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    ABSTRACT: A rapid and diastereoselective synthesis of highly substituted aminobicyclo[4.3.0]nonanes and bicyclo [4.4.0]decanes from alkyne derived allylic alcohols has been developed using a one-pot multi-bond forming tandem catalytic process. Overman rearrangement of the allylic trichloroacetimidates was followed by a ring closing enyne metathesis/cross metathesis sequence of reactions, in which both steps were catalysed by Grubbs second generation catalyst. The resulting exo-diene was then subjected to a hydrogen bonding directed Diels-Alder reaction forming an endo-adduct as a single diastereomer. Variation of the cross metathesis partner and dienophile allowed examination of the scope of this one-pot process and the preparation of a diverse series of highly substituted polycyclic scaffolds.
    No preview · Article · Oct 2014 · Tetrahedron
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    ABSTRACT: The hydrogenation of 4-nitroacetophenone (4-NAP) and 4-aminoacetophenone (4-AAP) was examined over rhodium/silica catalysts. The reactions were carried out using isopropanol as the solvent under a range of temperatures (303-333 K) and pressures (1-5 barg). An activation energy of 50 +/- 14 mol(-1) was determined for 4-NAP hydrogenation and 48 +/- 2 kJ mol(-1) for 4-AAP hydrogenation. Orders of reaction were obtained for 4-NAP (zero order) and hydrogen (first order) and a kinetic isotope effect of 3.0 was observed for 4-NAP hydrogenation and similar to 1.4 for 4-AAP hydrogenation when deuterium was used. Under specific conditions high yields (similar to 94%) to 4-aminoacetophenone and 1-(4-aminophenyl) ethanol could be obtained from 4-NAP hydrogenation. An antipathetic metal crystallite particle size effect was observed for both reactants.
    No preview · Article · Aug 2014 · Applied Catalysis A General
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    ABSTRACT: A two-step process combining percolation-mode ammonia pretreatment of poplar sawdust with mild organosolv purification of the extracted lignin produced high quality, high purity lignin in up to 31% yield and 50% recovery. The uncondensed fraction of the isolated lignin was up to 34%, close to that the native lignin (40%). Less lignin was recovered after pretreatment in batch mode, apparently due to condensation during the longer residence time of the solubilised lignin at elevated temperature. The lignin recovery was directly correlated with its molecular weight and its nitrogen content. Low nitrogen incorporation, observed at high ammonia concentration, may be explained by limited homolytic cleavage of β-O-4 bonds. Ammonia concentrations from 15% to 25% (w/w) gave similar results in terms of lignin structure, yield and recovery.
    No preview · Article · Jan 2014 · Bioresource Technology
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