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We disclose a new Brønsted acid promoted quinoline synthesis, proceeding via homo‐diaza‐Cope rearrangement of N‐aryl‐N’‐cyclopropyl hydrazines. Our strategy can be considered a homologation of Fischer’s classical indol synthesis and delivers 6‐membered N‐heterocycles, including previously inaccessible pyridine derivatives. The approach can also be used as a pyridiannulation methodology toward constructing polycyclic polyheteroaromatics. A computational analysis has been employed to probe plausible activation modes and to interrogate the role of the catalyst.
By performing icing experiments on hydrophilic and hydrophobic surfaces of pyroelectric amino acids and on the x‐cut faces of LiTaO 3 , we discovered that the effect of electrofreezing of super cooled water is triggered by ions of carbonic acid. During the cooling of the hydrophilic pyroelectric crystals, a continuous water layer is created between the charged hemihedral faces, as confirmed by impedance measurements. As a result, a current of carbonic acid ions, produced by dissolved environmental CO 2 , flows through the wetted layer towards the hemihedral faces and elevates the icing temperature. This proposed mechanism is based on the following: (i) on hydrophilic surfaces, water with dissolved CO 2 (pH 4) freezes at higher temperatures
Resolving interstitial hydrogen atoms at the surfaces and interfaces is crucial for understanding the mechanical and physicochemical properties of metal hydrides. Although palladium (Pd) hydrides hold important applications in hydrogen storage and electrocatalysis, the atomic position of interstitial hydrogen at Pd hydride near surfaces still remains undetermined. We report here the first direct imaging of subsurface hydrogen atoms absorbed in Pd nanoparticles by using differentiated and integrated differential phase contrast within aberration‐corrected scanning transmission electron microscope. In contrast to the well‐established octahedral interstitial sites for hydrogen in the bulk, subsurface hydrogen atoms are directly identified to oc.
Nature‐derived cyclic peptides have proven to be a vast source of inspiration for advancing modern pharmaceutical design and synthetic chemistry. The focus of this review is sunflower trypsin inhibitor‐1 (SFTI‐1), one of the smallest disulfide‐bridged cyclic peptides found in nature. SFTI‐1 has an unusual biosynthetic pathway that begins with a dual‐purpose albumin precursor and ends with the production of a high affinity serine protease inhibitor that rivals other inhibitors much larger in size. Investigating the molecular basis for SFTI‐1’s rigid structure and adaptable function has planted seeds for thought that have now blossomed in several different fields. Here we survey these applications to highlight the growing potential of SFTI‐1
Dual‐site catalyst allows for a synergetic reaction in the close proximity to enhance catalysis. It is highly desirable to create dual‐site interfaces in single‐atom system in order to maximize the effect. Herein, we report a cation‐deficient electrostatic anchorage route to fabricate an atomically dispersed platinum‐titania catalyst (Pt 1 O1 /Ti 1‐x O 2 ), which shows greatly enhanced hydrogen evolution activity, surpassing that of the commercial Pt/C catalyst in mass by a factor of 53.2. Operando techniques and density functional theory calculations reveal that Pt 1 O1 /Ti 1‐x O 2 experiences a Pt‐O dual‐site catalytic pathway, where the inherent charge transfer within the dual sites encourages the jointly coupling protons and plays the k.
We report a new visible light‐mediated carbonylative amidation of aryl, heteroaryl and alkyl halides. A tandem catalytic cycle of [Ir(ppy) 2 (dtb‐bpy)] + generates a potent iridium photoreductant via a second catalytic cycle in the presence of DIPEA which productively engages aryl bromides, iodides and even chlorides as well as primary, secondary and tertiary alkyl iodides. The versatility of the in‐situ generated catalyst is illustrated by compatibility with aliphatic and aromatic amines, high functional group tolerance and the late‐stage amidation of complex natural products.
