Carbonyl Bond Research Articles

Stereochemical Peculiarities of the Products of Condensation of Piperidine-4-one with Aromatic Aldehydes

<p>This paper presents the results of investigations on conformation peculiarities of the condensation products of piperidine-4-ones containing arylidene, hydroxyarylmethyl as well as both arylidene and hydroxyarylmethyl substituents. Synthesized α, β-unsaturated ketones can be used to investigate conformation of cycles fixing a conjugated system of carbonyl and double bonds. Synthesis of α, β-unsaturated piperidine-4-ones was carried out according to the reaction of Claisen-Schmidt by condensation of piperidine-4-ones with aromatic aldehydes. The reaction was carried out in methanol medium in the presence of an alkaline agent. High resolution <sup>1</sup>H and <sup>13</sup>C NMR resonance assignments and conformational assignments were carried out for four 3- arylidene or hydroxyarylmethyl and 3-arylidene-5- hydroxyarylmethyl substituted piperidine-4-ones (1-4). As a result of the initial aldol condensation of piperidine-4-ones with aromatic aldehydes an aryloxymethyl group in the intermediate compound can have both an equatorial and axial position. Conformation of a conjugated system proved to be electronically effected by the presence of nitrogen atom in the heterocycle. At the same time, conformation peculiarities of α, β-unsaturated ketones under study are developed at the stage of their synthesis. This is explained by the fact that in the course of the reaction there appears a new sp2-centre, this resulting in our case in the change of the conformation of “a chair”. There takes place flattening of the structure and fixation of s-cis conformation. Furfurilidene substituent is conjugated with a carbonyl group, there forms a planar structure including 2, 3, 4 and 5 atoms of hydrogen of piperidine cycle and furfurilidene substituent and there exist two isomers with cis- (A) and trans- (B) position of a furyl ring at double bond in relation to a carbonyl group.</p>

Simulated Temperature Programmed Desorption of Acetaldehyde on CeO2(111): Evidence for the Role of Oxygen Vacancy and Hydrogen Transfer

The temperature programmed desorption of acetaldehyde adsorbed on partially reduced CeO2(111) has been studied in detail using microkinetic modeling based on self-consistent, periodic density functional theory calculations at the GGA-PW91+U level. Previous experimental studies (Chen et al. J. Phys. Chem. C 115: 3385, 2011; Calaza et al. J. Am. Chem. Soc. 134: 18034, 2012) have shown that, whereas on fully oxidized CeO2(111) acetaldehyde desorbs molecularly with a peak temperature of 210 K, the polymerization and enolization of acetaldehyde dominate the surface reactivity on partially reduced CeO2(111), resulting in acetaldehyde desorption at higher temperatures. Here we propose a comprehensive reaction mechanism that is consistent with the spectroscopic evidence of the identities of the surface intermediates and with the observed desorption activities, including the formation of ethylene and acetylene. Besides acetaldehyde (CH3CHO) and its enolate (CH2CHO), several other C2H x O species are proposed as key intermediates which are not seen spectroscopically, including ethoxy (CH3CH2O), ethyleneoxy (CH2CH2O), and formylmethylene (CHCHO). Our study suggests that oxygen vacancies play the critical role of activating the carbonyl bond and thereby facilitating β C–H bond scissions in acetaldehyde, leading to enolization, intermolecular hydrogen transfer, deoxygenation, and potentially C–C coupling reactions.

A Critical Test of the Electrostatic Contribution to Catalysis with Noncanonical Amino Acids in Ketosteroid Isomerase.

