Deoxyfluorinationof Hydroxy-Substituted Boronates

Cyanoacetylenic alcohols, R1R2C(OH)C≡C–CN, the closest derivatives of cyanoacetylene, an abundant interstellar molecule, are now becoming important compounds in the area of modern organic synthesis that tends to mimic Nature. The presence of highly reactive C≡C and C≡N bonds in close proximity to a hydroxy group endows cyanoacetylenic alcohols with a chemical trinity of mutually influencing functions, leading to a myriad number of chemical transformations. All reactions of cyanoacetylenic alcohols parallel modern organic synthesis, whilst being biomimetic. To react, they do not need transition metals (and in most cases, no metals at all, except for physiologically indispensable Na+ and K+), proceed at ambient temperature and often in aqueous media. Fundamentally, their reactions are 100% atom-economic because they are almost exclusively addition processes. Typically, the cyano, acetylene and hydroxy functions of cyanoacetylenic alcohols behave as an inseparable entity, leading to reaction products with multiple functional groups. This allows hydroxy, carbonyl, carboxylic, imino, amino, amido, cyanoamido, cyano, various P-containing, ether and ester functions, along with double bonds, different fundamental heterocycles (furans, furanones, pyrazoles, oxazoles, pyridines, pyrimidines, purines, etc.) and diverse polycyclic systems to be integrated in a single molecular architecture. This review focuses on an analysis and generalization of the knowledge that has accumulated on the chemistry of cyanoacetylenic alcohols, mostly over the past 15 years.1 Introduction2 Nucleophilic Addition to Cyanoacetylenic Alcohols and Subsequent Transformations of the Adducts3 Annulation with Nonaromatic Nitrogen Heterocycles4 Annulation with Aromatic Nitrogen Heterocycles5 Modification of Amino Acids6 Modifications of Nucleobases7 Modification of Nucleosides8 Conclusion

An efficient and mild methodology for the oxidation of primary and secondary alcohols to the corresponding carbonyl functions is described with N,N,N′,N′‐tetrabromobenzene‐1,3‐disulfonamide and poly(N‐bromobenzene‐1,3‐disulfonamide) using microwave irradiation under solvent‐free conditions. Aliphatic, benzylic and allylic alcohols are rapidly oxidized without over‐oxidation to carboxylic acids. Secondary carbinols are slowly oxidized so that the reaction is highly chemoselective.

Flavonoids and hydrolyzable tannins isolated from Pelargonium reniforme were evaluated for their antioxidant ability using a 1,1-diphenyl-2-picrylhydrazyl (DPPH) radical generating system and a luminol-dependent chemiluminescence assay. In both assays, the polyphenols tested showed higher radical scavenging activities than the reference antioxidant, ascorbic acid (IC50 2.6-32.9 microM vs 40.9 microM in the DPPH test, and 2-25 times stronger effects in the chemiluminescence assay). A comparison of the flavonoids and the tannins showed that the latter have more potential than the former. Structural requirements for marked antioxidant activities of hydrolyzable tannins were the presence of galloyl and hexahydroxydiphenoyl groups, and apparently carbonyl (ester) functionalities in oxidatively modified dehydrohexa-hydroxydiphenoyl moieties. For flavonoids, it appeared that a catechol (3',4'-dihydroxy) element in the B-ring were important determinants and that O-glycosides were more effective than flavone-based C-glucosyls. Conspicuously, introduction of a galloyl group significantly enhanced their potentials. The demonstrated marked antioxidant effects of the polyphenols provide a clue for beneficial effects of P. reniforme in the treatment of liver disorders among several ethnic groups in areas of southern Africa.

Synthesis of functionalized phenyl, 2-thienyl, and N-methyl-pyrrol-2-yl Fischer carbene complexes of chromium and tungsten was achieved via a Negishi cross-coupling reaction of metalated aminocarbenes in the presence of a palladium catalyst. The reverse approach, i.e., coupling bromocarbenes with organozinc reagents, is also feasible and is particularly useful with alkoxycarbene complexes, metalation of which is not possible. Both these procedures are also suitable for the cross-coupling of molybdenum amino- and alkoxycarbene complexes. The presented methodology enables an access to the new amino and alkoxy carbene complexes bearing aldehyde, ketone, nitrile, and ester functionality.

An efficient and one-pot procedure for the synthesis of arylated and stereodefined allylic alcohols has been achieved through zirconium-mediated multicomponent coupling reactions of alkynes, aldehydes (or ketones), and aryl iodides. The subsequent intramolecular Friedel-Crafts reactions of these allylic alcohols catalyzed by Brønsted or Lewis acids afford highly substituted indenes and spiroindenes under extremely mild reaction conditions. This methodology also provided a highly efficient route to the synthesis of spiroindenepiperidines.

