Dual-Catalytic Transition Metal Systems for Functionalization of Unreactive Sites of Molecules

Catalytic reactions occur readily at sites of starting materials that are both innately reactive and sterically accessible or that are predisposed by a functional group amenable to direct a catalyst. However, selective reactions at unbiased sites of substrates remain challenging and typically require additional pre-activation steps or the use of highly reactive reagents. Herein, we report dual-catalytic transition metal systems that merge a reversible activation cycle with a functionalization cycle, together enabling functionalization of substrates at their inherently unreactive sites. By engaging the Ru- or Fe-catalyzed equilibrium between an alcohol and an aldehyde, Pd-catalyzed b-arylation of aliphatic alcohols and Rh-catalyzed g-hydroarylation of allylic alcohols were developed. The mild conditions, functional group tolerance and broad scope of the methodologies (81 examples) demonstrate the synthetic applicability of the dual-catalytic systems. In a broader context, this work highlights the potential of the multi-catalytic approach to address challenging transformations to circumvent the multi-step procedures and the use of highly reactive reagents in organic synthesis.</b

Effects of different management practices of organic uphill grasslands on the abundance and diversity of soil mesofauna

In this study the effect of different grassland managements (cattle grazing with different intensities and mowing) on soil mesofauna, i.e. mites (Acari) and springtails (Collembola), was studied. Mites and springtails are the most numerous representatives of soil mesofauna organisms living in the upper soil layers (up to 5 cm). Soil mesofauna groups or species are commonly used as bioindicators of soil health. The experiment was carried out from 2007 to 2009 in the West Sudety Mountains, Poland. Pastures and meadows were under organic farming management, without pesticides or synthetic fertilizers, and restricted livestock density. Soil samples were taken three times a year (in May−June, July and October) from pastures grazed at different frequencies: once, twice and four times a year, alternate management (grazed and mown pasture) and mown meadow. Mites were identified according to orders or suborders (Oribatida, Gamasida, Prostigmata, Astigmata), while springtails to the species level. The data were analysed using a general linear model (GLM). The mesofauna taxa in relation to the treatment and date were analysed with the canonical correspondence analysis (CCA). The data from three years showed that most soil mesofauna assemblages occurred in significantly higher numbers on the pasture grazed once or twice and on alternate managed pasture than in pasture grazed four times a year and mown meadow. The CCA analysis showed the preference of most springtail species to pasture grazed once a year, while mites preferred pasture grazed twice a year and alternate management. The number of species and the abundance of the most numerous species (Protaphorura pannonica, Desoria multisetis and Folsomides parvulus) did not differ significantly between treatments. To summarize, cattle grazing once or twice a season or alternate management (grazing and mowing once a season) have a positive impact on soil mesofauna

Bispalladium(II) Complexes of di‐ p ‐Pyrirubyrin Derivatives as Promising Near‐Infrared Photoacoustic Dyes

The insertion of palladium(II) into di‐p‐pyrirubyrin results in mutually convertible bimetallic complexes. Post‐synthetic functionalization of one of them yielded bispalladium(II) dioxo‐di‐p‐pyrirubyrin and, after demetallation, dioxo‐di‐p‐pyrirubyrin, introducing for the first time the α,β′‐pyridin‐2‐one unit into the macrocyclic frame. Bispalladium(II) di‐p‐pyrirubyrin 6, bispalladium(II) dioxo‐di‐p‐pyrirubyrin 9, and dioxo‐di‐p‐pyrirubyrin 10 absorb and emit light around 1000 nm and are characterized by high photostability. Thus, they are promising candidates for near‐infrared photoacoustic dyes, ideally targeting (9) the wavelength of Yb‐based fiber lasers. The incorporation of an α,β′‐pyridine moiety into expanded porphyrins opens a highly interesting area of research due to the attractive optical and coordination properties of the resulting molecules

Bispalladium(II) Complexes of di‐ p ‐Pyrirubyrin Derivatives as Promising Near‐Infrared Photoacoustic Dyes

The insertion of palladium(II) into di‐p‐pyrirubyrin results in mutually convertible bimetallic complexes. Post‐synthetic functionalization of one of them yielded bispalladium(II) dioxo‐di‐p‐pyrirubyrin and, after demetallation, dioxo‐di‐p‐pyrirubyrin, introducing for the first time the α,β′‐pyridin‐2‐one unit into the macrocyclic frame. Bispalladium(II) di‐p‐pyrirubyrin 6, bispalladium(II) dioxo‐di‐p‐pyrirubyrin 9, and dioxo‐di‐p‐pyrirubyrin 10 absorb and emit light around 1000 nm and are characterized by high photostability. Thus, they are promising candidates for near‐infrared photoacoustic dyes, ideally targeting (9) the wavelength of Yb‐based fiber lasers. The incorporation of an α,β′‐pyridine moiety into expanded porphyrins opens a highly interesting area of research due to the attractive optical and coordination properties of the resulting molecules