Catalyst deactivation by sintering significantly reduces productivity and energy efficiency of the chemical industry and the effectiveness of environmental cleanup processes. It also hampers the introduction of novel energy conversion devices such as fuel cells. The use of experimental techniques that allow the scrutiny of sintering in situ at high temperatures and pressures in reactive environments is a key to alleviate this situation. Today, such techniques are, however, lacking. Here, we demonstrate by monitoring the sintering kinetics of a Pt/SiO2 model catalyst under such conditions in real time that indirect nanoplasmonic sensing (INPS) has the potential to fill this gap. Specifically, we show an unambiguous correlation between the optical response of the INPS sensor and catalyst sintering. The obtained data are analyzed by means of a kinetic model accounting for the particle-size-dependent activation energy of the Pt detachment. Ostwald ripening is identified as the main sintering mechanism.

3-Aminopropyl functionalised silica gel may be readily transformed into a stable immobilised palladium catalyst. This catalyst was then successfully employed in a series of fast, copperfree Sonogashira coupling reactions.

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Asymmetric alkynylation reactions to linear alkyl and substituted aromatic aldehydes have been accomplished in good yields and with a range of selectivities. For aromatic aldehydes we observed that the selectivity of the alkynylation reaction appears to depend upon the substituents on the aromatic ring. Thus with electron-withdrawing substituents both the yield and enantioselectivities were good to excellent. In contrast to this, the presence of electron-donating groups provided excellent conversions; however, these were coupled with poor enantioselectivities.In a recent paper 1 we revealed a diastereoselective cobaltmediated synthesis of benzopyrans using a novel variation of an intramolecular Nicholas 2 reaction in the key step. Using this chemistry we were able to access a number of functionalised benzopyran derivatives 2, which were then subsequently screened against cromakalim 3 3, a known modulator of potassium channels (Scheme 1).In our efforts to achieve an enantioselective Nicholas reaction 4 we have focussed upon the synthesis of optically active propargyl alcohols, based upon 1, for use in benzopyran synthesis. The ability to transfer the stereochemical information, contained within a dicobalt hexacarbonyl complexed chiral propargyl alcohol, into the resulting product still remains a challenge to the synthetic chemist. This limitation has been explained by the fluxional nature of a cobalt-stabilised carbocation that exposes both faces to the incoming nucleophile 5 thus leading to racemisation. One solution to this racemisation process lies in the ability to rapidly quench the cation before delocalisation effects take place. The first example of an enantiospecific Nicholas reaction, a process which provided chiral products from chiral substrates, was disseminated in 1994. 6 In the same year the rapid racemisation of a cobalt-stabilised cation was exploited to afford a stereoselective synthesis of fused-ring systems. 7 Chiral propargyl alcohols may be prepared via the asymmetric reduction of ynones 8 or from the asymmetric addition of alkynes to aromatic aldehydes. 9 Although the catalytic enantioselective addition reaction of dialkyl and alkenyl zinc reagents to aldehydes may be carried out efficiently, using a wide range of catalysts, advancements with the corresponding asymmetric alkynylation reaction appears to be far less developed. 10 The major limitations seem to be based upon a combination of factors such as the need to employ stoichiometric amounts of catalyst/ ligand, limitations in the availability of appropriate reagents such as chiral ligands and, in some examples, the production of significant quantities of by-products. 11From our inspection of the existing literature, in this interesting area of asymmetric synthesis, we were able to corroborate the inconsistencies in the percentage yields and/ or enantioselectivities for asymmetric alkynylation reactions. For instance with aldehydes such as 4 (Figure 1), with R = alkyl, good to excellent yields for the alkynylation reaction have been repor...