The vibrational Stark effect (VSE) has been used to measure the electric field in the active site of ketosteroid isomerase (KSI). These measured fields correlate with ΔG(⧧) in a series of conventional mutants, yielding an estimate for the electrostatic contribution to catalysis (Fried et al. Science 2014, 346, 1510-1513). In this work we test this result with much more conservative variants in which individual Tyr residues in the active site are replaced by 3-chlorotyrosine via amber suppression. The electric fields sensed at the position of the carbonyl bond involved in charge displacement during catalysis were characterized using the VSE, where the field sensitivity has been calibrated by vibrational Stark spectroscopy, solvatochromism, and MD simulations. A linear relationship is observed between the electric field and ΔG(⧧) that interpolates between wild-type and more drastic conventional mutations, reinforcing the evaluation of the electrostatic contribution to catalysis in KSI. A simplified model and calculation are developed to estimate changes in the electric field accompanying changes in the extended hydrogen-bond network in the active site. The results are consistent with a model in which the O-H group of a key active site tyrosine functions by imposing a static electrostatic potential onto the carbonyl bond. The model suggests that the contribution to catalysis from the active site hydrogen bonds is of similar weight to the distal interactions from the rest of the protein. A similar linear correlation was also observed between the proton affinity of KSI's active site and the catalytic rate, suggesting a direct connection between the strength of the H-bond and the electric field it exerts.

Selective Cobalt-Catalyzed Reduction of Terminal Alkenes and Alkynes Using (EtO)2Si(Me)H as a Stoichiometric Reductant.

While attempting to effect Co-catalyzed hydrosilylation of β-vinyl trimethylsilyl enol ethers we discovered that depending on the silane, solvent and the method of generation of the reduced cobalt catalyst, a highly efficient and selective reduction or hydrosilylation of an alkene can be achieved. This paper deals with this reduction reaction, which has not been reported before in spite of the huge research activity in this area. The reaction, which uses an air-stable [2,6-di(aryliminoyl)pyridine)]CoCl2 activated by 2 equivalents of NaEt3BH as a catalyst (0.001-0.05 equiv) and (EtO)2SiMeH as the hydrogen source, is best run at ambient temperature in toluene and is highly selective for the reduction of simple unsubstituted 1-alkenes and the terminal double bonds in 1,3- and 1,4-dienes, β-vinyl ketones and silyloxy dienes. The reaction is tolerant of various functional groups such as a bromide, alcohol, amine, carbonyl, and di or trisubstituted double bonds, and water. Highly selective reduction of a terminal alkyne to either an alkene or alkane can be accomplished by using stoichiometric amounts of the silane. Preliminary mechanistic studies indicate that the reaction is stoichiometric in the silane and both hydrogens in the product come from the silane.

Evaluation of Tribological Properties of Sulfur- and Phosphorous-Free Quinolinium Salts and Their Correlation with Quantum Chemical Parameters

ABSTRACTFor developing antiwear additives with high efficiency but with low sulfated ash, phosphorous, and sulfur (SAPS), N-substituted quinolinium halides, [DIP-Q]+Br− [DIP-Q=1-(3-(1,3-dioxoisoindolin-2-yl)propyl)quinolon-1-ium], [DIE-Q]+Br− [DIE-Q=1-(3-(1,3-dioxoisoindolin-2-yl)ethyl)quinolon-1-ium], [P-Q]+I− [P-Q=propylquinolon-1-ium], and [M-Q]+I− [M-Q=methylquinolon-1-ium] have been prepared and characterized by 1H- and 13C-NMR spectroscopic techniques. The tribological performance of these quinolone-based quaternary salts as antiwear additives in paraffin oil has been assessed on a four-ball test rig. The observed results have been compared with those of zinc dialkyldithiophosphate (ZDDP), a high SAPS additive. The tribotesting of these additives has been performed using 1% w/v additives concentration at different loads and times. The potential of these compounds as antiwear additives is evident from their observed tribological data: mean wear scar diameter (MWD), friction coefficient (µ), mean wear volume (MWV), and wear rates. All of the quinolinium derivatives prove to be better antiwear additives than ZDDP. Among the tested synthesized compounds, [DIP-Q]+Br− exhibits the best tribological behavior followed by [DIE-Q]+Br−, [P-Q]+I−, and [M-Q]+I−. The surface topography of worn surface studied by scanning electron microscopy (SEM) and atomic force microscopy (AFM) shows that surface roughness is reduced to a greater extent in case of quinolinium derivatives than lubrication with ZDDP or base oil alone. Energy-dispersive X-ray (EDX) and X-ray photoelectron spectroscopy (XPS) analysis of worn surfaces in the presence of quinolinium additives shows that the tribofilm is composed of FeBr3, Fe3O4, and organic compounds containing carbonyl and imine bonds. Theoretical investigations using quantum chemical calculations are indicative of significant chemical interactions of these quinolinium additives with metal surfaces, which is strongly supported by the observed experimental data.

