Stereoselective Access to Trifunctionalized Z-Allylic Alcohols via Radical-Mediated 1,4-Aryl Migration.

The enantioselective ring-opening reactions of methylenecyclopropanes (MCPs) involving C-C bond activation via oxidative addition of transition metals have been rarely reported. Here, we disclose a Pd/Cu-catalyzed enantio- and regioselective coupling between cyclic imino esters and MCPs to produce α-allylated 2H-pyrrole derivatives. In this reaction, azomethine ylide formed by a chiral copper catalyst with ketimine ester would serve as a nucleophile to react with activated MCPs via palladium catalysis. This bimetallic catalyst system exhibited a broad substrate scope and high regio- and enantioselectivities.

Summary of main observation and conclusionThe radical‐initiated carboxylative cyclization of allylamines with CO2 represents an efficient and highly promising strategy to afford valuable 2‐oxazolidinones. However, the radical precursors and pathways to generate radicals in such processes are still limited. Herein, we report the first Cu‐catalyzed selective oxy‐cyanoalkylation of allylamines with cycloketone oxime esters and CO2 via C—C bond cleavage. Many cyanoalkyl‐substituted 2‐oxazolidinones are obtained in moderate to good yields with high regio‐ and chemo‐selectivities. The utility of this redox‐neutral and cyanide‐free method is demonstrated with mild conditions, broad substrate scope, good functional group tolerance and easy scalability.

Selective C-C Bond Scission of Ketones via Visible-Light-Mediated Cerium Catalysis

The site-specific construction of C(sp3)-C(sp3) bonds via direct reductive cross-coupling between N-heteroarenes and arenes remains an elusive challenge; yet, this underexplored research direction holds significant importance for various fields. Herein, by employing an undivided cell tolerant of air and moisture, we present, for the first time, an electrochemical strategy that enables regioselective C(sp3)-C(sp3) bond formation through the reductive cross-coupling of N-heteroarenes with aryl carboxylic derivatives at room temperature. This transition-metal-free and H2-free method exhibits broad substrate scope, operational simplicity, and high regio- and chemoselectivity. It offers an efficient platform for diversely accessing α-cycloalkylated cyclic amines─valuable scaffolds with widespread applications across various fields. Mechanistic studies indicate a radical-radical cross-coupling pathway between the α-carbon of N-heteroarenes and the para-position of the carbonyl group in carboxylates. This strategy, merging electroreductive dearomatization with in situ radical transformations, will open new avenues for the development of tandem reactions using abundant, yet less reactive (hetero)arene resources.

We report a palladium-catalyzed Hiyama-type defluorinative cross-coupling of allylic gem-difluorides with trimethylsilyl cyanide and silylalkynes via selective C-F bond activation. The reaction involves oxidative addition, Si-F-assisted transmetalation, and reductive elimination, enabling efficient construction of C(sp3)-CN and C(sp3)-C(sp) bonds under mild, additive-free conditions. It features broad substrate scope, excellent functional group tolerance, and high regio- and Z-selectivity, affording diverse monofluorinated alkenes in good to excellent yields. The resulting fluoroalkenes serve as versatile intermediates for downstream functionalization, highlighting the synthetic utility of this Si-F-driven platform.

