Profiling the Major Aroma-Active Compounds of Microwave-Dried Jujube Slices through Molecular Sensory Science Approaches.

To discriminate the aroma-active compounds in dried jujube slices through microwave-dried treatments and understand their sensory attributes, odor activity value (OAV) and detection frequency analysis (DFA) combined with sensory analysis and analyzed through partial least squares regression analysis (PLSR) were used collaboratively. A total of 21 major aromatic active compounds were identified, among which 4-hexanolide, 4-cyclopentene-1,3-dione, 5-methyl-2(5H)-furanone, 4-hydroxy-2,5-dimethyl-3(2H)furanone, 3,5-dihydroxy-2-methyl-4-pyrone were first confirmed as aromatic compounds of jujube. Sensory evaluation revealed that the major characteristic aromas of dried jujube slices were caramel flavor, roasted sweet flavor, and bitter and burnt flavors. The PLSR results showed that certain compounds were related to specific taste attributes. 2,3-butanedione and acetoin had a significant positive correlation with the roasted sweet attribute. On the other hand, γ-butyrolactone, 4-cyclopentene-1,3-dione, and 4-hydroxy-2,5-dimethyl-3(2H)furanone had a significant positive impact on the caramel attributes. For the bitter attribute, 2-acetylfuran and 5-methyl-2(5H)-furanone were positively correlated. Regarding the burnt flavor, 5-methyl-2-furancarboxaldehyde and 3,5-dihydroxy-2-methyl-4-pyrone were the most influential odor-active compounds. Finally, 2-furanmethanol and 2,3-dihydro-3,5-dihydroxy-6-methyl-4H-pyran-4-one were identified as the primary sources of the burnt and bitter flavors. Importantly, this work could provide a theoretical basis for aroma control during dried jujube slices processing.

A one-step base-free synthesis of N-arylamides via modified pivaloyl mixed anhydride mediated amide coupling.

Pivalic anhydride is shown to be an effective reagent for direct amidation of carboxylic acids with N-alkyl anilines. The only by-product of this reaction is nontoxic pivalic acid, which can be easily removed by aqueous workup. The reactions are conducted under mild conditions and found to be compatible with a range of carboxylic acids, including aromatic, heterocyclic, acrylic, and aliphatic carboxylic acids and amino acids generating the desired amides in short reaction times.

Complementary Oxidative Generation of Iminyl Radicals from α-Imino-oxy Acids: Silver-Catalyzed C-H Cyanoalkylation of Heterocycles and Quinones.

A complementary and general strategy for the oxidative generation of iminyl radicals from the readily available α-imino-oxy acids has been established through silver-catalyzed decarboxylation. To demonstrate its synthesis utility, the direct C-H cyanoalkylation of heterocycles and quinones with cyclic α-imino-oxy acids via the iminyl radical-mediated C-C bond cleavage is developed. This cost-effective method takes place under mild reaction conditions and exhibits a broad substrate scope.

General 5-Halomethyl Isoxazoline Synthesis Enabled by Copper-Catalyzed Oxyhalogenation of Alkenes.

A general and efficient oxyhalogenation of unsaturated ketoximes has been achieved through copper catalysis with diethyl bromomalonate, N-chlorosuccinimide, and N-iodosuccinimide, yielding 5-chloromethyl, 5-bromomethyl, and 5-iodomethyl isoxazolines in good to excellent yields.

Metal-free TBAI-catalyzed arylsulfonylation of activated alkenes with sulfonylhydrazides.

An efficient metal-free oxidative arylsulfonylation of α,ß-unsaturated imides with sulfonylhydrazides leading to isoquinoline-1,3(2H,4H)-dione derivatives has been developed. The procedure involves the generation of sulfonyl radicals via cleavage of the S-N bond of sulfonylhydrazides with sulfonylation and C-H functionalization. The protocol uses the economical and environmentally friendly TBAI-TBHP catalytic system, and the corresponding isoquinoline-1,3(2H,4H)-diones with various functional groups were obtained in moderate to good yields.

A rapid and effective approach for on-site assessment of total carotenoid content in wolfberry juice during processing.

BACKGROUND: Carotenoid content analysis in wolfberry processed products has mainly focused on the determination of zeaxanthin or zeaxanthin dipalmitate, which cannot indicate the total carotenoid content (TCC) in wolfberries. RESULTS: We have exploited an effective approach for rapid extraction of carotenoid from wolfberry juice and determined TCC using UV-visible spectrophotometry. Several solvent mixtures, adsorption wavelengths of carotenoid extracts and extraction procedures were investigated. The optimal solvent mixture with broad spectrum polarity was hexane-ethanol-acetone (2:1:1) and optimal wavelength was 456 nm. There was no significant difference of TCC in wolfberry juice between direct extraction and saponification extraction. CONCLUSION: The developed method for assessment of TCC has been successfully employed in quality evaluation of wolfberry juice under different processing conditions. This measurement approach has inherent advantages (simplicity, rapidity, effectiveness) that make it appropriate for obtaining on-site information of TCC in wolfberry juice during processing.