One-pot synthesis of Pd nanoparticles on ordered mesoporous Al2O3 for catalytic hydrogenation of 2-ethyl-anthraquinone

Pd/Al2O3 catalysts were synthesized via one-pot evaporation-induced self-assembly and hydrothermal methodology, and the conventional impregnation method. XRD, N2 adsorption-desorption and TEM showed that the one-pot synthesized catalyst, especially evaporation-induced self-assembly one (EISA-Pd/Al2O3) possesses the large specific surface area, ordered mesopores with the narrow pore size distribution and well-dispersed Pd particles encapsulated inside the mesopores of Al2O3. Catalytic hydrogenation of 2-ethyl-anthraquinone (EAQ) to form anthrahydroquinone at 0.3MPa and 70°C showed that EISA-Pd/Al2O3 exhibits superior performance, with the improvement of 50% in the selectivity and 82% in the activity compared with the impregnated catalyst. The high selectivity is due to the increased electron density of Pd particles and lower amount of acid sites measured by NH3-TPD, which had an inhibitory effect on the formation of the by-product and degradation products. The high activity could be ascribed to the higher proportion of linear carbonyls which has a positive correlation with low-coordinated Pd atoms, characterized by in situ FTIR. DFT calculations revealed that the high activity of the defective Pd surface with low-coordinated Pd atoms is due to the larger adsorption energy and longer length of carbonyl bond of EAQ adsorbed on it than on the perfect Pd surface.

Evaluating the Free Energies of Solvation and Electronic Structures of Lithium-Ion Battery Electrolytes.

Adaptive biasing force molecular dynamics simulations and density functional theory calculations were performed to understand the interaction of Li(+) with pure carbonates and ethylene carbonate (EC)-based binary mixtures. The most favorable Li carbonate cluster configurations obtained from molecular dynamics simulations were subjected to detailed structural and thermochemistry calculations on the basis of the M06-2X/6-311++G(d,p) level of theory. We report the ranking of these electrolytes on the basis of the free energies of Li-ion solvation in carbonates and EC-based mixtures. A strong local tetrahedral order involving four carbonates around the Li(+) was seen in the first solvation shell. Thermochemistry calculations revealed that the enthalpy of solvation and the Gibbs free energy of solvation of the Li(+) ion with carbonates are negative and suggested the ion-carbonate complexation process to be exothermic and spontaneous. Natural bond orbital analysis indicated that Li(+) interacts with the lone pairs of electrons on the carbonyl oxygen atom in the primary solvation sphere. These interactions lead to an increase in the carbonyl (C=O) bond lengths, as evidenced by a redshift in the vibrational frequencies [ν(C=O)] and a decrease in the electron density values at the C=O bond critical points in the primary solvation sphere. Quantum theory of atoms in molecules, localized molecular orbital energy decomposition analysis (LMO-EDA), and noncovalent interaction plots revealed the electrostatic nature of the Li(+) ion interactions with the carbonyl oxygen atoms in these complexes. On the basis of LMO-EDA, the strongest attractive interaction in these complexes was found to be the electrostatic interaction followed by polarization, dispersion, and exchange interactions. Overall, our calculations predicted EC and a binary mixture of EC/dimethyl carbonate to be appropriate electrolytes for Li-ion batteries, which complies with experiments and other theoretical results.

