The ruthenium-catalyzed hydroamidation of terminal alkynes has evolved to become a broadly applicable tool for the synthesis of enamides and enimides. Depending on the catalyst system employed, the reaction leads chemo-, regio-, and stereoselectively to a single diastereoisomer. Herein, we present a comprehensive mechanistic study of the ruthenium-catalyzed hydroamidation of terminal alkynes, which includes deuterium-labeling, in situ IR, in situ NMR, and in situ ESI-MS experiments complemented by computational studies. The results support the involvement of ruthenium-hydride and ruthenium-vinylidene species as the key intermediates. They are best explained by a reaction pathway that consists of an oxidative addition of the amide, followed by insertion of a π-coordinated alkyne into a ruthenium-hydride bond, rearrangement to a vinylidene species, nucleophilic attack of the amide, and finally reductive elimination of the product.
A new series of coumarin and benzofuran derivatives were synthesized as potential non-nucleoside reverse transcriptase inhibitors (NNRTIs) by reacting, separately, 4-bromomethylcoumarins, their sulphonyl chlorides, and ethyl 3-(bromomethyl)-6-methoxy-1-benzofuran-2-carboxylate with different imidazoles and their benzo analogs. The antiviral (HIV-1, HIV-2) properties of the newly synthesized compounds were investigated in vitro and all compounds were found to be inactive, except 10 which showed inhibition of HIV-2 with EC50 > 0.51 μgmL−1. The in vitro cytotoxicity of 17 and 19 was assayed against a panel of tumor cell lines consisting of CD4 human T-cells.
Extremely
small, monodisperse, and spheric maghemite (γ-Fe2O3, 2–3 nm) and manganese (4–7 nm),
cobalt (3–5 nm), and zinc ferrite (5–7 nm) nanocrystals
are directly accessible on a large scale starting from inexpensive
metal powders and octanoic acid by thermolysis in a high-boiling solvent.
Bigger particle size is obtainable by prolonged reaction time according
to the Ostwald ripening principle. The superparamagnetic nanocrystals
and their assembly have been characterized by transmission electron
microscopy, powder X-ray diffraction, Mössbauer spectroscopy,
magnetic measurements, and energy-dispersive X-ray spectroscopy.
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