A general approach to N-heterocyclic scaffolds using domino Heck-aza-Michael reactions

Palladium-catalyzed domino Heck–aza-Michael reactions for the synthesis of a series of C1-substituted tetrahydro-β-carbolines, tetrahydroisoquinolines and isoindolines are described. The domino process involves the initial intermolecular Heck reaction of an aryl bromide with an electron deficient alkene, followed by an intramolecular aza-Michael reaction to form the new N-heterocycle in high yield.

A one-pot, three-component approach to functionalised tetrahydroisoquinolines using domino Heck-aza-Michael reactions

A one-pot, three-component method incorporating a domino Heck–aza-Michael reaction has been developed for the rapid synthesis of functionalised tetrahydroisoquinolines. Following the in situ generation of an acrylamide, a domino process involving intermolecular Heck reaction and subsequent intramolecular aza-Michael addition affords tetrahydroisoquinolines bearing C1-acetamide functionality.

Mechanisms of light producing chemical reactions

An array of experimental and computational methods has been implement to elucidate the mechanisms of light producing chemical reactions that are important in nature and the laboratory.

The facet selectivity of inorganic ions on silver nanocrystals in etching reactions

The facet selectivity of the halide ions and chlorauric acid for several shaped silver nanocrystals is presented in this paper. Two inorganic ions show different representations when they are used for etching silver nanocrystals in the self-sacrificial template reaction. The morphological changes of the silver nanocrystals indicate that the halide ions prefer to etch the (110) facets of silver nanocrystals, while in the chlorauric acid etching reaction, gold first modifies the (110) facets and then lets chlorauric acid etch the (111) facets instead. The selective facet etching on individual nanoparticles in the solution phase has crucial significance in the control-synthesis of nanocrystals and the facet asymmetric reaction.

Investigating ionic effects applied to water based organocatalysed aldol reactions

Saturated aqueous solutions of various common salts were examined for their effect on aqueous aldol reactions catalysted by a highly active C₂-symmetric diprolinamide organocatalyst developed in our laboratory. With respect to the aldol reaction between cyclohexanone and 4-nitrobenzaldehyde, deionised water was always a superior medium to salt solutions though some correlation to increasing anion size and depression in enantiomeric excess could be observed. Additionally, the complete inhibition of catalyst activity observed when employing tap water could be alleviated by the inclusion of ethylenediaminetetraacetate (EDTA) into the aqueous media prior to reaction initiation. Extension of these reaction conditions demonstrated that these ionic effects vary on a case-to-case basis depending on the ketone/aldehyde combination.

Emotional reactions to real-world events in social networks

A convergence of emotions among people in social networks is potentially resulted by the occurrence of an unprecedented event in real world. E.g., a majority of bloggers would react angrily at the September 11 terrorist attacks. Based on this observation, we introduce a sentiment index, computed from the current mood tags in a collection of blog posts utilizing an affective lexicon, potentially revealing subtle events discussed in the blogosphere. We then develop a method for extracting events based on this index and its distribution. Our second contribution is establishment of a new bursty structure in text streams termed a sentiment burst. We employ a stochastic model to detect bursty periods of moods and the events associated. Our results on a dataset of more than 12 million mood-tagged blog posts over a 4-year period have shown that our sentiment-based bursty events are indeed meaningful, in several ways.

Leaving the professional tennis circuit : exploratory study of experiences and reactions from elite female athletes

In 2002, Tennis Australia commissioned a report into the experiences of elite female past players on leaving the professional tennis circuit. Australian players who were in the top 800 of the Women’s Tennis Association (WTA) end of year rankings and who had left the professional circuit within the previous 15 years were asked by mail to respond to a questionnaire. The questionnaire asked players to describe their feelings about leaving the tour during the time leading up to leaving the tour to two years after retirement. The main findings of the study suggested that those who planned to leave the tour found the transition process easy, whereas those who did not plan to leave the tour found the process difficult. Most players (66%) did not regret leaving the tour, and, although the remaining players responded that they regretted leaving, none attempted a comeback. Tennis Australia has implemented strategies to assist current players on the professional tour based on the results of this study.

Direct asymmetric aldol reactions in water catalysed by a highly active C2-Symmetrical bisprolinamide organocatalyst

A novel C2-symmetrical bisprolinamide organocatalyst was synthesised and used to facilitate asymmetric direct aldol reactions in a water emulsion. Reactions were performed at room temperature with very low catalyst loadings (12.5 mol%) without the required use of additives, co-catalysts or extended reaction times (24 h). This catalyst system was then used with a variety of aldehyde substrates showing good reaction generality for benzaldehydes with cyclohexanone (dr range 77/23 to >99/1, anti/syn; ee range 33% to >99%) and moderate scope with cyclopentanone (dr range 45/55 to 76/24, anti/syn; ee range 14% to 68%). Ultra-low catalysts loadings (0.1 and 0.05 mol%) were also investigated demonstrating catalyst turnover numbers in the order of 1000.

Reactions of Nb2 and Nb3 with CO, D2, N2, and O2 : reconciling experimental kinetics with density functional theory-calculated reaction profiles

 Calculated energy profiles for the reactions of neutral Nb₂ and Nb₃ metal clusters with CO, D₂, N₂, and O₂ are presented. In each reaction path, both a physisorption energy minimum, where the reactant remains intact, and a chemisorption energy minimum, where the reactant has dissociated, are calculated and linked by saddle points. We calculate branching ratios for the forward (dissociative) and reverse reactions which we compare with the experimental kinetic data. It is found that a combination of average thermal energies and barrier heights leads to wide variation in branching ratios which compares favourably to previously determined experimental reaction rates.

Insight into reactions and interface between boron nitride nanotube and aluminium

Nature and mechanism of interfacial reactions between boron nitride nanotubes (BNNTs) and aluminum matrix at high temperature (650 °C) are studied using high-resolution transmission electron microscopy (HRTEM). This study analyzes the feasibility of the use of BNNTs as reinforcement in aluminum matrix composites for structural application, for which interface plays a critical role. Thermodynamic comparison of aluminum (Al)-BNNT with analogous Al-carbon nanotube (Al-CNT) system reveals lesser amount of reaction in the former. Experimental observation also reveals thin (~7 nm) reaction-product formation at Al-BNNT interface even after 120 min of exposure at 650 °C. The spatial distribution of the reaction-product species at the interface is governed by the competitive diffusion of N, Al, and B. Morphology of the reaction products are influenced by their orientation relationship with BNNT walls. A theoretical prediction on Al-BNNT interface in macroscale composite suggests the formation of strong bond between the matrix and reinforcement phase.