Enantioselective Aromatic Amination?

The atroposelective formation of C−N bonds has recently emerged within the field of amination reactions. On first sight, it may seem quite surprising that such an ancient class of organic coupling reactions (Gabriel, Ullmann, Goldberg, Buchwald, Hartwig and many others) has so few enantioselective solutions, and this in spite of asymmetric synthesis being now a mature concept and field. Why should enantioselective C−N bond formation be so difficult? This question and some of the first examples that promise an imminent change of paradigm are herein discussed.     

The extended Hulburt–Hirschfelder‐long‐range oscillator model for direct‐potential‐fit analysis

In the present work, an extended Hulburt–Hirschfelder oscillator model is proposed as a means of simplifying potential energy functions for direct‐potential‐fit analyses. The new potential energy function is joined smoothly to the long‐range inverse‐power dispersion energy expression. The new model is employed in direct‐potential‐fits using spectroscopic line positions that involve the ground electronic states of the principal isotopologues of hydrogen iodide and carbon monoxide, and the ground and first singlet‐sigma excited states of hydrogen fluoride and hydrogen chloride. The present methodology is found to lead to compact, flexible, and robust representations for the potential energy that compare favorably with the results of past work where more complicated models were employed.     

Electrochemical Detection of Hemoglobin: A Review

Hemoglobin (Hb) is a tetrameric hemoprotein that is located in red blood cells (RBCs) and is responsible for O₂ transport in the circulatory system. Conventionally, Hb assay is a specific and sensitive indicator for the diagnosis of anemia and other related diseases. To date, various methods have been used for the analysis of Hb, and of these, electrochemical method is the simplest and reliable technique. Therefore, several approaches have been reported for the quantification of Hb, including the direct electron transfer (DET) with or without a mediator onto the electrode surface, molecular imprinted polymer (MIPs), and immunoreaction. To realize the direct electrochemistry of Hb, the modification of the electrode surface either with a mediator or catalyst to promote the redox process, which can be applied for the sensitive and selective detection of Hb. This review contains a comprehensive introduction to electrochemical Hb detection methods using modified electrode surfaces. Finally, the review gives a brief insight into the electrochemical sensing platform developed for the analysis of other type of globins such as, myoglobin and glycated hemoglobin. The objectives of this review are to summarize various electrochemical detection methods for Hb and to facilitate future development of new sensing platforms for the medical and healthcare applications.     

Organocatalytic Enantioselective Synthesis of Chiral Diarylmethylamines from Racemic Alcohols

An organocatalytic approach for direct conversion of racemic diarylmethanols to valuable chiral diarylmethylamines is described. Different from the previously reported elegant “borrowing hydrogen” approach, the present process employs a distinct complementary formal S_N1 strategy. This approach enjoys excellent enantioselectivity, mild conditions, broad scope, and easy product derivatization. Mechanistically, control experiments also provided important insights into some notable features, such as substrate kinetic resolution and reversibility as well as the critical role of the ortho‐ hydroxy group in the substrate.     

Synthesis of Diverse Functionalized Quinoxalines by Oxidative Tandem Dual C−H Amination of Tetrahydroquinoxalines with Amines

The tandem dual C−H amination of tetrahydroquinoxalines with free amines under aerobic copper catalysis conditions has been demonstrated. The synthetic protocol proceeds with good substrate and functional group compatibility, mild reaction conditions, short reaction time, the use of the naturally abundant [Cu]/O₂ catalyst system, excellent chemoselectivity and synthetic efficiency, and with no need for the pre-installation of specific aminating agents, which offers a practical platform for the rapid and diverse synthesis of diaminoquinoxalines. Moreover, this work has shown the potential of single-electron-oxidation-induced C−H functionalization of N-heterocycles, and its application in the development of optoelectronic materials.     

Advanced Polymer Designs for Direct-Ink-Write 3D Printing

The rapid development of additive manufacturing techniques, also known as three-dimensional (3D) printing, is driving innovations in polymer chemistry, materials science, and engineering. Among current 3D printing techniques, direct ink writing (DIW) employs viscoelastic materials as inks, which are capable of constructing sophisticated 3D architectures at ambient conditions. In this perspective, polymer designs that meet the rheological requirements for direct ink writing are outlined and successful examples are summarized, which include the development of polymer micelles, co-assembled hydrogels, supramolecularly cross-linked systems, polymer liquids with microcrystalline domains, and hydrogels with dynamic covalent cross-links. Furthermore, advanced polymer designs that reinforce the mechanical properties of these 3D printing materials, as well as the integration of functional moieties to these materials are discussed to inspire new polymer designs for direct ink writing and broadly 3D printing.     

Two-Step Structure Phase Transition,Dielectric Anomalies,and Thermochromic Luminescence Behavior in a Direct Band Gap 2D Corrugated Layer Lead Chloride Hybrid of [(CH3)4N]4Pb3Cl10

A direct band gap 2D corrugated layer lead chloride hybrid, [(CH₃)₄N]₄Pb₃Cl₁₀ ( 1 ), shows analogous topology to the {Mg₃F₁₀⁴⁻}_∞ layer in Cs₄Mg₃F₁₀, and with the (CH₃)₄N⁺ cations locating in the inorganic layer voids and between the interlayers. Two reversible structural phase transitions occur in 1 at 225/210 K and 328/325 K upon heating/cooling, respectively. On going from the low- to intermediate-temperature phase, the space group changes from P2₁/c to Cmca, and the crystallographic axis perpendicular to the layers is doubled with the order–disorder transformation of (CH₃)₄N ⁺ cations between the interlayers. The intermediate- and high-temperature phases are isomorphic with similar cell parameters and packing structure; their main difference concerns the disorder degree of the (CH₃)₄N ⁺ cations between the interlayers. The two-step structural phase transitions lead to dielectric anomalies around the corresponding T_c. Interestingly, 1 shows multiband emission, originating from the recombination of exciton and emission of defects. Moreover, 1 exhibits divergent thermochromic luminescent features around the T_c on the intermediate to low temperature transition.