Lewis Acid-Promoted Three-Component Cyclization for the Construction of Functionalized Oxazoles.

A simple and efficient synthetic strategy from amides, ynals, and sodium sulfinates via a Lewis acid-promoted three-component reaction has been reported. Thus, a broad range of various aryl (not alkyl)-substituted oxazoles could be synthesized via the formation of C-N, C-O, and C-S bonds in a one-pot process. In addition, this reaction possesses other unique advantages, such as transition metal-free catalysis, high step economy, good functional group tolerance, and good regioselectivity.

Base-Catalyzed One-Pot Synthesis of 2,3,6-Substituted Pyridines.

A three-component reaction catalyzed by base was established, which mainly consisted of ynals, isocyanates, amines and alcohols. This strategy provides a wide range of substrates and represents a simple process for the preparation of different pyridine derivatives in good yields with high regioselectivities.

Precise Control of Radial Catenane Synthesis via Clipping and Pumping.

An unprecedented molecular pumping cassette was designed and implemented for the construction of molecular necklaces, that is, radial [n]catenanes. The mechanism was fully confirmed on a model [2]pseudorotaxane, and the novel clipping-followed-by-pumping strategy was used to prepare a series of [n]catenanes (n = 2-5). A pair of [3]catenane diastereomers sequentially threaded with two different wheels was also accomplished. The success of utilizing molecular pumping to construct molecular necklaces offers new insights into complex molecular architectures and expands the application of molecular machines in synthesis.

Lewis Acid-Catalyzed Synthesis of Polysubstituted Furans from Conjugated Ene-yne-ketones and 1,3,5-Triazinanes.

An efficient and metal-free approach to the construction of diverse functionalized furan derivatives has been developed from ene-yne-ketones and 1,3,5-triazinanes. As an atom-economical and environment-friendly protocol, the new conditions are suitable for selective C-N and C-O bond formation of a wide range of polysubstituted furans in one pot.

Genistein protects against acetaminophen-induced liver toxicity through augmentation of SIRT1 with induction of Nrf2 signalling.

Previous studies suggest that genistein protects liver from acetaminophen (APAP)-induced injury, however, the detailed mechanism of the process is still incompletely. Therefore, present study was to investigate the potential mechanism of the genistein mediated protection against APAP-induced hepatotoxicity. As shown, supplementation with 150 mg/kg genistein greatly alleviated the increase in serum alanine aminotransferase (ALT) activity, aspartate aminotransferase (AST) activity, hepatic malondialdehyde (MDA) contents, and reversed the decrease in hepatic GSH levels in response to overdose APAP. At the same time, hepatic SIRT1 protein and activity were markedly upregulated in mouse receiving genistein. However, the amelioration was almost abolished by the knockdown of hepatic SIRT1 expression using lentivirus carrying specific shRNA targeting SIRT1. These results were further validated by histopathology examination. Moreover, depletion of hepatic SIRT1 prevented the accumulation of Nrf2 in nucleus and the upregulation of the antioxidant gene expression in the presence of genistein and/or APAP. Concomitantly, the induced mRNA expression of UDP-glucuronosyltransferases (UGTs) by genistein was largely dependent on the SIRT1 expression and activity. Together, our results support the notion that the strong elevation of SIRT1 expression and activity may represent a potential mechanism of protection against APAP-induced liver injury by genistein.

Luminescent Metallacycle-Cored Liquid Crystals Induced by Metal Coordination.

Two rhomboidal metallacycles based on metal-coordination-driven self-assembly are presented. Because metal-coordination interactions restrict the rotation of phenyl groups on tetraphenylethene units, these metallacycles were emissive both in solution and in solid state, and their aggregation-induced emission properties were well-retained. Moreover, the rhomboidal metallacyclic structures offer a platform for intermolecular packing beneficial for the formation of liquid crystalline phases. Therefore, although neither of building blocks shows mesogenic properties, both thermotropic and lyotropic (in DMF) mesophases were observed in one of metallacycles, indicating that mesophases could be induced by metal-coordination interactions. This study not only reveals the mechanism for the formation of cavity-cored liquid crystals, but also provides a convenient approach to preparing supramolecular luminescent liquid crystals, which will serve as good candidates for chemo sensors and liquid crystal displays.

A compact chemically driven [2]catenane rotary motor operated through alternate pumping and discharging.

Here we present a compact and precise [2]catenane rotary motor that functions with a single recognition site, capable of achieving a 360° directional rotation powered by chemical fuels. The motor is propelled by an acid-base fueled benzimidazolium pumping cassette and deemed the smallest (molecular weight ∼ 994 Da) catenane rotary motor to date. It can effectively undergo a 180° rotation by transitioning the [24]crown-6 ether (24C6) from the benzimidazolium site to the less favorable alkyl moiety through sequential deprotonation, slipping, and re-protonation operations, generating a meta stable co-conformer. Subsequently, a discharging phase, triggered by de-benzylation and re-benzylation, facilitates the other half-rotation of the motor, returning the 24C6 to its initial position and completing the full directional rotation of the [2]catenane rotary motor within 18 hours. The precision of the motor's operation enables further advances in artificial molecular machines.

A self-assembled M2L2 truncated square and its application as a container for fullerenes.

An unprecedented bisthianthrene dipyridyl ligand was designed and synthesized for coordination driven self-assembly. The combination of this conformationally dynamic linker with a 90° convergent metal corner exclusively afforded a novel M2L2 truncated square-like metallamacrocycle. The single crystal X-ray structure reveals a belt-shaped geometry with a cavity diameter of ca. 13.7 Å. The breathable cavity and electron-rich thianthreno panels enable the highly efficient binding of the fullerenes C60 (Ka = 5.1 × 106 M-1) and C70 (Ka = 3.7 × 106 M-1). The encapsulation of C60 is fully confirmed by NMR, mass spectroscopy and single crystal X-ray diffraction analyses. The cyclic voltammograms further reveal that the truncated square is redox active. The strong binding affinity, adaptive complexation, and redox activity of the thianthrene-incorporated metallamacrocycle provide new insights into the design of supramolecular hosts.

Heteroatom-bridged molecular belts as containers.

Hoop-shaped or belt-like molecules have been fascinating not only due to their challenging synthesis, but also unique physical and chemical properties. The incorporation of heteroatoms (N, O, S, etc.) into these belts could alter both molecular structures and electronic properties which will lead to versatile applications, from advanced host-guest systems to functional materials. Despite numerous computational studies, the synthesis and characterization of heteroatom-bridged double-stranded molecular belts remains scarce. Here we report the synthesis, crystal structure, and host-guest chemistry of two novel heteroatom-bridged belt-like macrocycles composed of phenoxathiin. The bowl-shaped belt demonstrates a strong binding affinity (Ka = 3.6 × 109 M‒2) towards fullerene C60 and forms a 2:1 capsule-like complex with the aid of C‒H···S hydrogen bonds. The column-like belt can bind the cyclic guest [2,2]paracyclophane to form a ring-in-ring complex. The modular synthesis, structural specificity, and diverse host-guest chemistry of cyclophenoxathiins markedly expands the known chemistry of molecular belts.