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A binap-ligated copper iodide dimer embedded on a metal−organic framework (MOF) was designed as an effective photoredox catalyst by Dan Li, Jian He, and co-workers in their Research Article (e202300233). Under visible-light irradiation, this heterogenized copper(I) complex promotes multiple iminyl radical-mediated reactions initiated by N−O bond cleavage, with significantly enhanced photocatalytic activity compared to its homogeneous counterparts. The use of a hydroxamic acid linker for post-synthetic modification renders the catalyst recyclable.

A regioselective formal Tsuji–Trost β-allylation of various carbonyl compounds with different allylic electrophiles is reported. Reactions proceed through initial silyl enol ether formation and subsequent cooperative photoredox/nickel catalysis.

Abstract

The Tsuji–Trost reaction between carbonyl compounds and allylic precursors has been widely used in the synthesis of natural products and pharmaceutical compounds. As the α-C−H bond is far more acidic than the β-C−H bond, carbonyl compounds undergo highly regioselective allylation at the α-position and their β-allylation is therefore highly challenging. This innate α-reactivity conversely hampers diversity, especially if the corresponding β-allylation product is targeted. Herein, we present a formal intermolecular β-C−C bond formation reaction of a broad range of aldehydes and ketones with different allyl electrophiles through cooperative nickel and photoredox catalysis. β-Selectivity is achieved via initial transformation of the aldehydes and ketones to their corresponding silyl enol ethers. The overall transformation features mild conditions, excellent regioselectivity, wide functional group tolerance and high reaction efficiency. The introduced facile and regioselective β-allylation of carbonyl compounds proceeding through cooperative catalysis allows the preparation of valuable building blocks that are difficult to access from aldehydes and ketones using existing methodology.

Nature Chemistry, Published online: 24 April 2023; doi:10.1038/s41557-023-01195-0

Bifurcating the population as either verbal or visual thinkers is one of the simplest ways to classify intelligence. Bruce Gibb argues that visual thinking is key to chemistry, and that teaching and testing must focus on this type of thinking rather than traditional approaches promoting verbal thinking skills.

A tunable transformation including an enantioconvergent or a kinetic resolution step was used in the reaction of tertiary cyclobutenols with arylboroxines under a Ni/modified SPINOL catalytic system. This reaction allows the direct use of free hydroxyl groups as leaving groups while the strained ring remains untouched and provides enantioenriched cyclobutenes having a tertiary hydroxyl or an all-carbon quaternary stereocenter.

Abstract

We report that a nickel catalyst system with a modified 1,1′-spirobiindane-7,7′-diol-phosphoramidite (SPINOL) as the chiral ligand can enable the coupling of tertiary cyclobutenols and arylboroxines in an enantioconvergent manner, providing cyclobutenes with an all-carbon quaternary stereocenter in good yields (up to 84 % yield) with excellent enantioselectivities (up to >99 % ee). Moreover, the catalytic system can be applied in the kinetic resolution of cyclobutenols under slightly modified conditions, giving enantioenriched tertiary cyclobutenols with an s factor of up to >200. The reaction uses free hydroxyl groups as the leaving group without additional activation while the strained ring remains untouched. Preliminary mechanistic studies reveal that the inherent discrepant reactivity of the two enantiomers is the key to the controllable enantioconvergent and kinetic resolution process.

The formation of Si−Si bonds is an important transformation in organic synthesis. Herein, we present a unified electrochemical strategy for the efficient and selective synthesis of disilanes, oligosilanes, and cyclosilanes—which are important precursors for the synthesis of functional organic and polymeric compounds—from readily available chlorosilanes.

Abstract

Silanes are important compounds in industrial and synthetic chemistry. Here, we develop a general approach for the synthesis of disilanes as well as linear and cyclic oligosilanes via the reductive activation of readily available chlorosilanes. The efficient and selective generation of silyl anion intermediates, which are arduous to achieve by other means, allows for the synthesis of various novel oligosilanes by heterocoupling. In particular, this work presents a modular synthesis for a variety of functionalized cyclosilanes, which may give rise to materials with distinct properties from linear silanes but remain challenging synthetic targets. In comparison to the traditional Wurtz coupling, our method features milder conditions and improved chemoselectivity, broadening the functional groups that are compatible in oligosilane preparation. Computational studies support a mechanism whereby differential activation of sterically and electronically distinct chlorosilanes are achieved in an electrochemically driven radical-polar crossover mechanism.

