Cyclohexyl Ethyl Research Articles

Rigid biphenyl-contained epoxy resins with improved thermal resistant properties

Biphenyl-contained monomer of 1,4-bis[2-(3,4-epoxy cyclohexyl ethyl) dimethylsilyl] biphenyl (BP-SiH-EP) was prepared via hydrosilylation reaction of 1,4-bis(dimethylsilyl) biphenyl (BP-SiH) and 1,2-epoxy-4-vinylcyclohexane in the presence of Karstedt’s catalyst. 1H-NMR, 13C-NMR and FTIR were used to characterize the structure of the obtained monomer. BP-SiH-EP was then cured by methyl hexahydrophthalic anhydride (MeHHPA) with 1-cyanoethyl-2-ethyl-4-methylimidazole as an accelerator. The polymerization behavior was studied by DSC. The results of DMA measurement demonstrate that the cured BP-SiH-EP/MeHHPA can maintain high storage modulus (> 1 GPa) in a wide range of temperature up to 176 °C. According to the damping factor curve of DMA, cured BP-SiH-EP/MeHHPA exhibits a high glass transition temperature (T g) of 192 °C, which is 20 °C higher than that of cured 1,4-bis[2-(3,4-epoxy cyclohexyl ethyl) dimethylsilyl] benzene (DEDSB)/MeHHPA. TGA results show that cured BP-SiH-EP/MeHHPA has good thermal stability (T 5% = 339 °C) due to the high heat-resistance of rigid biphenyl group. Moreover, the crosslinking density of cured BP-SiH-EP/MeHHPA should be lower than that of cured DEDSB/MeHHPA estimated from their chemical structures, which conflicts with the calculated results based on the rubber elasticity equation. The inconsistence indicates that the calculated crosslinking densities are not comparable, possibly owing to their differences in the rigidity of polymer chains and intermolecular interaction.

Selective engineering using Mg–Al calcined hydrotalcite and microwave irradiation in mono-transesterification of diethyl malonate with cyclohexanol

Selectivity engineering aspects of synergism between microwave irradiation and solid base catalysis is investigated for a highly selective mono-transesterification of diethyl malonate with cyclohexanol using Mg–Al calcined hydrotalcite as catalyst. Microwave irradiation showed threefold increase in cyclohexanol conversion vis-a-vis conventional heating and only the mono-transesterified product was obtained. The catalyst was characterised by XRD, FT-IR, CO2-TPD, surface area and pore size analysis. Hydrotalcite with Mg:Al composition as 3:1 gave the best results. Effect of various parameters was studied on conversion and selectivity. Under optimised reaction conditions, 69% conversion with 98% selectivity for cyclohexyl ethyl malonate was obtained for catalyst loading of at 100°C in 2h. The catalyst showed excellent reusability. Complete theoretical and experimental analysis has been done to develop a kinetic model for the reaction.

Synthesis and calcium channel antagonist activity of new 1,4-dihydropyridine derivatives containing dichloroimidazolyl substituents.

A group of dialkyl, dicycloalkyl and diaryl ester analogues of nifedipine (CAS 21829-25-4), in which the ortho-nitrophenyl group at position 4 is replaced by a 4,5-dichloroimidazolyl substituent, were synthesized and evaluated as calcium channel antagonists using the high K+ contraction of guinea-pig ileal longitudinal smooth muscle. The results for the symmetrical esters in alkyl esters series showed that increasing the length of the methylene chain in C3 and C5 ester substituents (from n = 0 to n = 2) increased the activity. When increasing of the length was accompanied by increase of the hindrance, the activity decreased. In the unsymmetrical diester series, the results showed when R1 is a small substituent (R1 = Me), increasing of the lipophilic property in R2 substituent increases the activity if this high lipophilicity is not accompanied by steric hindrance. The results demonstrate that in the unsymmetrical series, several compounds (benzyl methyl, benzyl isopropyl and cyclohexyl ethyl) had activity similar to that of the reference drug nifedipine. In symmetrical diesters compounds, the most active compound was the diphenethyl ester derivative being more active than nifedipine. These structure-activity data indicate that the 4-(4,5-dichloroimidazolyl) moiety is the bioisoester of 3-nitrophenyl and 2,3-dichlorophenyl moieties.

