ACS Organic & Inorganic Au最新文献

A series of vanadium(III), vanadyl(IV/V) species, inorganic metal oxides, and transition-metal oxides was examined as cocatalysts with Cu(0) powder for copper(I)-catalyzed azide-alkyne cycloaddition. Among them, vanadyl(IV) species bearing acetylacetonate, acetate, and sulfate, vanadyl(V) isopropoxide, and vanadate were suitable for the click reactions of per-acetyl and per-benzyl β-azido glycosides with three different terminal alkynes in CH₃CN. Water-soluble vanadyl(IV) sulfate was further selected for efficient click reactions for unprotected β-glycosyl azides and even compatible with a thiol-containing substrate in aqueous media at ambient temperature.

Quadrupolar A-D-A-type 1,4-dihydropyrrolo[3,2-b]pyrroles (DHPPs) bearing pyridinium and quinolinium substituents emit in the 500–600 nm region. The enhancement of electronic communication between the electron-rich heterocyclic core and electron-deficient peripheral substituents turned out to be crucial for achieving emission enhancement in viscous media. DHPP bearing two 4-pyridinium substituents has optical brightness 34,000 in glycerol and only 700 in MeOH, as evidenced by measurements of the emission intensity and fluorescence lifetimes in a series of polar solvents. Such behavior makes it an excellent candidate for viscosity probes in fluorescence microscopy, as demonstrated by the fluorescence imaging of H9C2 cardiomyocytes.

In the present manuscript, we have developed a unique catalytic system by merging photoexcited ketone catalysis, halogen atom transfer (XAT), and nickel catalysis to forge C(sp³)–C(sp²) cross-electrophile coupling products from unactivated iodoalkanes and (hetero)aryl bromides. The synergistic catalytic system works under mild reaction conditions and tolerates a variety of functional groups; moreover, this strategy allows the late-stage modification of medicinally relevant molecules. Preliminary mechanistic studies reveal the role of the α-aminoalkyl radical, which further participates in the XAT process with alkyl iodides to generate the desired alkyl radical, which eventually intercepts with the nickel catalytic cycle to liberate the products in good to excellent yields.

Dual nickel-photoredox-enabled direct synthesis of amides through cross-coupling of cesium oxamates with aryl bromides has been developed. This methodology’s key advantages are mild reaction conditions, utilizing organic dye as a photocatalyst, employing readily available starting chemicals as coupling partners, and late-stage carbamoylation of pharmaceutically relevant molecules. DFT studies suggested that the nickel catalytic cycle proceeds via a radical addition pathway prior to the oxidative insertion.

Electrosynthesis is a popular, environmentally friendly substitute for conventional organic methods. It involves using charge transfer to stimulate chemical reactions through the application of a potential or current between two electrodes. In addition to electrode materials and the type of reactor employed, the strategies for controlling potential and current have an impact on the yields, product distribution, and reaction mechanism. In this Review, recent advances related to electroanalysis applied in electrosynthesis were discussed. The first part of this study acts as a guide that emphasizes the foundations of electrosynthesis. These essentials include instrumentation, electrode selection, cell design, and electrosynthesis methodologies. Then, advances in electroanalytical techniques applied in organic, enzymatic, and microbial electrosynthesis are illustrated with specific cases studied in recent literature. To conclude, a discussion of future possibilities that intend to advance the academic and industrial areas is presented.