Kimyasal yöntem ile indirgenmiş grafen oksit sentezi ve karakterizasyonu

More recently, graphene, having outstanding electrical, mechanical, thermal and optical properties, have become an important research topic. Reduced graphene oxide (RGO) is one of the most effective way to obtain the graphene. In this study, RGO was obtained by reduction of graphene oxide (GO) synthesized by a modified Hummers method. The transparent structures of RGO have been identified through SEM images. The ratio of carbon (C) was found to be approximately 89% by SEM/EDX analysis. It was proven by FT-IR analysis that hydroxyl, carbonyl, epoxy and alkoxy bonds in GO structure were removed from RGO structure. On the other hand, RAMAN spectroscopic studies showed that the new sp 2 structures occurred, and the amount of regular structures increased. XRD analysis indicated that d-spacing between the layers of RGO decreased from 0,83 nm to 0,36 nm due to the degradation of functional groups during the chemical process, which were formed in the oxidation process.

Crystal structure of 16-ferrocenylmethyl-3β-hydroxy-estra-1,3,5(10)-trien-17-one: a potential chemotherapeutic drug.

A new ferrocene complex, 16-ferrocenylmethyl-3β-hy-droxy-estra-1,3,5(10)-trien-17-one dimethyl sulfoxide monosolvate, [Fe(C5H5)(C24H27O2)]·C2H6OS, has been synthesized and structurally characterized by single-crystal X-ray diffraction techniques. The mol-ecule crystallizes in the space group P21 with one mol-ecule of dimethyl sulfoxide. A hydrogen bond links the phenol group and the dimethyl sulfoxide O atom, with an O⋯O distance of 2.655 (5) Å. The ferrocene group is positioned in the β face of the estrone moiety, with an O-C-C-C torsion angle of 44.1 (5)°, and the carbonyl bond length of the hormone moiety is 1.216 (5) Å, typical of a C=O double bond. The average Fe-C bond length of the substituted Cp ring [Fe-C(Cp*)] is similar to that of the unsubstituted one [Fe-C(Cp)], i.e. 2.048 (3) versus 2.040 (12) Å. The structure of the complex is compared with those of estrone and eth-oxy-methyl-estrone.

Surface oxygen micropatterns on glow discharge polymer targets by photo irradiation

Recent simulations predict surface oxygen may be a significant source of disruptive perturbations in the implosion process of glow-discharge polymers (GDP) ablators at the National Ignition Facility. GDP material held in ambient atmospheric conditions showed an increase in mass when stored in light transparent containers, which suggests that photo exposure is a driving force for oxygen absorption. To investigate if surface oxygen is a contributing factor of disruptive perturbations during implosion, a method to imprint a periodic micropattern of oxygen on the surface of GDP was developed and used to fabricate a flat sample for empirical testing. Photo exposure using collimated blue light was used to generate micropatterns of surface oxygen on the GDP material. The periodic oxygen micropattern was confirmed by secondary ion mass spectrometry (SIMS) and energy dispersive spectroscopy. A SIMS depth profile showed the atomic percent of oxygen ranged from 8 at. % near the surface to 1 at. % at a depth of 2 μm in a sample exposed for 4 min. The molecular interactions formed between the GDP and oxygen molecules were characterized using Fourier transform infrared resonance (FTIR), which showed the formation of hydroxyl (O–H) and carbonyl (C=O) bonds. The FTIR enabled the oxygen mass uptake as a function of photo exposure time to be quantified (resolved to typically 0.05 at. % oxygen). This experimental protocol was then applied to produce a GDP flat part with a periodic 75 μm wavelength micropattern of photo exposed (oxygen rich) and masked (oxygen deficient) regions. The micropatterned GDP ablators developed in this work are being used to assess the effect of surface oxygen on disruptive perturbations during the inertial confinement fusion implosion process.