The book is intended as a problem text for students in inorganic chemistry at the senior undergraduate and beginning graduate level. It is a compilation of 300 problems that had been designed by the authors for teaching inorganic chemistry courses, either as take-home assignments or examination questions. Notwithstanding the focus on structural aspects of inorganic chemistry indicated in the title the scope is much broader. The topics covered comprise Atomic and Molecular Electronic States, Atomic Orbitals, Hybrid Orbitals, Molecular Symmetry, Molecular Geometry and Bonding, Crystal Field Theory, Molecular Orbital Theory, Vibrational Spectroscopy, and Crystal Structure. Yet the central theme running through these topics is symmetry, molecular or crystalline. Helpful appendices, a bibliography with 150 citations, and a subject index complete the text. The origins of the book go back to the early 80s when the first version of this compilation, entitled Problems in Inorganic and Structural Chemistry, was published by T. C. W. Mak, K. Y. Hui, O. W. Lan and W.-K. Li. During decades of practical use it has been revised and updated. The renowned senior authors Thomas Chung Wai Mak and Wai-Kee Li are now Emeritus Professors of Chemistry. In this sequel book their great expertise in inorganic and physical chemistry is complemented by Yu-San Cheung and Kendrew Kin Wah Mak who are teaching physical and organic chemistry at the Chinese University of Hong Kong. Indeed, the optimization by generations of students and the extension to further aspects of chemistry resulted in a wide range of clearly formulated, challenging problems along with their solutions and helpful explanations. This mature workbook allows students to profoundly test their knowledge in several essential fields of chemistry. The outstanding quality of the content, the high quality printing and the affordable paperback edition make Problems in Structural Inorganic Chemistry highly attractive for students and instructors especially in inorganic and physical chemistry.

Classical Julia–Kocienski fluoroolefination represents an indispensable platform for the construction of monofluoroalkenes. Nevertheless, its complex multistep mechanistic manifold along with the u...

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Background: The Hetero-Diels-Alder reaction (HDAR) is a method extensively used in organic chemistry as a tool in the synthesis of innumerous polycyclic compounds in particular nitrogen compounds, presents in many natural products, medicinally relevant substances and organic materials. The literature describes innumerable studies of HDAR using classic methods and modern developments such as reactions on the solid phase, the use of catalysts, transformations in aqueous solution and under microwaves. Objective: This review describes a variety of HDAR focused on obtaining nitrogen-containing compounds of considerable chemical and biological interest, and highlighting reported biological activity. Conclusion: This review has shown the importance of the HDA reaction as a tool of organic chemistry in the synthesis of nitrogen compounds. This type of reaction presents important properties including bond-forming economy, high regio- and stereoselectivities and thus provides highly efficient routes to access a wide range of polycyclic compounds. In addition to the variety of nitrogen compounds synthetized successfully by this method, they present relevant biological properties.

Continuous flow systems for chemical synthesis are becoming a major focus in organic chemistry and there is a growing interest in the integration of biocatalysts due to their high regio‐ and stereoselectivity. Methods established for 3D bioprinting enable the fast and simple production of agarose‐based modules for biocatalytic reactors if thermally stable enzymes are available. We report here on the characterization of four different cofactor‐free phenacrylate decarboxylase enzymes suitable for the production of 4‐vinylphenol and test their applicability for the encapsulation and direct 3D printing of disk‐shaped agarose‐based modules that can be used for compartmentalized flow microreactors. Using the most active and stable phenacrylate decarboxylase from Enterobacter spec. in a setup with four parallel reactors and a subsequent palladium(II) acetate‐catalysed Heck reaction, 4‐hydroxystilbene was synthesized from p‐coumaric acid with a total yield of 14.7 % on a milligram scale. We believe that, due to the convenient direct immobilization of any thermostable enzyme and straightforward tuning of the reaction sequence by stacking of modules with different catalytic activities, this simple process will facilitate the establishment and use of cascade reactions and will therefore be of great advantage for many research approaches.

Carbohydrates are synthetically challenging molecules with essential biological functions in all living systems. The selective synthesis and modification of carbohydrates are crucial for investigating their biological functions. Controlling chemo-, regio-, and stereoselectivity is a central theme in carbohydrate synthesis. Achieving the full set of stereoisomers of carbohydrate derivatives would significantly enhance the efficiency of building compound libraries for biological studies and drug discovery. However, the selective functionalization of seemingly identical hydroxyl groups in carbohydrates remains a long-standing challenge in organic chemistry. In carbohydrate synthesis, achieving precise control of both relative configurations in catalyst-controlled reactions that create a new stereocenter presents a significant synthetic challenge. Herein, we developed an efficient method for the stereodivergent O-alkylation of carbohydrate hydroxyl groups via Rh(II)/chiral phosphoric acid-cocatalyzed insertion of metal carbenoids. This system is mild and robust, offering excellent selectivity across a broad range of substrates with high regio- and stereoselectivity. Furthermore, this strategy opens up vast opportunities for stereodivergent synthesis.

