Synthesis and structure of a chiral areno-bridged [2.4]metacyclophane

The reductive coupling reaction of 1,4-bis(3-acetyl-5-tert-butyl-2-methoxyphenyl)butane 3 was carried out using TiCl₄-Zn in pyridine followed by a McMurry coupling reaction to afford the compounds anti and syn 1,2-dimethyl[2.4]MCP-1-ene 4. Bromination of 4 with BTMA-Br₃ in dry CH₂Cl₂ afforded the interesting compound 1,2-bis-(bromomethyl)-5,15-di-tert-butyl-8,18-dimethoxy[2.4]MCP-1-ene 6 and consecutive debromination with Zn and AcOH in CH₂Cl₂ solution afforded the stable solid 5,15-di-tert-butyl-8,18-dimethoxy-1,2-dimethylene[2.4]MCP 7 in 89% yield. Compound 7 was conveniently employed in a Diels–Alder reaction with dimethyl acetylenedicarboxylate (DMAD) to provide 2-(3′,6′-dihydrobenzo)-5,15-di-tert-butyl-8,18-dimethoxy[2.4]MCP-4′,5′-dimethylcarboxylate 8 in good yield. Diels–Alder adduct 8 was converted into a novel and inherently chiral areno-bridged compound [2.4]MCP 9 by aromatization. The chirality of the two conformers was characterized by circular dichroism (CD) spectra of the separated enantiomer which are perfect mirror images of each other.     

Photo-Controllable Rotation of Cholesteric Double-Twist Cylinders

Abstract

We fabricated aggregates of cholesteric cylinders coexisting with the isotropic phase and investigated their dynamics under a temperature gradient. Each constituent cylinder possessed the double-twist (DT) structure, and when a heat flux was applied, the whole aggregates rotated as a rigid-body without changing the DT orientation. The angular velocity was proportional to the heat flux and the rotational direction was determined by the molecular chirality and the flux direction. The result suggests that the rigid-body rotation was driven by the thermomechanical cross-correlation in chiral LCs. We also succeeded in switching the rotation by changing the illumination onto the sample.     

Formation of the serine octamer: Ion evaporation or charge residue

The mechanism of formation for clusters of serine generated by electrospray ionization is hypothesized to play a critical role in determining their ultimate properties. Under carefully manipulated electrospray source conditions, two distinct and well-separated distributions of clusters can be observed. The characteristics of the two cluster populations are consistent with different formation mechanisms, namely ion evaporation and charge residue. Upon further inspection, it is proposed that the magic number intensity, homochiral selectivity, and unique formation of the serine octamer are best explained within the context of the ion evaporation mechanism. As a consequence, solution phase properties of the octamer become important, particularly in relation to interface effects present on the surface of the charged droplet. In contrast, other clusters of serine, including the B form of the octamer, are probably generated by the charge residue mechanism and may have no connection to condensed phase phenomena.     

Synthesis of optically enriched 1,2-aminoalcohols by [2,3]-Wittig rearrangements of 3-aza-allylic alcohol derivatives

[2,3]-Wittig rearrangements of (E)-3-aza-allylic alcohol derivatives can provide access to syn or anti optically enriched 1,2-aminoalcohols by using a chirality transfer or a chiral auxiliary.     

Gold-catalyzed intermolecular hydroalkoxylation of allenes; difference in mechanism between hydroalkoxylation and hydroamination

A wide range of alcohols 2 react with various allenes 1 in the presence of ClAuPPh₃/AgOTf catalyst at ambient temperature without solvent to produce allylic ethers 3. Contrary to the hydroamination, which proceeds through high chiral-face selectivity for chiral allenes to give the corresponding chiral allylic amines, transfer of chirality is not observed in the hydroalkoxylation, suggesting that the mechanism of the gold-catalyzed hydroalkoxylation is different from that of hydroamination.     

