Highly efficient aqueous phase chemoselective hydrogenation of α,β-unsaturated aldehydes catalysed by phosphine-decorated polymer immobilized IL-stabilized PdNPs

Phosphino-decorated polymer immobilised ionic liquid phase stabilised palladium nanoparticles (PdNP@PPh₂-PIILP) and their PEGylated counterparts (PdNP@PPh₂-PEGPIILP) are remarkably active and exceptionally selective catalysts for the aqueous phase hydrogenation of α,β-unsaturated aldehydes, ketones, esters and nitriles with PdNP@PPh₂-PEGPIILP giving complete conversion and 100% selectivity for reduction of the C=C bond, under mild conditions. This is the most selective PdNP-based system to be reported for the aqueous phase hydrogenation of this class of substrates

Highly efficient and selective aqueous phase hydrogenation of aryl ketones, aldehydes, furfural and levulinic acid and its ethyl ester catalyzed by phosphine oxide-decorated polymer immobilized ionic liquid-stabilized ruthenium nanoparticles

Impregnation of phosphine-decorated styrene-based polymer immobilized ionic liquid (PPh2-PIIL) with ruthenium(III) trichloride resulted in facile reduction of the ruthenium to afford Ru(II)-impregnated phosphine oxide-decorated PIIL (O[double bond, length as m-dash]PPh2PIIL). The derived phosphine oxide-decorated polymer immobilized ionic liquid-stabilized RuNPs (RuNP@O[double bond, length as m-dash]PPh2-PIILS) catalyse the highly efficient and selective aqueous phase reduction of the carbonyl group in aryl and heteroaryl ketones and aldehydes, including furfural, as well as the hydrogenation of levulinic acid and its ethyl ester to afford γ-valerolactone (GVL). While this is the first report of RuNPs stabilized by a phosphine oxide-modified support, there appear to be several recent examples of similar serendipitous oxidations during the synthesis of RuNPs by impregnation of a phosphine-decorated polymer with ruthenium trichloride; as these were either misinterpreted or not recognised as such we have carried out a detailed characterization and evaluation of this system. Reassuringly, RuNP@O[double bond, length as m-dash]PPh2-PIILS generated from phosphine oxide-decorated polymer immobilized ionic liquid (O[double bond, length as m-dash]PPh2-PIIL) impregnated with ruthenium trichloride is as efficient as that prepared directly from RuCl3 and PPh2-PIIL. Incorporation of PEG into the polymer support improved catalyst performance and the initial TOF of 2350 h−1 obtained for the aqueous phase hydrogenation of acetophenone is among the highest to be reported for a ruthenium nanoparticle-based catalyst. Under optimum conditions, RuNP@O[double bond, length as m-dash]PPh2-PEGPIILS recycled ten times with only a minor reduction in activity and no detectable change in selectivity. High yields and excellent selectivities were also obtained for hydrogenation of the C[double bond, length as m-dash]O across a range of substituted aryl and heteroaryl ketones. Complete hydrogenation of the aromatic ring and C[double bond, length as m-dash]O could also be achieved by increasing the pressure and temperature accordingly. The same system also catalyzes the aqueous phase hydrogenation of furfural under mild conditions with an initial TOF of 3160 h−1 as well as the selective hydrogenation of levulinic acid and its ethyl ester to γ-valerolactone (GVL); reaction times for the latter could be reduced quite significantly by addition of either butyric acid or Amberlyst H-15

Orchid re-introductions: an evaluation of success and ecological considerations using key comparative studies from Australia

With global biodiversity in decline, there is now an urgent requirement to take ameliorative action for endangered species in the form of reintroductions. For the highly diverse orchid family, many species face imminent extinction. Successful reintroductions that result in self-sustaining populations require not only an understanding of existing threats, but an in-depth understanding of species ecology. Increasingly, translocations, ranging from re-introductions to assisted colonisation, are being adopted as recovery actions. Do these translocations mitigate threatening processes and account for the two key ecological attributes for orchid survival; pollinator and mycorrhizal presence? Here, we conducted a literature review identifying the known threats to orchid survival and their necessary mitigation strategies. Next, we evaluated the success of 74 published international orchid translocations on 66 species against a consideration of orchid ecological attributes. Lastly, we empirically tested an additional 22 previously unpublished re-introductions on 12 species undertaken since 2007 against a re-introduction process that accounts for identified threats and orchid ecological attributes. We identified habitat destruction, weed invasion, herbivory, illegal collection, pollinator decline, pathogens and climate change as critical threats to orchid survival. In our global review based on published translocations, the average survival rate, 1-year post translocation was 66 % yet only 2.8 % of studies reported natural recruitment in field sites. Although survival of translocated orchids is clearly being achieved, these programmes did not relate orchid growth and development to key ecological requirements of orchid population resilience, pollinator and mycorrhizal ecology. Ensuring pollinator and mycorrhizal presence shows that these two factors alone are key factors influencing survival and persistence in an Australian review of 22 previously unpublished orchid re-introductions. In the Australian review flowering in the year following, out-planting was observed for 81 % of the re-introductions with seed set occurring in 63 % of re-introductions within the length of the study. Recruitment was observed in 18 % of the Australian re-introduced populations indicating a degree of population resilience. As orchid re-introductions will be a major strategy for wild orchid conservation in the future, we present a framework for orchid re-introductions, including criteria for success. We recommend symbiotic propagation and, for specialised pollination syndromes, the study of pollinator interactions prior to site selection and re-introduction of plants