An efficient approach for the synthesis of pyranoquinolines through the indium-catalyzed activation of alkynes is reported. Intramolecular hydroamidation of alkynes can proceed through alkyne activation by indium(III) and then 6-exo-dig cyclization, leading to a fused pyran ring with high selectivity, high atom economy, and good to excellent yields. The cyclization was accomplished through the oxygen, not the nitrogen, of the amide functional group.
An efficient approach for the synthesis of pyrazolopyridines containing the aminochromane motif through a base-catalyzed cyclization reaction is reported. The synthesis was carried out through a three-component reaction of (arylhydrazono)methyl-4H-chromen-4-one, malononitrile, primary amines in the presence of Et3N at room temperature. However, carrying out the reaction under the same conditions without base led to a fused chromanyl-cyanopyridine. High selectivity, high atom economy, and good to high yields in addition to mild reaction conditions are the advantages of this approach.
Currently, the need for research in the field of hemostatic materials seems to be a necessity. The purpose of this study was to prepare and assess a hemostatic polyurethane (PU) sponge containing kaolin (K), tannic acid (TA), and tranexamic acid (TXA) as effective, safe, and inexpensive hemostatic agents. K was incorporated into the sponge (at 4 or 8 wt%, named K4 or K8), also TA (at 1% or 3%, named TA1 or TA3) and TXA (at 300 mg/mL) were added. Four sponges, K4TA1, K4TA3, K8TA1, and K8TA3 were produced and compared via 3‐(4,5‐dimethylthiazol‐2‐yl)‐2,5‐diphenyl tetrazolium bromide assay, fluid uptake, drug release, and blood clotting time/index. K4TA3 was considered optimum and other experiments were continued with this sponge. Scanning electron microscopy results supported that the sponge had a porous structure, and Fourier transform infrared confirmed the corresponding PU spectra and the presence of hemostatic compounds. The hemostatic sponge exhibited a quick initial release of TA and TXA. K4TA3 sponge also exhibited appropriate water uptake. Besides, PU sponges illustrated no cytotoxicity towards human dermal fibroblasts. Furthermore, the sponge presented an antibacterial activity. Hemostatic capability was established in a rat‐tail amputation model bleeding in terms of blood loss and hemostasis time. We also validated the biocompatibility and safety of the materials by hemolysis assessment. This work demonstrated a simple and efficient PU hemostatic sponge that acts via more than one clotting mechanism to control bleeding.
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