Preparation of silica-based nanoparticle having surface-bound octanoyl-aminopropyl moieties and its applications for the capillary electrochromatography separation of charged and neutral compounds.

A kind of novel amphiphilic silica-based nanoparticle having surface-bound octanoyl-aminopropyl moieties (OA-NP) with the diameter of ~250 nm was successfully prepared and characterized by elemental analysis, Fourier transform infrared spectrometry. The potential use of OA-NP as pseudostationary phase in capillary electrochromatography for the separation of aromatic acids, basic, and neutral compounds was investigated. Five aromatic acids were separated rapidly with high column efficiency as they migrate in the same direction with the EOF under optimum experimental conditions. Under a running buffer with the composition of 40% methanol, 10 mM phosphate buffer (pH 5.5) with 1.0 mg/mL OA-NPs added, basic compounds investigated were baseline resolved with relatively symmetrical peaks. Due to the existence of polar acyl amide group on the surface of OA-NPs, "silanol effect" that occurs between the positively charged basic analytes and the silanols of the capillary column was greatly suppressed. Furthermore, the newly synthesized OA-NPs were also tried for the separation of some neutral analytes, and satisfactory separations were obtained.

Monitoring supported-nanocluster heterogeneous catalyst formation: product and kinetic evidence for a 2-step, nucleation and autocatalytic growth mechanism of Pt(0)n formation from H2PtCl6 on Al2O3 or TiO2.

A pressing problem in supported-metal-nanoparticle heterogeneous catalysis--despite the long history and considerable fundamental as well as industrial importance of such heterogeneous catalysts--is how to monitor such catalysts' formation more routinely, rapidly, and in real time. Such information is needed to better control the size, shape, composition, and thus resultant catalytic activity, selectivity, and lifetime of these important catalysts. To this end, a study is reported of the formation of supported Pt(0)(n) nanoparticles by H(2) reduction of H(2)PtCl(6) on Al(2)O(3) (or TiO(2)) to give 6 equivalents of HCl plus supported Pt(0)(n)/Al(2)O(3) (or Pt(0)(n)/TiO(2)), all while in contact with a solution of EtOH and cyclohexene. The HCl and Pt(0)(n) products were confirmed, respectively, by the stoichiometry of HCl formation using pH(apparent) measurements, appropriate standards, and by TEM and EDX measurements. The hypothesis of this research is that the kinetics of formation of this supported heterogeneous catalyst could be successfully monitored by a fast cyclohexene hydrogenation catalytic reporter reaction method first worked out for monitoring transition-metal nanoparticle formation in solution (Watzky, M. A. and Finke, R. G. J. Am. Chem. Soc. 1997, 119, 10382-10400). Significantly, sigmoidal kinetics of Pt(0)(n)/Al(2)O(3) catalyst formation were in fact successfully monitored by the catalytic hydrogenation reporter reaction method and then found to be well fit to the Finke-Watzky (hereafter F-W) 2-step, slow continuous nucleation and then autocatalytic surface growth mechanism, A --> B (rate constant k(1)) and A + B --> 2B (rate constant k(2)), respectively, in which A is the H(2)PtCl(6) and B is the growing, catalytically active Pt(0) nanoparticle surface. The finding that the F-W mechanism is applicable is significant in that it, in turn, suggests that the > or = 8 insights from studies of the mechanisms of soluble nanocluster formation can likely also be applied to supported heterogeneous catalyst synthesis, including a recent equation that gives nanocluster size vs time in terms of k(1), k(2), [A](o) and other parameters (Watzky, M. A., Finney, E. E. and Finke, R. G. J. Am. Chem. Soc. 2008, 130, 11959-11969 ). Also presented are the use of the catalytic reporter reaction to reveal H(2) gas to-solution mass-transfer-limitations (MTL) in the system of H(2)PtCl(6) on TiO(2), results relevant to a recent communication in this journal. The use of the F-W 2-step nucleation and autocatalytic growth kinetic model to fit 3 literature examples of heterogeneous catalyst formation, involving H(2) reduction of both supported or bulk M(x)O(y) (i.e., and in gas-solid reactions), are also presented as part of the Supporting Information. A conclusion section is then provided summarizing the insights and caveats from the present work, as well as some needed future studies.