Here an efficient copper‐catalyzed cascade cyclization of azide‐ynamides via α‐imino copper carbene intermediates is reported, which represents the first generation of α‐imino copper carbenes from alkynes. This protocol enables the practical and divergent synthesis of an array of polycyclic N‐heterocycles in generally good to excellent yields with broad substrate scope and excellent diastereoselectivities. Moreover, such an asymmetric azide‐ynamide cyclization has been achieved with high enantioselectivities (up to 98:2 e.r.) by employing BOX‐Cu complexes as chiral catalysts. Thus, this protocol constitutes the first example of asymmetric azide‐alkyne cyclization. The proposed mechanistic rationale for this cascade cyclization is further su.
1,4‐Diazabicyclo[2.2.2]octane (dabco) and its derivatives have been extensively utilized as building units of excellent molecular ferroelectrics for decades. However, the homochiral dabco‐based ferroelectric remains a blank. Herein, by adding a methyl (Me) group accompanied by the introduction of homochirality to the [H2dabco]2+ in the non‐ferroelectric [H2dabco][TFSA]2 (TFSA = bis(trifluoromethylsulfonyl)ammonium), we successfully designed enantiomeric ferroelectrics [R and S‐2‐Me‐H2dabco][TFSA]2. The two enantiomers show two sequential phase transitions with transition temperature (Tc) as high as 405.8 K and 415.8 K, which is outstanding in both dabco‐based ferroelectrics and homochiral ferroelectrics. To our knowledge, [R and S‐2‐Me‐H2da.
Realizing mechanochromism in rigid molecular systems is very important and highly desirable to broaden their potential applications. Here, a novel and practicable strategy to rationally obtain the reversible mechanochromic luminescent (MCL) material with high‐contrast ratio (green versus red) has been established. Namely, by introducing a volatile third party (small‐sized solvent molecules) into the lattice of charge transfer (CT) cocrystal of mixed‐stacking 1:1 coronene (Cor.) and napthalenetetracarboxylic diimide (NDI), a noteworthy reconfigurable molecular assembly is ingeniously achieved due to the loosely packing arrangement as well as weakened intermolecular interactions. Accordingly, the CT excited state, strongly corresponding to th.
DNA nanostructures have shown potentials in cancer therapy. However, current clinical practice is hampered by the difficulty to deliver them into cancer cells and susceptibility to nuclease degradation. To overcome these limitations, we report herein a periodically‐ordered nick‐hidden DNA nanowire (NW) with high serum stability and active targeting functionality. The inner core is made of multiple‐connected DNA double helices and the outer shell is composed of regularly‐arranged standing‐up hairpin aptamers. All terminals of the components are hidden from nuclease attacks while the target‐binding sites are exposed to allow delivery to the cancer target. The DNA NW remains intact over 24‐h incubation in serum solution. Animal imaging and cel.
PB&J? Phosphinoboration across a triple bond catalyzed by tributyl phosphine was achieved. The trans‐α‐phosphino‐β‐boryl acrylate products are obtained in moderate to good yield with high regio‐ and Z‐selectivity. This reaction operates under mild conditions and demonstrates good atom economy, requiring only a modest excess of the phosphinoboronate. Abstract. We report the first trans phosphinoboration of internal alkynes. With an organophosphine catalyst, alkynoate esters and the phosphinoboronate Ph2P‐Bpin are efficiently converted into the corresponding trans‐α‐phosphino‐β‐boryl acrylate products in moderate to good yield with high regio‐ and Z‐selectivity. This reaction operates under mild conditions and demonstrates good atom economy, r.
Hydrogenase enzymes are excellent proton reduction catalysts and therefore provide clear blueprints for the development of nature inspired synthetic analogs. Mimicking their catalytic center is straightforward but mimicking the protein matrix around the active site and all its functions remains challenging. Synthetic models lack this precisely controlled second coordination sphere that provides substrate preorganization and catalyst stability and, as a result, their performances are far from those of the natural enzyme. In this contribution we report a strategy to easily introduce a specific yet customizable second coordination sphere around synthetic hydrogenase models by encapsulation inside M 12 L 24 cages and at the same time create a p.