Benzyl ether protected polyhydroxylated alkene compounds containing allylic alcohol, ether or ester functionality undergo a stereospecific cyclisation reaction upon treatment with TFA-acetonitrile-toluene with inversion of configuration at the allylic position and loss of a benzyl ether to give tetrahydrofurans.

Starting from L‐ or D‐threonine (I) or (VIII) the stereoisomeric (E)‐β,γ‐enolates (IV)‐(VII) are prepared, as shown for (IV) and (VI), by organocopper reaction of the corresponding γ‐mesyloxy‐α,β‐enoates such as (II) or (IX).

In 1980, two groups reported the synthesis of unsubstituted polythiophene utilizing 2,5-dibromothiophene via a Ni-catalyzed method. Since then, several different types of catalysts were employed for the polymerization of 2,5dibromothiophene. Unfortunately, low molecular weight polymers generally resulted from these attempts. Even though these methods provided interesting materials, there was a big barrier to utilize this polymer due to the lack of processability. In order to overcome this difficulty, an alkyl chain was introduced on 3-position of the thiophene ring. Of the many methods, metal-catalyzed cross-coupling polymerization was most frequently used, and the synthesized polythiophenes containing an alkyl group equal or greater than C4 are soluble in common organic solvents. This wellestablished method, however, has significant drawbacks generating inconsistent results and regiorandom polymers. As is known, the regioregularity of the 3-substituted polythiophene plays a critical role in electronic and optical devices. Consequently, developing the efficient methods of preparing highly regioregular head-to-tail poly-3-alkylthiophenes is of high value. This goal was achieved by two research groups, seperately. Rieke and coworkers reported a synthetic approach to the preparation of regioregular poly-3alkylthiophene utilizing thienylzinc bromide. The other synthetic method, the McCullough method, was performed by using the Kumada cross-coupling method. Even though extensive studies have focused on the preparation and application of the linear alkyl-substituted polythiophenes, there is an increasing need to develop various types of polythiophenes because these polymers have a wide range of potential possibilities of being used in material chemistry. Recent reports also showed that the chemical composition of the P3HT significantly affect the device performance. Therefore, many efforts were devoted to finding new strategies for the preparation of functionalized P3HTs. One of the first attempts was to introduce a heteroatom on the thiophene ring. This has been accomplished wherein the thiophene has an oxygen atom directly attached to the ring. Furthermore, polythiophenes containing other functionalities such as an alcohol, ester, and urethane were prepared. In addition, thiophenes bearing a carboxylate or sulfonate functionality were introduced for the synthesis of water-soluble polythiophenes. More importantly, a recent report showed that P3HT-phosphonic ester was employed to improve the power conversion efficiencies in hybrid solar cells. We have developed a versatile synthetic method for polythiophenes bearing a phosphonic ester functionality on the 3-position. In addition, we wish to report more results obtained from the study on the preparation of polythiophenes bearing several different functional groups. In 2003, McCullough et al. reported the synthesis of poly[3-(6-diethylphosphorylhexyl)thiophene] utilizing the Stille method. This synthesis required a difficult monobromination as well as cryogenic condition (−70 C) for the preparation of the reactive organometallic intermediate. This study also pointed out that the GRIM and Kumada methods are not reliable for the preparation of polythiophenes containing the phosphonic ester moiety. Although poly[3(11-diethylphosphorylundecyl)thiophene] was also synthesized by Kowalik and Tolbert using an organozinc route, we have focused on a more practical synthetic method. It was accomplished starting with readily available 2,5-dibromo-3-(6-bromohexyl)thiophene (4), which is easily prepared by known literature methods. The use of this route provided a huge advantage over the previously reported studies requiring a regioselective monobromination of thiophene ring. As shown in Scheme 1, in our study, the phosphonate ester group was easily provided by the MichaelisArbuzov reaction with 4 which was readily obtained by the simple bromination of 3 with NBS. The oxidative addition of active zinc to 5 was completed in 20 min at 0 C showing 75:25 ratio regioselectivity. The resulting mixture of thienylzincs (6 and 7, Scheme 1) were polymerized in the presence of 0.3 mol % of Ni(dppe)Cl2 at room temperature yielding the title polymer (P1) in 93%. The UV-vis analysis exhibited a λmax of 440 nm in chloroform solution. This is compatible with the literature value (λmax 442 nm). 11a

First described by the groups of Sharpless (Rostovtsev et al., Angew. Chem., Int. Ed., 2002, 41, 2596) and Meldal (Tornoe et al., J. Org. Chem., 2002, 67, 3057) in 2002, Cu(I)-catalyzed azide–alkyne cycloaddition (CuAAC) became one of the most effective and reliable synthetic tools in diverse areas of modern chemistry, such as organic, medicinal and polymer chemistry, material science and chemical biology. The advantages of this reaction are high selectivity, simple reaction conditions, wide scope and excellent functional group tolerance. This efficient transformation can be used for the synthesis of various 1,2,3-triazoles. On the other hand, CuAAC can be efficiently used for bioconjugation of two units bearing alkyne and azide functions via the triazole moiety. Moreover, the use of azides and alkynes bearing orthogonal functional groups in this reaction opens broad opportunities for the synthesis of valuable polyfunctionalized triazole-containg molecules. Thus, the initial discussion is focused on synthetic applications of functionally substituted azides and terminal alkynes in the CuAAC, combined with other transformations. The prominent part of this review is devoted to an application of these bi (or tri)-functional reagents for the design, synthesis or labeling of biologically active molecules.