Biodegradation of low density polyethylene (LDPE) modified with dye sensitized titania and starch blend using Stenotrophomonas pavanii

Plastic goods including plastic shopping bags, which are generally made from low density polyethylene (LDPE), are a cause of considerable environmental nuisance. Development of a material that would degrade, due to simple factors i.e. sunlight and/or biotic factors, in the open environment, is therefore, of considerable interest. Biodegradation of photodegraded and non-photodegraded LDPE films, modified with food grade dye sensitized titania (TiO2) nanoparticles and starch blend, was evaluated under laboratory conditions. Bacterial strains were isolated from solid waste dump site using enrichment culture and two step screening procedure for their ability to degrade LDPE. Bacterial strains capable of growing in the LDPE-Titania environment were further screened for their ability to form biofilm on LDPE films, salt aggregation test (SAT) and cell surface hydrophobicity. The potential bacterial strains were then identified as Pseudomonas aeruginosa (CA9), Burkholderia seminalis (CB12), and Stenotrophomonas pavanii (CC18) (GenBank accession number KR738718, KR738720 and KR738722, respectively) based on the 16S rRNA gene sequence homology. The strain CC18 showed highest biofilm, hydrophobicity and growth rate. The LDPE films of 3 × 3 cm were incubated with CC18 in mineral salt media (MSM) for 56 days. The viability tests of the isolates grown on LDPE surface were performed which also correlated with the protein density of biomass (R2 = 0.98). LDPE films were characterized using SEM, TGA, XRD and FTIR before and after incubation. Biodegradation of LDPE was confirmed by an increase in the Keto Carbonyl, Ester Carbonyl and Vinyl Bond Index compared to control. The results conclusively demonstrated the potential of the LDPE-titania-starch blend for production of shopping bags which may easily be degraded in open environment after use.

Protonated Phosphazenes: Structures and Hydrogen‐Bonding Organocatalysts for Carbonyl Bond Activation

AbstractThe synthesis and application of protonated phosphazeniums as hydrogen‐bond donor groups was demonstrated in the solid state and in solution. In particular, their catalytic activity was shown in the activation of the carbonyl group within cyclic esters, using a benchmark reaction, that is, in the ring‐opening polymerization of lactide and valerolactone, in the presence of a basic co‐catalyst. The reactions proceed differently depending on monomers and/or phosphazenium salts. The impact of catalysts and reactants steric hindrance upon the outcome of the reaction is then highlighted and discussed.magnified image

Crystal structures of (1E,4E)-1,5-bis-(5-bromo-thio-phen-2-yl)-2,4-di-methyl-penta-1,4-dien-3-one and (E)-4-(5-bromo-thio-phen-2-yl)-1,3-di-phenyl-but-3-en-2-one.

The title compounds, C15H12Br2OS2, (I), and C20H15BrOS, (II), were synthesized by employing Claisen-Schmidt condensation of pentan-3-one and di-benzyl-acetone with 5-bromo-thio-phene-2-carbaldehyde in the presence of methano-lic KOH. Even though 1:2 products were expected in both of the reactions, 1:2 and 1:1 products were obtained as (I) and (II), respectively. In (I), the two methyl groups are trans to each other, 29.5 (7) and 28.7 (7)° away from the central carbonyl bond between them, whereas the two phenyl rings of di-benzyl-acetone subtend a dihedral angle of 53.09 (18)°. In the crystal of (I), C-H⋯O hydrogen bonds define mol-ecular chains along c. A second type of mol-ecular chain is formed along b by means of C-Br⋯π inter-actions. These two families of mol-ecular chains are stacked by π-π inter-actions, forming a three-dimensional supra-molecular architecture. In (II), similar C-H⋯O hydrogen bonds as in (I) define inversion dimers, whilst C-H⋯.π inter-actions build a staircase structure along the a axis.

Engineering biphasic janus-type polymer-protein nanofibers via centrifugal jet spinning