H‐Aggregation Strategy in the Design of Molecular Semiconductors for Highly Reliable Organic Thin Film Transistors

AbstractFour new quaterthiophene derivatives with end‐groups composed of dicyclohexyl ethyl (DCE4T), dicyclohexyl butyl (DCB4T), cyclohexyl ethyl (CE4T), and cyclohexyl butyl (CB4T) were designed. All materials showed high solubility in common organic solvents. UV–vis absorption measurements showed that the quaterthiophene derivatives with asymmetrically substituted cyclohexyl end‐groups (CE4T and CB4T) preferred H‐type aggregation whereas those with symmetrically substituted cyclohexyl end‐groups (DCE4T and DCB4T) preferred J‐type aggregation. The molecular structure‐dependent packing (H or J) of the new quaterthiophene derivatives was analyzed by grazing‐incidence wide‐angle X‐ray scattering (GIWAXS) measurements. The field‐effect mobilities of devices that incorporated the asymmetrical molecules, CE4T and CB4T, were quite high, above 10−2 cm2 V−1 s−1, due to H‐aggregation, whereas the field‐effect mobilities of devices that incorporated symmetrical molecules, DCE4T and DCB4T, were poor, below 10−4 cm2 V−1 s−1, due to J‐aggregation. More importantly, H‐aggregation within the thin film provided stable crystalline morphologies in the spin‐coated films, and, thus, thin film transistors (TFTs) using cyclohexylated quaterthiophenes yielded highly reproducible transistor performances. The distributions of measured field‐effect mobilities in transistors based on cyclohexylated quaterthiophenes with H‐aggregation were remarkably narrow.

Modified Acetal Approach to 157nm Resist Design.

Optical absorbance data on a variety of acetal-derivatized hydroxystyrene based polymers are reported at 157nm. Acetals based on tertiary butyl, cyclohexyl ethyl and a silicon-derivative show improved transparency of the corresponding polymers compared with the parent hydroxystyrene backbone. Silicon-acetal demonstrated capability to resolve 80nm dense trenches in a bilayer resist system. No silicon outgassing was observed upon 157nm exposure. The resist also displayed excellent O2/SO2-etch properties.

Stereochemistry of halopyridyl and thiazolyl thiourea compounds is a major determinant of their potency as nonnucleoside inhibitors of HIV-1 reverse transcriptase

Chiral derivatives of two cyclohexylethyl halopyridyl thiourea compounds (HI-509 and HI-510), two α-methyl benzyl halopyridyl compounds (HI-511 and HI-512), and a cyclohexyl ethyl thiazolyl thiourea compound (HI-513) were synthesized as nonnucleoside inhibitors (NNI) of human immunodeficiency virus (HIV) reverse transcriptase (RT). The R stereoisomers of all five compounds inhibited the recombinant RT in vitro with 100-fold lower IC 50 values. HI-509 R, HI-510 R, HI-511 R, HI-512 R and HI-513 R were active anti-HIV agents and inhibited HIV-1 replication in human peripheral blood mononuclear cells at nanomolar concentrations, whereas their enantiomers were inactive. Each of these five compounds was also active against NNI-resistant HIV-1 strains, with HI-511 R being the most active agent. When tested against the NNI-resistant HIV-1 strain A17 with a Y181C mutation in RT, HI-511 R was found to be 10,000-times more active than nevirapine, 5000-times more active than delavirdine, and 50-times more active than trovirdine. HI-511 R inhibited the HIV-strain A17 variant, containing RT mutations Y181C plus K103N, with an IC 50 value of 2.7 μM, whereas the IC 50 values of nevirapine, delavirdine, and trovirdine against this highly NNI-resistant HIV-1 strain were >100 μM.

