The adsorption and self-organization of racemic mixture of 8-nitrospiropyran (SP8) molecules on Au(111) surfaces was studied by scanning tunneling microscopy (STM) in ultrahigh vacuum (UHV). The SP8 enantiomers, in spite of their low-symmetric and nonplanar molecular structures, formed well-ordered monolayers on Au(111). In the monolayers, we found two types of enantiomorphous, i.e., mirror-imaged, 2D chiral domains, denoted as lambda and delta phases. Both phases consist of periodically packed chiral quatrefoils. In the lambda domain, the quatrefoils are counterclockwise folded, while in the delta domain, the quatrefoils are clockwise folded. High-resolution STM images revealed that each chiral quatrefoil contains four heterochiral dimers and that each dimer is composed of two antiparallelly packed homochiral SP8 molecules. Therefore both of the two mirror-imaged 2D chiral structures are not chirally pure but racemic 2D crystals. A domain boundary, which serves as the glide reflection line between a lambda domain and a delta domain, was also observed along the [11] direction of the Au(111) substrate.
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Inorg Chem
January 2025
Henan Provincial Key Laboratory of Surface and Interface Science, Zhengzhou University of Light Industry, Zhengzhou 450002, P. R. China.
Three two-dimensional (2D) chiral Ag(I) complexes with formulas [Ag(L)(5-nipa)] (), [Ag(L)(5-nipa)] (), and {[Ag(L)(5-hipa)]·2HO} () were prepared through the reactions of AgO with enantiopure -monodentate N-donors (L/L) and different dicarboxylic acids bearing A (acceptor)-π-- and D (donor)-π--type structural features, where / = (-)/(+)-2-(4'-pyridyl)-4,5-pinene-pyridine, 5-Hnipa = 5-nitroisophthalic acid, and 5-Hhipa = 5-hydroxyisophthalic acid. A study of their nonlinear optical responses reveals that chiral and enantiomeric pairs with the A-π--type dicarboxylic acid ligand simultaneously display second- and third-harmonic generation (SHG and THG) responses, while chiral containing the D-π--type dicarboxylic acid ligand only exhibits a very strong THG response. The THG intensity of is 451 × α-SiO, being about 27 and 24 times larger than those of and , respectively.
View Article and Find Full Text PDFAngew Chem Int Ed Engl
January 2025
Dalian University of Technology, School of Chemical Engineering, No 2 Linggong Road,Ganjingzi District, 116024, Dalian, CHINA.
The Pd-catalyzed asymmetric hydrogenolysis rearrangement of allylic acetates using (s-Bu)3BHK has been described, achieving the synthesis of axially chiral alkylidene cycloalkanes with excellent enantioselectivities (up to 99% ee) and a wide substrate scope (30 examples of cyclohexanes and cyclobutanes). To the best of our knowledge, this is the first time to achieve synthesis of axially chiral olefins via asymmetric hydrogenolysis of allylic acetates. This methodology not only offers a novel synthetic pathway for non-atropisomeric axially chiral structures but also highlights the potential of asymmetric hydrogenolysis as a powerful tool in synthetic organic chemistry.
View Article and Find Full Text PDFChembiochem
January 2025
University of Pittsburgh, Department of Chemistry, 219 Parkman Ave., 15260, Pittsburgh, UNITED STATES OF AMERICA.
The α-helix is an abundant and functionally important element of protein secondary structure, which has motivated intensive efforts toward chemical strategies to stabilize helical folds. One such method is the incorporation of non-canonical backbone composition through an additional methyl substituent at the Cα atom. Examples of monomers include the achiral 2-aminoisobutyric acid (Aib) with geminal dimethyl substitution and chiral analogues with one methyl and one non-methyl substituent.
View Article and Find Full Text PDFOrg Lett
January 2025
Key Laboratory of Organic Synthesis of Jiangsu Province, College of Chemistry, Chemical Engineering and Materials Science & Collaborative Innovation Center of Suzhou Nano Science and Technology, Soochow University, Suzhou 215123, P. R. China.
The azahelicenes are structurally fascinating and practically useful chiral scaffolds, but their synthesis, especially in a catalytically asymmetric manner, is rather challenging. Herein, we report a CPA-catalyzed transfer hydrogenation process, which enables a rapid kinetic resolution of aza[6]helicenes. The established strategy provides facile access to enantioenriched aza[6]helicenes and tetrahydro[6]helicenes from easily available starting materials.
View Article and Find Full Text PDFJ Am Chem Soc
January 2025
Key Laboratory of Applied Chemistry of Chongqing Municipality and Chongqing Key Laboratory of Soft-Matter Material Chemistry and Function Manufacturing, School of Chemistry and Chemical Engineering, Southwest University, Chongqing 400715, China.
Achieving catalytic asymmetric functionalization of methylenecyclopropanes (MCPs) by selective C-C bond cleavage is a notable challenge due to the intricate reaction partners involved. In this work, we report that chiral aldehyde/palladium combined catalysis enables the asymmetric functionalization of MCPs with NH-unprotected amino acid esters. This reaction proceeds through a regiospecific branched ring-opening mechanism, resulting in optically active α,α-disubstituted α-amino acid esters bearing nonconjugated terminal alkene units.
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