Dehydrative alkynylation of 3-hydroxyisoindolinones with terminal alkynes for the synthesis of 3-alkynylated 3,3-disubstituted isoindolinones.

A brand-new procedure for the synthesis of 3-alkynylated 3,3-disubstituted isoindolinones has been disclosed via a HOTf or Fe(OTf)3-catalyzed dehydrative alkynylation of 3-hydroxyisoindolinones with terminal alkynes. Aryl, alkenyl and alkyl terminal alkynes are suitable to couple with a broad range of 3-hydroxyisoindolinones to afford the desired products in moderate to good yields. This protocol features the use of an inexpensive catalyst, mild reaction conditions, broad substrate scope and easy elaboration of the products.

Enantioselective Ir-Catalyzed Allyl Alkylation/Semipinacol Rearrangement.

The semipinacol rearrangement is a powerful and versatile method for constructing all-carbon quaternary stereocenters. The development of catalytic asymmetric semipinacol rearrangements using multifunctionalizable electrophiles remains highly sought-after in organic synthesis. In this study, a catalytic enantioselective allylic cation-induced semipinacol rearrangement reaction was presented that enables the simultaneous construction of two skipped chiral carbon centers. Chiral Ir(I)-(P,olefin) and Sc(OTf)3 catalysts cooperatively initiate the asymmetric allylic alkylation of alkenyl cyclobutanols with allylic alcohols, triggering ring expansion of the cyclobutanol moiety through a stereoselective 1,2-alkyl migration. The reaction afforded a range of cyclopentanones bearing an α-quaternary carbon that is adjacent to a chiral allyl scaffold. The products were applied to synthesize enantioenriched fused tricyclopentanoids bearing four stereogenic carbon centers.

Tandem phospha-Michael addition/cyclization/dehydration of 2-hydroxychalcones with H-phosphine oxides for the synthesis of 4-phosphorylated 4H-chromenes.

A Hg(OTf)2-catalyzed tandem phospha-Michael addition/cyclization/dehydration of 2-hydroxychalcones with H-phosphine oxides is presented. This protocol provides a new and supplementary approach for the preparation of 4-phosphorylated 4H-chromenes in good yields (up to 99%). In addition, this domino reaction allows the successful construction of two new C-P and C-O bonds in a one-pot operation.

Nickel-Catalyzed Reductive Cross-Coupling of Aziridines and Allylic Chlorides.

A nickel-catalyzed reductive cross-coupling of aziridines and allylic chlorides was realized by using manganese metal as the reducing agent. This protocol afforded a convenient approach to obtain ß-allyl-substituted arylethylamines bearing various functional groups. The utility of this reaction was also demonstrated by scale-up preparation and diverse transformations, including the synthesis of Baclofen and several bioactive molecular motifs.

Anti-freezing dual-network hydrogels with high-strength, self-adhesive and strain-sensitive for flexible sensors.

Hydrogels as flexible sensor have attracted significant attention due to its conductivity, stretchability and flexibility. However, it is still a great challenge to prepare hydrogels that simultaneously possess high strength, anti-fatigue, self-adhesion, and anti-freezing. Herein, a multifunctional dual-network hydrogel was prepared by in situ polymerization of acrylic monomer in chitosan chains, and coordinated with aluminum chloride and glycerol. Based on chain entanglement, hydrogen bonding and coordination interactions, this dual-network hydrogel exhibited excellent mechanical properties, good fatigue resistance, and excellent adhesion performance. It can be used as a strain sensor for its stable conductivity and high sensitivity, which could monitor both large human motions and subtle motions. Due to the presence of glycerol, the hydrogel showed outstanding freezing resistance and still kept flexible and conductive even at low temperatures (-20 °C). This hydrogel can be applied as a flexible wearable sensor for monitoring human motion in extreme low-temperature condition.

Modular Synthesis of Enantioenriched α-Chiral Homoallylic Amidines Enabled by Relay Ir/Cu Catalysis.

The cascade of Ir-catalyzed enantioselective allylic amination and Cu-catalyzed alkyne-azide cycloaddition was designed for the asymmetric synthesis of homoallylic amidines. The nucleophilic addition of an in situ-generated enantioenriched tertiary allylamine to a ketenimine intermediate triggers a rapid and stereospecific zwitterionic aza-Claisen rearrangement in a 1,3-chiral transfer manner. The approach allows modular access to enantioenriched α-chiral homoallylic amidines in high yields with a high level of enantiomeric purity.

Nickel-Catalyzed Three-Component Cross-Electrophile Coupling of 1,3-Dienes with Aldehydes and Aryl Bromides.

We herein report a Ni-catalyzed three-component cross-electrophile coupling of 1,3-dienes with aldehydes and aryl bromides using manganese metal as the reducing agent. This efficient protocol accomplishes dicarbofunctionalization of 1,3-dienes to synthesize diverse structural 1,4-disubstituted homoallylic alcohols by forming two new C-C bonds in one time. Mechanistic study suggests that an allyl-nickel(I) species is involved in the catalytic cycle.

Pd-Catalyzed Enantioselective (3+2)-Cycloaddition of Vinyl-Substituted Oxyallyl Carbonates with Isocyanates and Ketones.

The vinyl-substituted oxyallyl carbonates were exploited as a new C,O-dipole for enantioselective Pd-catalyzed (3+2) cycloaddition. The corresponding oxyallyl-Pd species was weakly nucleophilic to react with activated carbonyl compounds, affording multisubstituted and enantioenriched oxazolidinones and 1,3-dioxolanes with a high degree of chemo- and stereoselectivity. The synthetic transformations of oxazolidinone product were carried out to build enantioenriched α-chiral aminoketone and epoxy derivatives.