Hydrodehalogenation of Halogenated Aryl Ketones under Multiphase Conditions. 6. pH Effect on the Chemoselectivity and Preliminary Mechanistic Investigation

A model halogenated aryl ketone (4-chloropropiophenone 1) was subjected to mild catalytic hydrodehalogenation (p[H2] = 1 atm, T = 50 °C) in a multiphase system consisting of isooctane and an alkaline aqueous phase, in the presence of onium salts as phase-transfer agents. The chemoselectivity of the reaction was sharply influenced by the KOH concentration of the aqueous phase: thus, the formation of 1-phenyl-1-propanol 4 was favored in a highly alkaline pH range (>13.5 by 50% to 5% KOHaq). Instead, up to 95% selectivity toward phenyl ethyl ketone 2 was observed if the pH was controlled (8 < pH < 13) by adjusting the KOHaq concentration in the range between 5 and 1%. Further investigation of the pH effect indicated that an acidic aqueous phase directed the reaction chemoselectivity toward the formation of products arising from aromatic ring reduction (i.e., cyclohexyl ethyl ketone 7 and 1-cyclohexyl-1-propanol 8) rather than from carbonyl hydrogenation or hydrogenolysis. Also aliphatic amines, used in place of the PT onium salt, afforded good selectivities toward 2, although not as high as the ones obtained with Aliquat 336.

Conformationally constrained [p-(omega-aminoalkyl)phenacetyl]-L-seryl-L-lysyl dipeptide amides as potent peptidomimetic inhibitors of Candida albicans and human myristoyl-CoA:protein N-myristoyl transferase.

MyristoylCoA:protein N-myristoyltransferase (NMT) covalently attaches the 14-carbon saturated fatty acid myristate, via an amide bond, to the N-terminal glycine residues of a variety of cellular proteins. Genetic studies have shown that NMT is essential for the viability of the principal fungal pathogens which cause systemic infection in immunosuppressed humans and hence is a target for development of fungicidal drugs. We have generated a class of potent peptidomimetic inhibitors of the NMT from one such fungal pathogen, Candida albicans. The N-terminal tetrapeptide from a substrate analog inhibitor, ALYASKL-NH2, was replaced with an omega-aminoalkanoyl moiety having an optimal 11-carbon chain for inhibition (11-aminoundecanoyl-SKL-NH2, 3a, IC50 = 1.2 +/- 0.14 microM). A series of replacements for the C-terminal Leu established that residues containing a lipophilic side chain were most effective, with cyclohexylalanine having the greatest potency (3g, IC50 = 0.36 +/- 0.06 microM). Removal of the carboxamide moiety led to a metabolically stable dipeptide inhibitor containing an N-(cyclohexylethyl)lysinamide (17e, IC50 = 0.11 +/- 0.03 microM). Partial rigidification of the flexible aminoundecanoyl chain produced the dipeptide p-(omega-aminohexyl)phenacetyl-L-seryl-L-lysyl-N-(cyclohexyleth yl)amide (26b, IC50 = 0.11 +/- 0.04 microM). Subsequent incorporation of an alpha-methyl substituent into 26b provided the dipeptide analog [2-[p-(omega-aminohexyl)phenyl]propionyl]-L-seryl-L-lysyl-N-(cyclohex ylethyl)amide, a very potent inhibitor (48, IC50 = 0.043 +/- 0.006 microM), which retained the three essential elements required for recognition by the acyl transferase's peptide binding site.

Temperature-dependent changes in the 19F NMR spectra of perfluorocyclohexyl ethers

Temperature-dependent high-resolution 19F NMR spectroscopic investigations of perfluoro(cyclohexyl methyl ether) ( 1), perfluoro(cyclohexyl ethyl ether) ( 2) and perfluoro[4-(2-cyclohexyloxyethyl)morpholine] ( 3) revealed in each case dynamic phenomena traced back to the occurrence of two interconvertible conformers, one clearly prevalent at both lower and higher temperatures. The bulky R fO substituent of the favoured conformer is in the equatorial position. The energy difference between the conformers amounts to 2.9 to 4.5 kJ mol −1, and the free enthalpy of activation for the interconversion reaction was estimated to be 57.4 kJ mol −1 for 1, 56.2 kJ mol −1 for 2 and 53.9 kJ mol −1 for 3.

Stereoselective synthesis of β-hydroxy-α-methylketones via [formula omitted]- and [formula omitted]-vinyloxyboranes generated directly from cyclohexyl ethyl ketone

E - and Z -dialkylvinyloxyboranes, prepared directly from cyclohexyl ethyl ketone, undergo stereo-selective aldol condensations to provide threo - erythro -β-hydroxy-α-methylketones, respectively.