A facile template‐free method is developed for the synthesis of functional cross‐linked polyphosphazene nanospheres with tunable hollow structures and properties. After coordinating with metal ions, these nanospheres are directly pyrolyzed to afford mesoporous hollow carbon nanospheres with single atom Co‐N2P2 sites for superior electrocatalysis. Abstract. Heteroatom‐doped polymers or carbon nanospheres have attracted broad research interest. However, rational synthesis of these nanospheres with controllable properties is still a great challenge. Herein, we develop a template‐free approach to construct cross‐linked polyphosphazene nanospheres with tunable hollow structures. As comonomers, hexachlorocyclotriphosphazene provides N and P atoms,
The coordination of actinides, lanthanides, as well as strontium and cesium with graphdiyne (GDY) was studied by experiments and theoretical calculations. On the basis of experimental results and/or theoretical calculations, it was suggested that Th 4+ , Pu 4+ , Am 3+ , Cm 3+ and Cs + exist in single ion states on the special triangle structure of GDY with various coordination patterns, in which GDY itself is deformed in different manners. Both experiments and theoretical calculations strongly support that UO 2 2+ , La 3+ , Eu 3+ , Tm 3+ and Sr 2+ are not adsorbed by GDY at all. The distinguished adsorption behaviors of GDY afford an important strategy for highly selective separation between actinides and lanthanides, Th 4+ and UO 2 2+ , Cs.
Center of attention: Multifunctional platinum/lithium cobalt oxide (Pt/LiCoO2) heterostructures are prepared that allow the active center to be switched between Pt species for the hydrogen evolution reaction (HER) and LiCoO2 species for the oxygen evolution reaction (OER). Abstract. Designing cost‐effective and efficient electrocatalysts plays a pivotal role in advancing the development of electrochemical water splitting for hydrogen generation.
A precise thermal sensing DNA nanojoint comprised of two interlocked DNA rings switches reversibly between a static and mobile state at different temperatures. The temperature response range is tuned by changing the length or sequence of the hybridizing region between two rings, which, unlike non‐interlocked systems, is independent from its concentration. Abstract. The ability to precisely measure and monitor temperature at high resolution at the nanoscale is an important task for better understanding the thermodynamic properties of functional entities at the nanoscale in complex systems, or at the level of a single cell. However, the development of high‐resolution and robust thermal nanosensors is challenging. The design, assembly, and char.
A catalytic enantioselective access to disubstituted functionalized gem ‐difluorocyclopropanes, which lie among emerging fluorinated motifs, was developed by asymmetric transfer hydrogenation of gem ‐difluorocyclopropenyl esters, catalyzed by Noyori‐Ikariya ( p ‐cymene)‐ruthenium(II) complex, with ( N ‐tosyl‐1,2‐diphenylethylenediamine) as chiral ligand and isopropanol as hydrogen donor.
Divergent enantioselective total syntheses of five naturally occurring post‐iboga indole alkaloids, dippinine B ( 3 ) and C ( 4 ), 10,11‐demethoxychippiine ( 8 ), 3‐ O ‐methyl‐10,11‐demethoxychippiine ( 9 ), and 3‐hydroxy‐3,4‐secocoronaridine ( 11 ), and two analogues 11‐demethoxydippinine A ( 2 ) and D ( 6 ), were presented for the first time.
Carbonyls reconciled: Electrostatics and orbital interactions have both been implicated in governing carbonyl interactions. A combined experimental and computational approach reconciles these conflicting explanations of the physiochemical origin of the interaction, demonstrating that orbital delocalisation augments electrostatic control, but for very close carbonyl contacts. Abstract. Interactions between carbonyl groups are prevalent in protein structures. Earlier investigations identified dominant electrostatic dipolar interactions, while others implicated lone pair n→π* orbital delocalisation. Here these observations are reconciled. A combined experimental and computational approach confirmed the dominance of electrostatic interactions in.

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