The construction of carbon-heteroatom bonds is one of the most active areas of research in organic chemistry because the function of organic molecules is often derived from the presence of heteroatoms. Although considerable advances have recently been achieved in radical-involved catalytic asymmetric C-N bond formation, there has been little progress in the corresponding C-O bond-forming processes. Here, we describe a photoinduced copper-catalyzed cross-coupling of readily available oxime esters and 1,3-dienes to generate diversely substituted allylic esters with high regio- and enantioselectivity (>75 examples; up to 95% ee). The reaction proceeds at room temperature under excitation by purple light-emitting diodes (LEDs) and features the use of a single, earth-abundant copper-based chiral catalyst as both the photoredox catalyst for radical generation and the source of asymmetric induction in C-O coupling. Combined experimental and density functional theory (DFT) computational studies suggest the formation of π-allylcopper complexes from redox-active oxime esters as bifunctional reagents and 1,3-dienes through a radical-polar crossover process.

In the presence of a catalytic amount of cobalt(II) acetylacetonate/Xantphos in combination with trimethylaluminum, various ketoalkenes underwent an intramolecular cyclization reaction triggered by cleavage of the allylic C(sp3)−H bond, affording carbocyclic compounds with high regio‐ and diastereoselectivity. Mono‐, bi‐, and tricarbocyclic compounds were produced in good yields. One of the products thus obtained was derivatized into tramadol in four simple steps. Notably, these intramolecular cyclizations took place in the absence of a gem‐disubstituent on the tethered carbon chain (without the Thorpe‐Ingold effect).magnified image

Welwitindolinone A Isonitrile 3 is the first of a family of oxindole natural products isolated from the cyanobacteria Hapalosiphon welwischii and Westiella intricate on the basis of their activity for reversing multiple drug resistance (MDR). A key transformation in the total synthesis of 3 reported (J. Am. Chem. Soc. 2008, 130, 2087) by John L. Wood, now at Colorado State University, was the chlorination of 1, that in one step established both the axial secondary chloro substituent and the flanking chiral quaternary center. The starting material for the synthesis of 3 was the diene acetonide 5, readily prepared from the Birch reduction product 4. Intermolecular ketene cycloaddition proceeded with high regio- and diastereoselectivity, to give the bicyclooctenone 6. The triazene-bearing Grignard reagent 7 added to the ketone 6 with the anticipated high diastereocontrol, to give, after reduction and protection, the cyclic urethane 8. Selective oxidation of the diol derived from 8 followed by silylation delivered the enone 9. Conjugate addition of hydride followed by enolate trapping gave the trifl ate 10. Pd-catalyzed meth-oxycarbonylation established the methyl ester 11. Addition of CH3MgBr to 11 gave 1, setting the stage for the establishment of the two key stereogenic centers of 2 and so of 3. The transformation of 1 to 2 was envisioned as being initiated by formation of a bridging chloronium ion. Pinacol-like 1,2-methyl migration then proceeded to form the trans diaxial product, moving the ketone-bearing branch equatorial. In addition to being an elegant solution of the problem of how to establish the axial chloro substituent of 3, this strategy might have some generality for the stereocontrolled construction of other alkylated cyclic quaternary centers. Reduction of the ketone 2 and dehydration of the resulting alcohol led, after deprotection and oxidation, to the ketone 12. Protection followed by β-elimination gave the enone 13. Direct reductive amination of 13 failed, but reduction of the methoxime was successful, giving, after acylation, the formamide 14. Reductive N-O bond cleavage followed by deprotection and isonitrile formation then set the stage for the planned intramolecular acylation to complete the synthesis of Welwitindolinone A Isonitrile 3.