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1. Asymmetric Synthesis of P-Stereogenic Secondary Phosphine ­Oxides (SPOs)

   https://doi.org/10.1055/a-1582-0169  

   Glueck, David S. (January 2022, Synthesis)

   Abstract P-Stereogenic secondary phosphine oxides [SPOs, RR′P(O)H], valuable ligands for metal complexes in asymmetric catalysis, are also building blocks for other chiral phosphorus derivatives. This short review summarizes methods used for asymmetric synthesis of P-stereogenic SPOs. 1 Introduction 2 Configurational Stability of P-Stereogenic SPOs 3 Classical Resolution, HPLC Separation, and Dynamic Resolution 4 Synthesis via Chiral Auxiliaries 5 Kinetic Resolution 6 Conclusions and Outlook 

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2. Asymmetric allylic substitution–isomerization to axially chiral enamides via hydrogen-bonding assisted central-to-axial chirality transfer

   https://doi.org/10.1039/D0SC02828B  

   Sun, Chao; Qi, Xiaotian; Min, Xiao-Long; Bai, Xue-Dan; Liu, Peng; He, Ying (September 2020, Chemical Science)

   null (Ed.)

   Axially chiral enamides bearing a N–C axis have been recently studied and were proposed to be valuable chiral building blocks, but a stereoselective synthesis has not been achieved. Here, we report the first enantioselective synthesis of axially chiral enamides via a highly efficient, catalytic approach. In this approach, C(sp 2 )–N bond formation is achieved through an iridium-catalyzed asymmetric allylation, and then in situ isomerization of the initial products through an organic base promoted 1,3-H transfer, leading to the enamide products with excellent central-to-axial transfer of chirality. Computational and experimental studies revealed that the 1,3-H transfer occurs via a stepwise deprotonation/re-protonation pathway with a chiral ion-pair intermediate. Hydrogen bonding interactions with the enamide carbonyl play a significant role in promoting both the reactivity and stereospecificity of the stepwise 1,3-H transfer. The mild and operationally simple formal N -vinylation reaction delivered a series of configurationally stable axially chiral enamides with good to excellent yields and enantioselectivities. 

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3. Enantioseparation and racemization of 3‐fluorooxindoles

   https://doi.org/10.1002/chir.23572  

   Yuan, Andi; Steber, Sarah E.; Xhili, Dea; Nelson, Eryn; Wolf, Christian (May 2023, Chirality)

   Abstract Fluorinated oxindoles are frequently used building blocks in asymmetric synthesis and represent an important scaffold found in a variety of biologically relevant compounds. While it is understood that incorporation of fluorine atoms into organic molecules can improve their pharmacological properties, the impact on the configurational stability of chiral organofluorines is still underexplored. In this study, semipreparative HPLC enantioseparations of five oxindoles were carried out, and the resulting enantiomerically enriched solutions were used to investigate base promoted racemization kinetics at room temperature. It was found that incorporation of fluorine at the chiral center increases the configurational stability, while substitutions on the aromatic ring and at the lactam moiety also have significant effects on the rate of racemization, which generally follows reversible first‐order reaction kinetics. 

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4. Chirality in topologically interlocked material systems

   https://doi.org/10.1016/j.mechmat.2024.104956  

   Kim, Dong Young; Siegmund, Thomas (April 2024, Mechanics of Materials)

   The present study focuses on the mechanical chirality in plate-type topologically interlocked material systems. Topologically interlocked material (TIM) systems are a class of dense architectured materials for which the mechanical response emerges from the elastic behavior of the building blocks and the contact-frictions interactions between the blocks. The resulting mechanical behavior is strongly non-linear due to the stability-instability characteristics of the internal load transfer pattern. Two tessellations are considered (square and hexagonal) and patches from each are used as templates. While individual building blocks are achiral, chirality emerges from the assembly pattern. The measure of \textit{microstructure circulation} is introduced to identify the geometric chirality of TIM systems. TIM systems identified as geometrically chiral are demonstrated to possess mechanical chiral response with a force-torque coupling under transverse mechanical loading of the TIM plate. The chiral length is found to be constant during the elastic response, yet size-dependent. During nonlinear deformation, the chiral length scale increases significantly and again exhibits a strong size dependence. The principle of dissection is introduced to transform non-chiral TIM systems into chiral ones. In the linear deformation regime, the framework of chiral elasticity is shown to be applicable. In the non-linear deformation regime, chirality is found to strongly affect the mechanical behavior more significantly than in the linear regime. Experiments on selected TIM systems validate key findings of the main computational study with the finite element method. 

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5. Crystalline Porous Frameworks via Hierarchical Dynamic Covalent Assembly

   https://doi.org/10.1021/acs.accounts.5c00393  

   Ge, Yanqing; Huang, Shaofeng; Yuan, Zhehao; Zhang, Wei (August 2025, Accounts of Chemical Research)

   Crystalline porous frameworks, such as covalent organic frameworks (COFs), metal–organic frameworks (MOFs), and hydrogen-bonded organic frameworks (HOFs), have demonstrated exceptional potential in diverse applications, including gas adsorption/separation, catalysis, sensing, electronic devices, etc. However, the building blocks for constructing ordered frameworks are typically limited to multisubstituted aromatic small molecules, and uncontrolled interpenetration has remained a long-standing challenge in the field. Shape-persistent macrocycles and molecular cages have garnered significant attention in supramolecular chemistry and materials science due to their unique structures and novel properties. Using such preporous shape-persistent 2D macrocycles or 3D cages as building blocks to construct extended networks is particularly appealing. This macrocycle-to-framework/cage-to-framework hierarchical assembly approach not only mitigates the issue of interpenetration but also enables the integration of diverse properties in an emergent fashion. Since our demonstration of the first organic cage framework (OCF) in 2011 and the first macrocycle-based ionic COFs (ICOFs) in 2015, substantial advancements have been made over the past decade. In this Account, we will summarize our contributions to the development of crystalline porous frameworks, consisting of shape-persistent macrocycles and molecular cages as preporous building blocks, via hierarchical dynamic covalent assembly. We will begin by reviewing representative design strategies and the synthesis of shape-persistent macrocycles and molecular cages from small molecule-based primary building blocks, emphasizing the critical role of dynamic covalent chemistry (DCvC). Next, we will discuss the further assembly of preporous macrocycle/cage-based secondary building blocks into extended frameworks, followed by an overview of their properties and applications. Finally, we will highlight the current challenges and future directions for this hierarchical assembly approach in the synthesis of crystalline porous frameworks. This Account offers valuable insights into the design and synthesis of functional porous frameworks, contributing to the advancement of this important field. 

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