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Three-dimensional alicyclic skeletons with multiple stereochemically defined chiral centers are highly valuable in modern drug discovery. Here, we reported a diverse approach to access 1,2- and 1,3-disubstituted chiral cycloalkanes by the strategy of NiH-catalyzed, transannular-directed alkene desymmetrization. The ring strain of the bridged bicyclic organonickel intermediate and the coordination effect of the ligand were identified as crucial factors in determining site selectivity by influencing the NiH migration step. This methodology demonstrates a broad substrate scope and displays good tolerance toward various functional groups, resulting in excellent outcomes in terms of the yield, regioselectivity, and enantioselectivity.
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http://dx.doi.org/10.1021/acs.orglett.4c02975 | DOI Listing |
J Am Chem Soc
May 2022
Univ Rennes, CNRS, ISCR (Institut des Sciences Chimiques de Rennes) - UMR 6226, F-35000 Rennes, France.
We report on the synthesis and self-assembly of 2,15- and 4,13-disubstituted carbo[6]helicenes and bearing 3,4,5-tridodecyloxybenzamide groups. The self-assembly of these [6]helicenes is strongly influenced by the substitution pattern in the helicene core that affects the mutual orientation of the monomeric units in the aggregated form. Thus, the 2,15-substituted derivative undergoes an isodesmic supramolecular polymerization forming globular nanoparticles that maintain circularly polarized light (CPL) with values as high as 2 × 10.
View Article and Find Full Text PDFAngew Chem Int Ed Engl
February 2022
Institut für Organische und Biomolekulare Chemie, Georg-August-Universität Göttingen, Tammannstrasse 2, 37073, Göttingen, Germany.
A highly enantioselective synthesis of 5,13-disubstituted dibenzo[d,d']benzo[1,2-b:4,3-b']dithiophenes is reported. Key for the successful assembly of these helical architectures is the last two successive Au-catalyzed intramolecular alkyne hydroarylation events. Specifically, the second cyclization is the enantiodetermining step of the whole process and provides the desired helicenes with excellent ee values when a TADDOL-derived 1,2,3-(triazolium)phosphonite moiety (TADDOL: α,α,α',α'-tetraaryl-1,3-dioxolane-4,5-dimethanol) is employed as an ancillary ligand.
View Article and Find Full Text PDFInorg Chem
December 2014
Department of Chemistry, Indian Institute of Technology Roorkee, Roorkee - 247667, India.
Two new families of porphyrins with mixed substituent pattern, viz. 2-nitro-12,13-disubstituted-meso-tetraphenylporphyrins (H2TPP(NO2)X2, X = Ph, phenylethynyl (PE), 2-thienyl (Th), Br, and CN) and 2-nitro-7,8,12,13,17,18-hexasubstituted-meso-tetraphenylporphyrins (H2TPP(NO2)X6, X = Br, Ph, PE, and Th), and their metal (Co(II), Ni(II), Cu(II), and Zn(II)) complexes have been synthesized and characterized. H2TPP(NO2)X6 exhibited remarkable red shift in the Soret band (45-70 nm) and longest wavelength band, Qx(0,0) (65-90 nm), as compared to H2TPP(NO2).
View Article and Find Full Text PDFPhotochem Photobiol Sci
December 2008
Bell Laboratories, Murray Hill, NJ 07974, USA.
Computational and experimental studies have been performed to investigate the photostability of a series of 6,13-bis(arylalkynyl)-substituted pentacenes in the presence of oxygen. These studies indicate that photostabilization occurs through a selective LUMO orbital stabilization as has been seen previously for 6,13-bis(triisopropylsilylethynyl)pentacene. Marcus theory analysis suggests that the difference in vibrational reorganization energies across all compounds is small and that the thermodynamic driving force for forward electron transfer is primarily responsible for the observed photostabilization.
View Article and Find Full Text PDFJ Org Chem
November 2003
Department of Chemistry, School of Science and Engineering, Waseda University, Shinjuku-ku, Tokyo 169-8555, Japan.