The simple α,β-unsaturated ketones and 2-pyrones are readily available synthetically important dienophiles dienes, respectively, for Diels−Alder reactions. However, both prove to be challenging substrates catalytic asymmetric By exploring a new catalysis strategy featuring cooperative with cinchona catalysts, an unprecedented reaction of has been successfully developed. With broad scopes reactants, the provides direct versatile access wide range structurally novel bicyclic chiral building...

ADVERTISEMENT RETURN TO ISSUEPREVArticleNEXTPlatinum-catalyzed asymmetric hydroformylation of olefins with (-)-BPPM/SnCl2-based catalyst systemsJohn K. Stille, Heng Su, Philippe Brechot, Giovanni Parrinello, and Louis S. HegedusCite this: Organometallics 1991, 10, 4, 1183–1189Publication Date (Print):April 1, 1991Publication History Published online1 May 2002Published inissue 1 April 1991https://pubs.acs.org/doi/10.1021/om00050a060https://doi.org/10.1021/om00050a060research-articleACS...

One-dimensional nanostructure-based chemiresistive sensors have received great attention because of their compact design and excellent sensing performance, including high sensitivity, low detection limits, power consumption, the ability to integrate multisensor arrays. However, these generally suffer from slow response recovery times when they are operated at ambient conditions catalytic or absorption/desorption processes. The overcome this obstacle by operating temperature, which increases...

Metal/DNA/SWNT hybrid nanostructure-based gas sensor arrays were fabricated by means of ink jet printing metal ion chelated DNA/SWNTs on microfabricated electrodes, followed electroless deposition to reduce ions metal. DNA served as a dispersing agent effectively solubilize pristine SWNTs in water and chelating centers for the formation nanoparticles. Noble metals including palladium, platinum, gold used because high binding affinity toward specific analytes enhances selectivity sensitivity....

In this work, glutaraldehyde-crosslinked chitosan (GCC) was prepared and its ability to remove 2,4-dichlorophenoxyacetic acid (2,4-D) from aqueous solutions systematically studied.

ADVERTISEMENT RETURN TO ISSUEPREVArticleNEXTSynthesis of large-ring keto lactones by the homogeneous and polymer-supported palladium-catalyzed carbonylative coupling esters having vinyl triflate vinylstannane terminiJohn K. Stille, Heng Su, Dale H. Hill, Philippe Schneider, Masahide Tanaka, Donald L. Morrison, Louis S. HegedusCite this: Organometallics 1991, 10, 6, 1993–2000Publication Date (Print):June 1, 1991Publication History Published online1 May 2002Published inissue 1 June...

Abstract Achiral epoxides are isomerized to optically active allylic alcohols under the influence of catalytical amounts cob(I) alamin in protic polar solvents.

A highly flexible and conductive nanohybrid film based on multi-walled carbon nanotube (MWNT) was prepared using synergistic dispersion effects of nanosisal cellulose graphene oxide (GO). The effect MWNT characterized illustrative diagrams different dispersions after centrifuge, transmission electron microscope, Zeta potential, respectively. results showed that 80 wt% efficiently dispersed formed a stable nanodispersion solution 10 nanofiber (CNF) GO as dispersants. conductivity tensile...

Air pollution is a serious environmental and health issue that necessitates accurate timely air-quality monitoring to provide warnings affected demographics as regulatory tool for reduction of emission. Thus, high-density sensor array was developed detection quantification NO2, SO2, O3—three contributing air pollutants used Quality Index (AQI). The gas operates on the principle chemiresistive sensing with light-tunable selectivity sensitivity which achieved by combining chemical photoactive...

Tin oxide functionalized single-walled carbon nanotubes (SWNTs) were synthesized on prefabricated microelectrodes by an electrochemical process. The shape, morphology, valence state and crystal structure of tin controlled varying the deposition potential (E), charge density (C), subsequent calcining temperature (T) their structure-related sensing performance toward ammonia (NH3) gas was characterized at 25°C. Optimal obtained under conditions E = −0.625 V, C 0.125 C/cm2, T 400°C. underlying...

Graphene has attracted great interest due to its extensive applications in optoelectronic and electronic circuits devices. However, reduction of graphene oxide (GO) is a process which hydrophilic GO converts hydrophobic graphene. Very little known about the aggregation cause performance degradation by general chemical methods as single reaction medium presents difficulty satisfying good dispersion simultaneously. In this paper, we report mixed alkylphenol polyoxyethylene (7) ether (OP-7)...

In this paper, the oxidation–exfoliation process of graphite is studied experimentally by mixed-solvent method, simulated theoretically, and it found that Graphene Oxide (GO) a Janus structure with inconsistent oxidation on both surfaces; hydrophilic one side hydrophobic other side. This layer spacing are due to sides which changes polarity different solvent mixtures. We used two-phase system benzyl alcohol water, as well controlling surface substrate, achieve (using mixed solution GO has...

Preliminary studies toward the assembly of a gold-polypyrrole (PPy) peapod-like chemiresistive ammonia (NH3) gas sensors are presented. The proposed synthesis process will use electropolymerization to embed gold nanoparticles in polypyrrole nanowires. Viral-templating and PPy electrodeposition via cyclic voltammetry focus this investigation. A gold-binding M13 bacteriophage was used as bio-template assemble continuous chains on interdigitated Pt working electrodes. dimensions resulting...

Abstract Pt and SnO 2 were co‐functionalized on single‐walled carbon nanotubes (SWNTs) assembled microelectrodes by electrochemical deposition where nanoparticle's morphology, size, density tuned controlling the applied potential time. The systematic study to obtain optimum condition for Pt‐decorated /SWNTs (Pt/SnO /SWNTs) performed also correlate with its CO sensing performance. Illumination‐dependent performance was examined using red, green UV LED as light sources at room temperature....

Abstract A method for optimizing the design of heterogeneous gas chemiresistor arrays to maximize classification accuracy is presented. The features used include coefficients from a Fast Fourier Transform, properties piecewise representation response shape, and characterizing time. novel time are designed be insensitive noise sensor drift. This work introduces approach leveraging experimental data create large synthetic datasets training classifiers. Pairs time‐series measurements randomly...

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An effective method for the Diels-Alder reaction of simple α,β-unsaturated ketones with 2-pyrones is reported. For this transformation readily available cinchona alkaloid-derived catalysts 1a or 1b in combination TFA were used. Various adducts obtained high yields, diastereoselectivities and enantiomeric ratios. The highly chemoselective, furnishing predominantly rather than Michael product. presumably proceeds via an iminium ion intermediate.