new improved GPx mimic analogues in each series.

Synthesis, structure-activity relationship and evaluation of new non-polymeric chemical additives based on naphthoquinone derivatives as wax precipitation inhibitors and pour point depressants to petroleum

Wax deposition is one of the major flow problems for petroleum transportation and production. In this context, the development of more efficient methods to remediate paraffin precipitation has received great attention within the oil industries. In the present study, eight new long-chain esters were prepared in less than four synthetic steps and in high yields (84–97%). Seven of them contain naphthoquinone nuclei, and one presents a cyclohexyl group. The new molecules were tested as non-polymer wax precipitation inhibitors and pour point depressants. Calorimetric experiments were employed to identify the effect of four pre-determined chemical groups within the molecules and to set out the best components for maximized inhibition: (i) the length of alkyl chain in the ester group, (ii) the length of the alkyl chain separating the polar nuclei and the ester group, (iii) the heteroatom bonded to the polar nuclei, and (iv) the importance of the naphthoquinone nuclei. After determination of the pour point and wax appearance temperature (WAT) of Brazilian oils by differential scanning calorimetry (DSC), the highest efficiency was observed for naphthoquinone esters derived from stearic and palmitic acids when containing two methylene groups as a separator and nitrogen as the heteroatom. These new additives present better results than the commercially available polymer-based inhibitors in all tested samples, even when applied at smaller concentrations, compared to many other polymer-based inhibitors reported in the literature. The importance of the naphthoquinone moiety as the polar portion of the inhibitor was confirmed when it was replaced by a cyclohexyl group. Molecular modeling and X-ray diffraction studies were also carried out to rationalize the relationship between structure and activity and the action mechanism of these new chemical additives.

Comprehensive Synthesis of Amino Acid-Derived Thiazole Peptidomimetic Analogues to Understand the Enigmatic Drug/Substrate-Binding Site of P-Glycoprotein.

A novel set of 64 analogues based on our lead compound 1 was designed and synthesized with an initial objective of understanding the structural requirements of ligands binding to a highly perplexing substrate-binding site of P-glycoprotein (P-gp) and their effect on modulating the ATPase function of the efflux pump. Compound 1, a stimulator of P-gp ATPase activity, was transformed to ATPase inhibitory compounds 39, 53, and 109. The ATPase inhibition by these compounds was predominantly contributed by the presence of a cyclohexyl group in lieu of the 2-aminobenzophenone moiety of 1. The 4,4-difluorocyclohexyl analogues, 53 and 109, inhibited the photolabeling by [125I]-IAAP, with IC50 values of 0.1 and 0.76 μM, respectively. Selected compounds were shown to reverse paclitaxel resistance in HEK293 cells overexpressing P-gp and were selective toward P-gp over CYP3A4. Induced-fit docking highlighted a plausible binding pattern of inhibitory compounds in the putative-binding pocket of P-gp. The current study underscores the stringent requirement by P-gp to bind to chemically similar molecules.

Performance comparison of chiral separation materials derived from N-cyclohexylcarbonyl and N-hexanoyl chitosans

Chitosan bis(phenylcarbamate)-(N-cyclohexylformamide)s and chitosan bis(phenylcarbamate)-(N-hexanamide)s were synthesized as chiral selectors for enantiomeric separation. Since two types of substituents with different structures were, respectively, introduced onto the 2-position and the 3-/6-positions of the glucose skeleton in the chitosans through a “heterogeneous” modification pathway, the enantioseparation performances of the chiral selectors could be improved. Influence of the type and position of the substituents on chiral recognition and enantioseparation abilities was studied in detail, and the structural dependence on enantioseparation performance was particularly demonstrated. It was found that methyl- and chloro-substituted chitosan bis(phenylcarbamate)-(N-hexanamide)s possessed comparable enantioseparation performances, whereas chloro-substituted chitosan bis(phenylcarbamate)-(N-cyclohexylformamide)s exhibited much more powerful chiral recognition and enantioseparation abilities than the methyl-substituted ones. Among all the prepared chiral selectors, those with the combination of the cyclohexyl group at the 2-position of the glucose skeleton in the chitosan derivatives and the chlorophenyl group at the 3-/6-positions seemed to be more preferable for enantiomeric separation. As a result, the chitosan bis(3,4-dichlorophenylcarbamate)-(N-cyclohexylformamide) possessed the best enantioseparation performance. The solvent tolerability of the prepared chiral selectors was also investigated in the present study. Compared with the classical coated-type chiral separation materials derived from cellulose/amylose derivatives, the N-cyclohexylcarbonyl and N-hexanoyl chitosans based chiral stationary phases were observed to possess more favorable solvent tolerability, thus possibly widening their applications for various practical enantioseparations.

