An S-shaped double azahelicene (1) was synthesized in excellent yield by a palladium-catalyzed double dehydrogenative C-H coupling reaction. The stereochemistry of 1 was confirmed to be dl by single-crystal X-ray diffraction analysis. Selective formation of dl-1 was attributed to the isomerization of the kinetically controlled product (meso-1) into the more thermodynamically stable dl-1 under the applied reaction conditions. dl-1 can coordinate to palladium(II) in a bidentate trans-chelating fashion, which was confirmed by X-ray absorption fine structure (XAFS) as well as by X-ray photoelectron spectroscopy (XPS), diffuse reflectance (DR) UV/Vis, and far-infrared (FIR) absorption spectroscopy. Theoretical calculations of palladium complex 16 revealed a weak attractive interaction between palladium and carbon atoms on the central dimethoxynaphthalene core, which could facilitate a disproportionation between a trans-chelating (dl-1)⋅PdCl complex and PdCl to form 16.
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http://dx.doi.org/10.1002/chem.202002405 | DOI Listing |
J Clin Med
January 2025
Interventional Radiology Department, Adana Dr. Turgut Noyan Application and Research Center, Başkent University, 01250 Adana, Turkey.
: The objective of the current research is to assess the benefits that come with antegrade ureteral stenting coupled with imaging techniques in children and also provide a new classification based on the ureter's morphological elements. : Between 2011 and 2024, 107 antegrade stent placement procedures performed in 71 pediatric patients aged 0-12 years who could not undergo retrograde double-J stent placement were retrospectively analyzed. According to the morphologic structure of the ureter, four categories were classified as normal, straight/slightly angled, S-shaped, and spiral-shaped.
View Article and Find Full Text PDFNat Commun
January 2025
Chongqing Key Laboratory of Natural Product Synthesis and Drug Research, Chemical Biology Research Center, School of Pharmaceutical Sciences, Chongqing University, Chongqing, China.
Helicene-shaped molecules are compelling chemical structures with unique twisted helical chirality and remarkable properties. Although progress occurs in the catalytic asymmetric synthesis of helicene (-like) molecules, the enantioselective synthesis of multiple helicenes, especially four or higher helicity, is still challenging and has yet to be achieved. Herein, we report an organocatalytic [4 + 2] cycloadditions to achieve double S-shaped quadruple helicene-like molecules with high enantioselectivity (up to 96% e.
View Article and Find Full Text PDFJ Endod
December 2024
Division of Endodontology, Department of Conservative and Preventive Dentistry, Center for Dental Medicine, University of Zurich, Zurich, Switzerland. Electronic address:
Introduction: Adding a compatible chelator to the sodium hypochlorite (NaOCl) solution applied during instrumentation may affect shaping efficacy and canal transportation. This was studied in simulated double-curved root canals.
Methods: High-precision computer numerical control milling was used to recreate standardized S-shaped canals from a resin training block in longitudinally sectioned bovine incisor roots.
Ann Afr Med
October 2024
Department of Anatomy, Manipal University College Malaysia, Malacca, Malaysia.
Background: Anatomical and developmental variations of ureters and renal pelvis have been observed frequently during routine human cadaveric dissection and surgical practice; however, their coexistence with accessory or aberrant renal arteries is exceptionally rare. Accordingly, this study was designed to evaluate the prevalence of anatomical and developmental abnormalities of ureters and renal pelvis existing with accessory renal arteries in human cadavers.
Materials And Methods: This study was carried out on 50 human cadavers including dissected specimens (25 males and 25 females) the kidneys, renal pelvis, and ureters along with their arteries were exposed and the anomalous abnormalities of the renal pelvis and ureters existing with accessory renal arteries were observed.
Tree Physiol
October 2024
College of Forestry, Northwest A&F University, Tai Cheng Road No. 3, Yangling, Shaanxi 712100, China.
In addition to inducing xylem embolism, freeze-thaw events can cause frost fatigue phenomena. Freezing temperature, freezing times, number of freeze-thaw cycles and frost drought can affect the level of freeze-thaw-induced embolism, but it is unknown whether there is an effect on frost fatigue. We assessed whether these frost-related factors changed frost fatigue in the three diffuse-porous species by simulating freeze-thaw treatments under different conditions.
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