Arylboronic Acid Catalyzed Dehydrative Mono-/Dialkylation Reactions of ß-Ketoacids and Alcohols.

The dehydrative mono-/dialkylation reactions of alcohols and ß-ketoacids were realized under arylboronic acid catalysis, furnishing a series of ß-aryl ketones and ß-ketoesters in yields of 15-99%, with CO2 and H2O being the byproducts. In this context, the decarboxylative alkylation reaction occurred to give ß-aryl ketones at 50 °C, while the decarboxylation was suppressed to generate dialkylated ester products at 0 °C. A possible catalytic cycle was proposed based on control experiments.

Biased Symmetry Breaking and Chiral Control by Self-Replicating in Achiral Tetradentate Platinum (II) Complexes.

Obtaining homochirality from biased symmetry-breaking of self-assembly in achiral molecules remains a great challenge due to the lack of ingenious strategies and controlling their handedness. Here, we report the first case of biased symmetry breaking from achiral platinum (II) liquid crystals which self-organize into an enantiomerically enriched single domain without selection of handedness in twist grain boundary TGB [ *] phase. Most importantly, the chiral control of self-organization can be achieved by using above the homochiral liquid crystal films with determined handedness (P or M) as a template. Moreover, benefiting from self-assembled superhelix, these complexes exhibit prominent circularly polarized luminescence with high |glum | up to 3.4×10-3 in the TGB [ *] mesophase. This work paves a neoteric avenue for the development of chiral self-assemblies from achiral molecules.

Nickel-Catalyzed Carboalkenylation of 1,3-Dienes with Aldehydes and Alkenylzirconium Reagents: Access to Skipped Dienes.

A regio- and stereoselective nickel-catalyzed three-component coupling reaction of aldehydes, 1,3-dienes, and alkenylzirconium reagents was realized. The ligand- and additive-free protocol afforded a convenient approach to the synthesis of skipped diene compounds bearing various functionals (e.g., hydroxyl, carbonyl, halide) and heterocyclic groups. The products were readily transformed into structurally diverse polyenes. The utility of this reaction was also demonstrated by the one-pot operation and scale-up preparation.

Highly Enantioselective Iridium-Catalyzed Coupling Reaction of Vinyl Azides and Racemic Allylic Carbonates.

The iridium-catalyzed enantioselective coupling reaction of vinyl azides and allylic electrophiles is presented and provides access to ß-chiral carbonyl derivatives. Vinyl azides are used as acetamide enolate or acetonitrile carbanion surrogates, leading to γ,δ-unsaturated ß-substituted amides as well as nitriles with excellent enantiomeric excess. These products are readily transformed into chiral N-containing building blocks and pharmaceuticals. A mechanism is proposed to rationalize the chemoselectivity of this coupling reaction.

Copper(I)-Catalyzed Ketenimine Formation/Aza-Claisen Rearrangement Cascade for Stereoselective Synthesis of α-Allylic Amidines.

A copper-catalyzed three-component reaction of terminal alkynes, TsN3, and tertiary allylic amines is developed toward the one-pot synthesis of α-allylic amidines. The product was synthesized on gram scale under 1 mol % of catalyst loading. Transformations of products into alkenyl amine and other nitrogen-containing compounds are demonstrated without any loss of stereochemical information.

Columnar Iridium(III) Metallomesogens Based on Polycatenar Pyridyltetrazolate with Ambipolar Carrier Mobility Behavior.

In this paper, we have designed and synthesized a series of neutral liquid-crystalline iridium(III) complexes based on polycatenar 2,5-diphenylpyridine and pyridyltetrazolate derivatives. Iridium(III) complexes all display highly emissive behavior with photoluminescence quantum yields in the range of 0.45-0.66 and a maximum emission wavelength at ∼563 nm. Hexagonal columnar mesophases of iridium(III) complexes can be obtained by changing the number and length of peripheral alkoxyl chains attached to a 2,5-diphenylpyridine ligand (main ligand) and a pyridyltetrazolate ligand (auxiliary ligand). Moreover, experimental results of the charge transport properties for these iridium(III) complexes, which were measured by the space charge limited-current method, exhibit ambipolar carrier mobility behavior. In particular, the liquid-crystalline iridium(III) complexes can self-organize into one-dimensional (1D) nanostructure after thermal annealing treatment in their liquid-crystalline phase. The devices based on liquid crystal film display improved charge transport behavior compared with that of the devices based on polycrystalline film, indicating 1D nanostructure is beneficial to charge carrier injection and transportation.

New phosphorescent platinum(ii) complexes with tetradentate C*N

New phosphorescent, liquid crystalline cyclometalated tetradentate platinum complexes (Pt-L16, Pt-L12 and Pt-L6) based on the tetradentate C*N^N*C ligands (C*N^N*C = 6,6'-bis(4-(alkoxy)-phenoxy)-2,2'-bipyridine) are designed and synthesized. Their crystal structure, and photophysical, electrochemical and liquid crystal characteristics were investigated. The X-ray structure of Pt-L12 shows a severe distortion of this complex towards a tetrahedral geometry. All complexes are emissive both in degassed solution and in the solid state at room temperature with emission maxima in the red region of the spectrum. Pt-L16 and Pt-L12 show monotropic smectic liquid crystal characteristics. Moreover, these liquid crystal complexes can be aligned on a rubbed nylon-6 glass substrate and produce polarized emission with a dichroic ratio of 5.1.