Event Abstract Back to Event Engineering biphasic janus-type polymer-protein nanofibers via centrifugal jet spinning Alex Khang1, Prashanth Ravishankar1, Patrick K. Anderson1 and Kartik Balachandran1 1 University of Arkansas, Biomedical Engineering, United States Introduction: This project aims to create a tissue-engineering scaffold with bi-phasic Janus-type structural and biological properties. The key goal was to create a fiber scaffold with biphasic properties on each side. In this project we aim to explore ways to control Janus-type biphasic behavior as it pertains to fiber alignment, diameter, mechanical properties and cell adhesion properties of the scaffold. Materials: The polymers and proteins utilized were polycaprolactone (PCL) and gelatin, respectively. Seven percent solutions of differing PCL/gelatin ratios were dissolved in Hexafluoro-2-propanol (HFIP) (Pure PCL, 3:1, 2:1, 1:1, 1:2, 1:3, and Pure Gelatin). Methods: A double reservoir with orifices towards the bottom of each reservoir was used to extrude Janus nanofiber scaffolds, with one side having pure PCL composition and the other containing the aforementioned blends of PCL/gelatin. A commercially available motor was used to spin the reservoir at various RPMs (20k, 25k, and 30k) and the extruded fibers were collected. Alignment and fiber diameter of the nanofiber scaffolds were assessed via analysis of Scanning Electron Microscope (SEM) images of the fibers. The physical and chemical presence of Janus-type biphasic properties was assessed using Fourier Transform Infrared (FTIR) Spectroscopy. Results: Our results indicate a direct correlation between higher RPMs and creating fibers with increased alignment and decreased fiber diameter. Additionally, the presence of bi-phasic Janus fibers has been confirmed both using SEM imaging and surface property measurements with Fourier Transform Infrared Spectroscopy. Figure 2a displays a SEM image of a representative scaffold showing biphasic Janus-characteristics at the individual nanofiber level. Figure 2b displays a representative FTIR Spectrogaph of a fiber scaffold that was Pure PCL on one side and a ratio of PCL:Gelatin (3:1) on the other side. Both sides display a prominent absorbance peak at ~1750cm-1 which reflects the carbonyl bond of PCL. However the absorbance peak is much less in magnitude on the biohybrid side due to the incorporation of gelatin. The biohybrid side displays additional absorbance bands at ~1650cm-1 and 1545cm^-1 which reflect the amide 1 and amide 2 bonds of gelatin. This result documents the presence of biphasic Janus character at the macro-level in the scaffold constructs. Discussion: Our results have successfully demonstrated the fabrication of scaffolds with Janus-type behavior at the macro and single fiber levels. We did discover that Janus character was reduced as fabrication RPM increased, and we hope to explore this phenomenon in future studies. Additionally, the results on alignment and diameter were in agreement with studies published on singlephase jet-spun nanofibers[1]. Conclusion: This study highlights the potential to create scaffolds that provide different properties on either side. With these biphasic Janus type fibers, the mechanical and chemical make up of the constructs can potentially be tuned to facilitate numberous tissue engineering applications. Future studies will include exploring the relationship between fabrication parameters and hydrophobicity of the two surfaces of these constructs and exploring the viability of the scaffolds with living cells. State Undergraduate Research Fellowship; Institute for Nanoscience and Engineering, University of Arkansas; Prof. Xianghong Qian, University of Arkansas

Chemistry of 1,5-diketones: V. Hydrazination of acyclic and heterocyclic (poly)carbonyl compounds

Reactions of 2-(1-aryl-3-oxo-3-phenylpropylidene)-3,4-dihydronaphthalen-1(2H)-ones, 3-(1-aryl-3-oxo-3-phenylpropyl)-3,4-dihydro-2H-chromene-2,4-diones, and 3,3'-(arylmethylene)bis(3,4-dihydro-2H-chromene-2,4-diones) with hydrazine hydrate have been studied. Depending on the substrate structure, these reactions involve intramolecular heterocyclization with participation of the exocyclic double bond and sidechain carbonyl group or both oxo groups to give new pyrazole, indazole, and diazepine derivatives, as well as hydrazones.

ChemInform Abstract: A Reaction of Triazoles with Thioesters to Produce β‐Sulfanyl Enamides by Insertion of an Enamine Moiety into the Sulfur—Carbonyl Bond.