Comprehensive H2O Molecules Regulation via Deep Eutectic Solvents for Ultra-Stable Zinc Metal Anode

The corrosion, parasitic reactions, and aggravated dendrite growth severely restrict development of aqueous Zn metal batteries. Here, we report a novel strategy to break the hydrogen bond network between water molecules and construct the Zn(TFSI)₂-sulfolane-H₂O deep eutectic solvents. This strategy cuts off the transfer of protons/hydroxides and inhibits the activity of H₂O, as reflected in a much lower freezing point (<−80 °C), a significantly larger electrochemical stable window (>3 V), and suppressed evaporative water from electrolytes. Stable Zn plating/stripping for over 9600 h was obtained. Based on experimental characterizations and theoretical simulations, it has been proved that sulfolane can effectively regulate solvation shell and simultaneously build the multifunctional Zn-electrolyte interface. Moreover, the multi-layer homemade modular cell and 1.32 Ah pouch cell further confirm its prospect for practical application.     

Optochemical Control of mRNA Translation in Eukaryotes

A major stage in the expression of genes is the translation of messenger RNA (mRNA), and the regulation of this process is essential for protein production in cells. How tightly controlled gene expression can be spatially and temporally, is particularly evident in polar cells and embryonic development. We need tools to dissect these complex processes, if we wish to understand the underlying links, especially the difficulties brought on by malfunction. External bioorthogonal triggers are very helpful in this area, if they let us precisely control where and when a process is started. Equipping nucleic acids with light-responsive groups has proven to be an effective approach to examine the dynamic regulatory route of mRNA translation in living cells. In this review, we present an overview of the most recent methods for optochemically controlling translation, focusing on cis-acting technologies.     

Combining Imine Condensation Chemistry with [3,3] Diaza-Cope Rearrangement for One-Step Formation of Hydrolytically Stable Chiral Architectures

Dynamic covalent chemistry (DCC) has, in recent years, provided valuable tools to synthesize molecular architectures of increasing complexity. We have also taken advantage of imine DCC chemistry to prepare TPMA -based supramolecular cages for molecular recognition applications. However, the versatility of this approach has as a major drawback the intrinsic hydrolytic lability of imines, which hampers some applications. We present herein a synthetic strategy that combines the advantages of a thermodynamic-driven formation of a supramolecular structure using imine chemistry, together with the possibility to synthetize chiral hydrolytically stable structures through a [3,3]-sigmatropic rearrangement. A preliminary mechanistic analysis of this one-pot synthesis and the scope of the reaction are also discussed.     

Dynamic Kinetic Resolution of 2-(Quinolin-8-yl)Benzaldehydes: Atroposelective Iridium-Catalyzed Transfer Hydrogenative Allylation

An atroposelective Ir-catalyzed dynamic kinetic resolution (DKR) of 2-(quinolin-8-yl)benzaldehydes/1-naphthaldehydes by transfer hydrogenative coupling of allyl acetate is disclosed. The allylation reaction takes place with simultaneous installation of central and axial chirality, reaching high diastereoselectivities and excellent enantiomeric excesses when ortho-cyclometalated iridium-DM-BINAP is used as the catalyst. The racemization of the substrates occurs through a designed transient Lewis acid-base interaction between the quinoline nitrogen atom and the aldehyde carbonyl group.     

Chiroptical Amplification of Induced Circularly Polarized Luminescence in Nucleotide-Templated Supramolecular Polymer

Efficient circularly polarized luminescence (CPL) from purely organic molecules holds great promise for applications in displays, sensing, and bioimaging. However, achieving high dissymmetry values (g_lum) from organic chromophores remains a significant challenge. Herein, we present a bioinspired approach using adenosine triphosphate (ATP)-triggered supramolecular polymerization of a naphthalene diimide-derived monomer ( ANSG ) to induce CPL with a remarkable g_lum value of 1.1×10⁻². The ANSG molecules undergo a templated, chiral self-assembly through a cooperative growth mechanism in the presence of ATP, resulting in scrolled nanotubes with aggregation-induced enhanced emission (AIEE) and induced CPL. Furthermore, we demonstrate the concept of chiroptical amplification of induced CPL by efficiently amplifying asymmetry using a mixture of chiral ATP and achiral pyrophosphate. This innovative approach opens numerous opportunities in the emerging field of circularly polarized luminescence.