Molecular Nuances Governing the Self-Assembly of 1,3:2,4-Dibenzylidene-d-sorbitol.

1,3:2,4-Dibenzylidene-d-sorbitol (DBS) is the gold-standard for low-molecular-weight organogelators (LMOGs). DBS gels a wide array of solvents, as illustrated by the large Hansen sphere representing gels (2δd = 33.5 MPa1/2, δp = 7.5 MPa1/2, and δh = 8.7 MPa1/2; radius = 11.2 MPa1/2). Derivatives of DBS have been synthesized to isolate and determine molecular features essential for organogelation. In this work, π-π stacking and hydrogen bonding are the major noncovalent interactions examined. The importance of π-π stacking was studied using 1,3:2,4 dicyclohexanecarboxylidene-d-sorbitol (DCHS), which eliminates possible π-π stacking while still conserving the other structural aspects of DBS. The replacement of the benzyl groups with cyclohexyl groups led to a very a poor gelator; only one of the several solvents examined, carbon tetrachloride, formed a gel. 1,3:2,4-Diethylidene-d-sorbitol (DES), another DBS analogue incapable of π-π stacking but with very different polarity, gelated a large Hansen space (2δd = 34.0 MPa1/2, δp = 10.9 MPa1/2, and δh = 10.8 MPa1/2; radius = 9.2 MPa1/2). DES gels solvents with higher δp and δh values than DBS. To assess the role of hydrogen bonding, DBS was acetalated (A-DBS), and it was found that the Hansen space gelated by A-DBS shifted to less polar solvents with higher hydrogen-bonding Hansen solubility parameters (HSPs) (2δd = 33.8 MPa1/2, δp = 6.3 MPa1/2, and δh = 9.6 MPa1/2; radius = 11.1 MPa1/2) than for DBS. These systematic structural modifications are the first step in exploring how specific intermolecular features alter aspects of Hansen space corresponding to positive gelation outcomes.

Effect of alkyl side chains on properties and organic transistor performance of 2,6-bis(2,2′-bithiophen-5-yl)naphthalene

Herein we report the synthesis and characterization of C2-symmetric 2,6-bis(5′-alkyl-2,2′-bithiophen-5-yl)naphthalene derivatives with alkyl side chains of various length and shape, including even the less commonly examined cyclohexyl and cyclohexylalkyl groups. By investigation of how these side chains influence solubility, self-assembly and charge mobility, we aimed to extend the knowledge of structure-function property relationship of the oligothiophene compounds. Charge mobilities observed in this study ranged from 10−3 to 10−1cm2 V−1s−1. The highest values referred to thin layers of derivatives end-capped with linear alkyl chains. XRD methods uncovered OFET-favorable layering of tilted molecular arrangement with the molecular long axes in the out of plane direction. Although the charge mobilities showed variation of as much as two orders of magnitude, XRD measurements of these derivatives revealed similar packing and self-assembly behavior. Hence, the charge mobility differences are more a result of the naturally diverse spatial demands of the tested alkyl groups, with the linear alkyl chains offering the tightest close packing of the π-conjugated backbone. On the other hand, the bulky 2-hexyldecyl group turned out to be the only group that made it possible to avoid insolubility of these derivatives and provided excellent solubility (23mg/mL of chloroform), while the charge mobility remained acceptable even of the spin-coated thin layers.