N-Sulfonyl-1,2,3-triazoles react with thioesters in the presence of a rhodium(II) catalyst to produce β-sulfanyl enamides in a stereoselective manner. The reaction proceeds through generation of an α-imino rhodium carbene complex, nucleophilic addition of the sulfur atom of a thioester onto the carbenoid carbon atom, and subsequent intramolecular migration of the acyl group from the sulfur atom to the imino nitrogen atom. The method is successfully applied to a ring-expansion reaction of thiolactones, thus leading to the formation of sulfur-containing lactams.

A Reaction of Triazoles with Thioesters to Produce β-Sulfanyl Enamides by Insertion of an Enamine Moiety into the Sulfur-Carbonyl Bond.

N-Sulfonyl-1,2,3-triazoles react with thioesters in the presence of a rhodium(II) catalyst to produce β-sulfanyl enamides in a stereoselective manner. The reaction proceeds through generation of an α-imino rhodium carbene complex, nucleophilic addition of the sulfur atom of a thioester onto the carbenoid carbon atom, and subsequent intramolecular migration of the acyl group from the sulfur atom to the imino nitrogen atom. The method is successfully applied to a ring-expansion reaction of thiolactones, thus leading to the formation of sulfur-containing lactams.

A Reaction of Triazoles with Thioesters to Produce β‐Sulfanyl Enamides by Insertion of an Enamine Moiety into the Sulfur–Carbonyl Bond

AbstractN‐Sulfonyl‐1,2,3‐triazoles react with thioesters in the presence of a rhodium(II) catalyst to produce β‐sulfanyl enamides in a stereoselective manner. The reaction proceeds through generation of an α‐imino rhodium carbene complex, nucleophilic addition of the sulfur atom of a thioester onto the carbenoid carbon atom, and subsequent intramolecular migration of the acyl group from the sulfur atom to the imino nitrogen atom. The method is successfully applied to a ring‐expansion reaction of thiolactones, thus leading to the formation of sulfur‐containing lactams.

Nucleophilic addition of (difluoromethyl)trimethylsilane to selected α-imino ketones and aryl diketones

Chemoselective addition of (difluoromethyl)trimethylsilane (CHF2SiMe3) to the carbonyl bond of aryl glyoxal derived α-imino ketones, and selected diaryl 1,2-diketones were studied in the presence of initiators, such as potassium tert-butoxide or caesium fluoride. Subsequent reduction of the obtained α-imino alcohols and α-hydroxy ketones with sodium borohydride gave the expected 2-amino 1-(difluoromethyl)alcohols and (difluoromethyl)-1,2-diols respectively in moderate to good yields. High de values were observed for the reduction of α-(difluoromethyl)-α-hydroxy ketones.

Room temperature atomic layerlike deposition of ZnS on organic thin films: Role of substrate functional groups and precursors

The room temperature atomic layerlike deposition (ALLD) of ZnS on functionalized self-assembled monolayers (SAMs) was investigated, using diethyl zinc (DEZ) and in situ generated H2S as reactants. Depositions on SAMs with three different terminal groups, –CH3, –OH, and –COOH, were studied. It was found that the reaction of DEZ with the SAM terminal group is critical in determining the film growth rate. Little or no deposition is observed on –CH3 terminated SAMs because DEZ does not react with the methyl terminal group. ZnS does deposit on both –OH and –COOH terminated SAMs, but the grow rate on –COOH terminated SAMs is ∼10% lower per cycle than on –OH terminated SAMs. DEZ reacts with the hydroxyl group on –OH terminated SAMs, while on –COOH terminated SAMs it reacts with both the hydroxyl and carbonyl bonds of the terminal groups. The carbonyl reaction is found to lead to the formation of ketones rather than deposition of ZnS, lowering the growth rate on –COOH terminated SAMs. SIMS spectra show that both –OH and –COOH terminated SAMs are covered by the deposited ZnS layer after five ALLD cycles. In contrast to ZnO ALLD where the composition of the film differs for the first few layers on –COOH and –OH terminated SAMs, the deposited film composition is the same for both –COOH and –OH terminated SAMs. The deposited film is found to be Zn-rich, suggesting that the reaction of H2S with the Zn-surface adduct may be incomplete.