Oh my Gold! Gold atoms stabilise catalytically active palladium nanoparticles when engaged in an alloy heterogenised on carbon. The increased durability makes the Pd-Au/C catalyst more recyclable than the gold-free Pd/C catalyst for the Sonogashira reaction.
SummaryThis paper describes the preparation of indoles, azaindoles and benzofurans in pure water by using a new heterogeneous Pd–Cu/C catalyst through a cascade Sonogashira alkynylation–cyclization sequence. Details of the optimization studies and the substrate scope are discussed. This procedure allows the preparation of heterocycles with good yields and is tolerant to a wide variety of functional groups.
A homologous series of two-station [2]rotaxanes incorporating amino-acid units in the molecular thread has been developed. The degenerate [2]rotaxanes exhibit amino-acid specific shuttling rates between two fumaric stations related to the steric factor associated to the amino-acid side chain, as [a
In this study, investigation is focused on the soluble part of oak heartwood colour, with the objective of defining its impact on the colour of spirits after a barrel ageing. Colour is an important parameter for estimating the quality of many beverages and food items. Acetone with 30% water permitted a fast and complete extraction of the soluble colouring matter of heartwood. Water is necessary to improve the extraction of wood fibres by hydration. In heartwood, the repartition of colour is heterogeneous. The outer heartwood, which is new wood, presents a lower soluble colour than the inner heartwood, which is older. This difference is due to the polymerisation by oxidation of the ellagitannins during the natural process of wood ageing and the copolymerisation of cell-wall polymers as polysaccharides.
Electronic Supplementary Information (ESI) available: experimental procedures, characterization data of 1, 2, and 4 (1 H, 13 C, VT NMR) and molecular modeling structures of rotaxanes 1, 7, 8 and 9. Macrocyclic Hamilton receptor-shuttling dynamics in [2]rotaxanes Inherent movement of a macrocycle comprising a multi-site hydrogen bonding Hamilton-type receptor in a series of [2]rotaxanes was investigated by dynamic and VT NMR. In these rotaxanes the varying nature and number of hydrogenbond motifs and stations on the molecular axles influenced ring dynamics. Triazole stations interact selectively by hydrogen bonding with the isophthalamide amide bonds present in the Hamilton macrocycle and fast shuttling (72 kHz at 25 °C) was observed in a two station variant.
scite is a Brooklyn-based organization that helps researchers better discover and understand research articles through Smart Citations–citations that display the context of the citation and describe whether the article provides supporting or contrasting evidence. scite is used by students and researchers from around the world and is funded in part by the National Science Foundation and the National Institute on Drug Abuse of the National Institutes of Health.