Spinel oxides with the general formula AB₂O₄ comprise a large family of compounds covering a very wide range of band-gap values (1 eV < E_g < 8 eV) as a function of the nature of the metallic cations A and B. Owing to this, the physical properties of these materials have been largely exploited both from a fundamental point of view, for their variable electronic properties, and for their possible use in numerous engineering applications. Herein, the modeling of ZnAl₂O₄, ZnGa₂O₄, MgAl₂O₄, and MgGa₂O₄ cubic spinel oxides has been carried out by using the semiempirical approach based on the difference of electronegativity between oxygen and the average electronegativity of cations present in the oxides. The results of recent theoretical extensions of our semiempirical approach to ternary and quaternary oxides have been tested for spinel oxides with metallic ions occupying both octahedrally and tetrahedrally coordinated sites in different ratios. A detailed analysis of the experimental band-gap values and comparison with the theoretically estimated values has been carried out for ternary ZnAl₂O₄, ZnGa₂O₄, MgAl₂O₄, and MgGa₂O₄ spinels as well as for double spinels Mg(Al_2xGa_2–x)O₄ and Zn(Al_2xGa_2–x)O₄, and quaternary mixed oxides (Zn_xMg_(1–x))Al₂O₄ and (Zn_xMg_(1–x))Ga₂O₄. The wide range of band-gap values reported in the literature for simple or double spinels has been related to the different preparation methods affecting the grain dimension of crystalline spinel samples as well as to the presence of crystallographic defects and/or impurities in the spinel matrix. The good agreement between experimental band-gap values and the theoretical ones strongly supports the use of our semiempirical approach in the area of band-gap engineering of new materials.

The ever-increasing landscape of heterogeneous catalysis, pure and applied, utilizes many different catalysts. Academic insights along with many industrial adaptations paved the way for the growth. In designing a catalyst, it is desirable to have a priori knowledge of what structure needs to be targeted to help in achieving the goal. When focusing on catalysis, one needs to cope with a vast corpus of knowledge and information. The overwhelming desire to exploit catalysis toward commercial ends is irresistible. In today’s world, one of the requirements of developing a new catalyst is to address the environmental concerns. The well-established heterogeneous catalysts have microporous structures (<25 Å), which find use in many industrial processes. The metal–organic framework (MOF) compounds, being pursued vigorously during the last two decades, have similar microporosity with well-defined pores and channels. The MOFs possess large surface area and assemble to delicate structural and compositional variations either during the preparation or through postsynthetic modifications (PSMs). The MOFs, in fact, offer excellent scope as simple Lewis acidic, Brönsted acidic, Lewis basic, and more importantly bifunctional (acidic as well as basic) agents for carrying out catalysis. The many advances that happened over the years in biology helped in the design of many good biocatalysts. The tools and techniques (advanced preparative approaches coupled with computational insights), on the other hand, have helped in generating interesting and good inorganic catalysts. In this review, the recent advances in bifunctional catalysis employing MOFs are presented. In doing so, we have concentrated on the developments that happened during the past decade or so.

An arylation strategy allowing the conversion of alkyl 2-((diphenoxyphosphoryl)oxy)-2-arylacetates to α,α-diaryl esters is reported. This transformation can be promoted by TfOH when the starting organic phosphates do not carry para-alkoxy groups on their aryl rings, but it does not require any additives when such groups are present. These alkyl 2-((diphenoxyphosphoryl)oxy)-2-arylacetates can be readily accessed from the insertion of diphenyl phosphate into aryldiazoacetates.

Topochemistry refers to a generic category of solid-state reactions in which precursors and products display strong filiation in their crystal structures. Various low-dimensional materials are subject to this stepwise structure transformation by accommodating guest atoms or molecules in between their 2D slabs or 1D chains loosely bound by van der Waals (vdW) interactions. Those processes are driven by redox reactions between guests and the host framework, where transition metal cations have been widely exploited as the redox center. Topochemistry coupled with this cationic redox not only enables technological applications such as Li-ion secondary batteries but also serves as a powerful tool for structural or electronic fine-tuning of layered transition metal compounds. Over recent years, we have been pursuing materials design beyond this cationic redox topochemistry that was mostly limited to 2D or 1D vdW systems. For this, we proposed new topochemical reactions of non-vdW compounds built of 2D arrays of anionic chalcogen dimers alternating with redox-inert host cationic layers. These chalcogen dimers were found to undergo redox reaction with external metal elements, triggering either (1) insertion of these metals to construct 2D metal chalcogenides or (2) deintercalation of the constituent chalcogen anions. As a whole, this topochemistry works like a “zipper”, where reductive cleavage of anionic chalcogen–chalcogen bonds opens up spaces in non-vdW materials, allowing the formation of novel layered structures. This Perspective briefly summarizes seminal examples of unique structure transformations achieved by anionic redox topochemistry as well as challenges on their syntheses and characterizations.