Herein, we report a heterogeneous TiO -supported Re catalyst (Re/TiO ) that promotes various selective hydrogenation reactions, which includes the hydrogenation of esters to alcohols, the hydrogenation of amides to amines, and the N-methylation of amines, by using H and CO . Initially, Re/TiO was evaluated in the context of the selective hydrogenation of 3-phenylpropionic acid methyl ester to afford 3-phenylpropanol (pH2 =5 MPa, T=180 °C), which revealed a superior performance over other catalysts that we tested in this study. In contrast to other typical heterogeneous catalysts, hydrogenation reactions with Re/TiO did not produce dearomatized byproducts. DFT studies suggested that the high selectivity for the formation of alcohols in favor of the hydrogenation of aromatic rings is ascribed to the higher affinity of Re towards the COOCH group than to the benzene ring. Moreover, Re/TiO showed a wide substrate scope for the hydrogenation reaction (19 examples). Subsequently, this Re/TiO catalyst was applied to the hydrogenation of amides, the N-methylation of amines, and the N-alkylation of amines with carboxylic acids or esters.
TiO2-supported Re, Re/TiO2, was found to promote selective hydrogenation of carboxylic acids having aromatic and aliphatic moieties to the corresponding alcohols. Re/TiO2 showed superior results compared to other transition-metal-loaded TiO2 and supported Re catalysts for selective hydrogenation of 3-phenylpropionic acid. 3phenylpropanol was produced in 97% yield under mild conditions (5 MPa H-2 at 140 degrees C). Contrary to typical heterogeneous catalysts, Re/TiO2 does not lead to the formation of dearomatized byproducts. The catalyst is recyclable and shows a wide substrate scope in the synthesis of alcohols (22 examples; up to 97% isolated yield)
Insects and fungi share a long history of association in various habitats, including the wood-decomposition niche. Fungal mimicry of termite eggs is one of the most striking evolutionary consequences of insect-fungus association. Termites of the genus Reticulitermes often harbor fungal sclerotia, called "termite balls," along with eggs in nursery chambers, whereby the fungus gains a competitor-free habitat in termite nests. Sophisticated morphological and chemical camouflage are needed for the fungus to mimic termite eggs. However, the mechanism of chemical egg mimicry by the fungus is unknown. Here, we show that the fungus mimics termite eggs chemically by producing the cellulose-digesting enzyme beta-glucosidase. We found that the termite egg-recognition pheromone consists of beta-glucosidase and lysozyme. Both enzymes are major salivary compounds in termites and are also produced in termite eggs. Termite balls were tended by termites only when the fungus produced beta-glucosidase. Our results demonstrated that the overlap of the cellulose digestion niche between termites and the fungus sharing the same chemicals provided the opportunity for the origin of termite egg mimicry by the fungus. This suggests that pheromone compounds might have originally evolved within other life history contexts, only later gaining function in chemical communication.
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