The processability of giant (macro)molecules into ultrapure and highly ordered structures at surfaces is of fundamental importance for studying chemical, physical and biological phenomena, as well as their exploitation as active units in the fabrication of hybrid devices. The possibility of handling larger and larger molecules provides access to increasingly complex functions. Unfortunately, larger molecules commonly imply lower processability due to either their low solubility in liquid media or the occurrence of thermal cracking during vacuum sublimation. The search for novel strategies to process and characterize giant building blocks is therefore a crucial goal in materials science. Here we describe a new general route to process, at surfaces, extraordinarily large molecules, that is, synthetic nanographenes, into ultrapure crystalline architectures. Our method relies on the soft-landing of ions generated by solvent-free matrix-assisted laser desorption/ionization (MALDI). The nanographenes are transferred to the gas phase, purified and adsorbed at surfaces. Scanning tunnelling microscopy reveals the formation of ordered nanoscale semiconducting supramolecular architectures. The unique flexibility of this approach allows the growth of ultrapure crystalline films of various systems, including organic, inorganic and biological molecules, and therefore it can be of interest for technological applications in the fields of electronics, (bio)catalysis and nanomedicine.

The synthesis of silacycles is highly appealing due to their important applications in organic synthesis, medicinal chemistry, and materials chemistry. However, sila-tetralins and sila-benzosuberanes are surprisingly under-represented due to a lack of general methods to access these compounds. We successfully developed a Pd-catalyzed strain-release silicon-based cross-coupling as an unprecedented ring-expansion method, which constitutes a general route for preparing diverse sila-tetralins and sila-benzosuberanes.

Purpose: This paper aims to enhance the design of Solid-State Transformers (SSTs) operating at medium and high frequencies (MF/HF) by optimizing key performance attributes such as efficiency, power density, and thermal management through the use of advanced nanocrystalline materials. Design/Methodology/Approach: An interactive MATLAB-based magnetic characterization tool was utilized to evaluate transformer core losses and efficiencies with various core materials. A hybrid optimization methodology integrating L9 Taguchi design and Response Surface Methodology (RSM) was employed to design a 2 kVA, 20 kHz, 600/60 V shell-type SST. Design parameters such as duty cycle, window utilization factor, insulation material, and core series were optimized across three levels to achieve minimal losses and maximum efficiency. Research Limitations/ Implications: While the study demonstrates promising results, the research is limited to a specific transformer rating and operating frequency, indicating a need for further exploration across varying ratings and frequencies. Practical Implications: The findings contribute to the development of efficient and compact SSTs, benefiting renewable energy systems, electric vehicle charging, grid-connected converters, and compact power supplies by ensuring reduced thermal stress and enhanced durability. Originality/Value: This research highlights the efficacy of integrating advanced nanocrystalline materials and hybrid optimization methodologies in SST design, offering substantial improvements in energy efficiency and operational reliability, thus contributing valuable insights to transformer design and application fields. Major Findings: The optimized Solid-State Transformer (SST) design achieved an impressive efficiency of 99.5832% with core and winding losses of 6.2391 W and 2.2457 W, respectively. The temperature rise was minimized to 11.4541°C, confirming the effectiveness of the hybrid optimization approach. Validation through fuzzy inference systems demonstrated robust alignment with both theoretical and experimental results.

New β-amino thiols as efficient catalysts for highly enantioselective alkenylzinc addition to aldehydes

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Quinolines are key heterocyclic motifs with broad utility in pharmaceuticals, agrochemicals, and materials science. The development of efficient and sustainable synthetic routes to access structurally diverse quinolines remains an important goal in organic chemistry. This review focuses on the recent advances in palladium-catalyzed strategies for quinoline synthesis, emphasizing oxidative and tandem annulation methods. Reactions are categorized by substitution patterns on the quinoline scaffold—namely 2-aryl, 4-substituted, 2,3-, 2,4- and 3,4-disubstituted, 2,3,4-trisubstituted, and annulated derivatives—to facilitate mechanistic comparisons and highlight structural scope. Together, the reviewed strategies showcase the range of mechanistic possibilities available for constructing quinoline scaffolds via palladium catalysis. Overall, these Pd-catalyzed approaches offer powerful and versatile tools for the synthesis of complex quinoline frameworks, providing valuable alternatives to classical heterocycle forming reactions.