Aggregation-induced emission, multiple chromisms and self-organization of N-substituted-1,8-naphthalimides

Most aggregation-induced emission (AIE) luminogens possess propeller-like aromatic stator-rotor structures, such as silole, tetraphenylethylene (TPE) and triphenylamine (TPA), to restrict intra-molecular motions (RIM) and avoid aggregation-caused quenching (ACQ) effects. In our work, two simple N-substituted naphthalimides were designed and synthesized by the amide condensation to create novel AIE systems. Except for the same aromatic stator (naphthalimide), N-phenyl-1,8-naphthalimide (PhNI) contained an aromatic rotor (phenyl group) while N-cyclohexyl-1,8-naphthalimide (CyNI) contained an aliphatic rotor (cyclohexyl group). The PhNI samples obtained from different preparation processes showed multiple chromisms (MC) effects and varied levels of luminescence. Despite of the same intra-molecular structure, the crystal of PhNI had staggered parallel inter-molecular conformation with weak emission but the precipitation of PhNI had cross one with strong emission. Although without MC effects, CyNI gave an excellent fluorescence quantum yield (Φf = 0.55). The experimental results and theoretical analyses suggested that the AIE effects were decided by intra- and inter-molecular structure simultaneously and the construction and destruction of inter-molecular π-π stacking between aromatic rotors in PhNI resulted in the MC effects.

Rh(I)-Catalyzed Alkylation of ortho-C-H Bonds in Aromatic Amides with Maleimides.

An alkylation of C-H bonds with maleimides by a rhodium-catalyzed reaction of aromatic amides containing an 8-aminoquinoline moiety as the directing group is reported. Various N-substituents in the maleimide, including methyl, ethyl, cyclohexyl, benzyl, and phenyl groups and even H, are applicable to the reaction. The reaction is highly regioselective at the less hindered ortho-C-H bond when meta-substituted aromatic amides are used as substrates.

Discovery of novel 3-(hydroxyalkoxy)-2-alkylchromen-4-one analogs as interleukin-5 inhibitors

A series of novel chromen-4-one analogs 9a-d and 10a-u was designed, synthesized and evaluated for their IL-5 inhibitory activity. Most of the chromen-4-one analogs showed strong inhibitory activity in low micro molar potency. Among them, 5-(cyclohexylmethoxy)-3-(3-hydroxypropoxy)-2-isopropyl-4H-chromen-4-one (10t, 90.0% inhibition at 30 μM, IC50 = 5.5 μM, CLogP = 4.76887) and 2-cyclohexyl-5-(cyclohexylmethoxy)-3-(3-hydroxypropoxy)-4H-chromen-4-one (10u, 95.5% inhibition at 30 μM, IC50 = 3.0 μM, CLogP = 5.96187) showed the best inhibition. The structure activity relationship reveals that the hydrophobic cyclohexylmethoxy group at the position 5 of the chromen-4-one ring A is preferable than at position 6 and the dual hydrogen bonding acceptor property on the chromen-4-one ring should be important for the inhibitory activity. In addition, the optimum length of the side chain at position 3 of chromen-4-one ring is critical for the donation of hydrogen to the binding site and the 3-hydroxypropoxy group showed the best activity. Moreover, the conformational restrictor (isopropyl, cyclohexyl group) at position 2 is much more favorable for the formation of effective conformer of side chain with hydrogen bonding donor property of these chromen-4-one analogs.

Effects on Rotational Dynamics of Azo and Hydrazodicarboxamide-Based Rotaxanes.

The synthesis of novel hydrogen-bonded [2]rotaxanes having two pyridine rings in the macrocycle and azo- and hydrazodicarboxamide-based templates decorated with four cyclohexyl groups is described. The different affinity of the binding sites for the benzylic amide macrocycle and the formation of programmed non-covalent interactions between the interlocked components have an important effect on the dynamic behavior of these compounds. Having this in mind, the chemical interconversion between the azo and hydrazo forms of the [2]rotaxane was investigated to provide a chemically-driven interlocked system enable to switch its circumrotation rate as a function of the oxidation level of the binding site. Different structural modifications were carried out to further functionalize the nitrogen of the pyridine rings, including oxidation, alkylation or protonation reactions, affording interlocked azo-derivatives whose rotation dynamics were also analyzed.