The study reports selective electrochemical synthesis of 1H-indazoles and N-oxides, where electrochemical outcomes were dictated by the cathode material (RVC=reticulated vitreous carbon). The adaptability of 1H-indazole N-oxides for various C−H functionalization reactions was showcased. Furthermore, 1H-indazole N-oxides were utilized to synthesize the pharmaceutical molecules lificiguat and YD (3), key intermediates for various drugs, and a precursor for organic light-emitting diodes.

Abstract

The selective electrochemical synthesis of 1H-indazoles and their N-oxides and the subsequent C−H functionalization of the 1H-indazole N-oxides are described. The electrochemical outcomes were determined by the nature of the cathode material. When a reticulated vitreous carbon cathode was used, a wide range of 1H-indazole N-oxides were selectively synthesized, and the electrosynthesis products were deoxygenated to N-heteroaromatics, owing to cathodic cleavage of the N−O bond via paired electrolysis, when a Zn cathode was used. The scope of this electrochemical protocol is broad, as both electron-rich and electron-poor substrates were tolerated. The potency of this electrochemical strategy was demonstrated through the late-stage functionalization of various bioactive molecules, making this reaction attractive for the synthesis of 1H-indazole derivatives for pharmaceutical research and development. Detailed mechanistic investigations involving electron paramagnetic resonance spectroscopy and cyclic voltammetry suggested a radical pathway featuring iminoxyl radicals. Owing to the rich reactivity of 1H-indazole N-oxides, diverse C−H functionalization reactions were performed. We demonstrated the synthetic utility of 1H-indazole N-oxides by synthesizing the pharmaceutical molecules lificiguat and YD (3); key intermediates for bendazac, benzydamine, norepinephrine/serotonin reuptake inhibitors, SAM-531, and gamendazole analogues; and a precursor for organic light-emitting diodes.

Nature Communications, Published online: 22 April 2023; doi:10.1038/s41467-023-37965-0

Metal reductants show low efficiency in enantioselective nickel-catalyzed reductive cross-coupling of aryl aziridines with aryl iodides. Here, the authors improve the reaction efficiency through an electrochemical method.

The P-chelation assisted strategy to promote oxidative addition of C(sp²)−I bonds to gold has been extended to secondary phosphine oxides, but in contrast with related phosphines, a base (NEt₃, K₂CO₃) is needed. Back-donation prevails over donation in such oxidative additions. The reaction gives access to (P=O,C)-cyclometallated Au(III) complexes whose SPO moiety can be chemically derivatized.

Abstract

The coordination of secondary phosphine oxides (SPO) was shown to efficiently promote the activation of C(sp²)−I bonds by gold, as long as a base is added (NEt₃, K₂CO₃). These transformations stand as a new type of chelation-assisted oxidative addition to gold. The role of the base and the influence of the electronic properties of the P-ligand were analyzed computationally. Accordingly, the oxidative addition was found to be dominated by Au→(Ar−I) backdonation. In this case, gold behaves similarly to palladium, suggesting that the inverse electron flow reported previously (with prevailing (Ar−I)→Au donation, resulting in faster reactions of electron-enriched substrates) is a specific feature of electron-deficient cationic gold(I) complexes. The reaction gives straightforward access to (P=O,C)-cyclometallated Au(III) complexes. The possibility to chemically derivatize the SPO moiety at Au(III) was substantiated by protonation and silylation reactions.

Regiopure 1,6/7 perylenediimide (PDI) precursors are prepared at the gram scale for the first time, offering the possibility to systematically study the regioisomerism-dependant optoelectronic properties of PDI-based materials.

Abstract

The use of perylenediimide (PDI) building blocks in materials for organic electronic is of considerable interest. This popular n-type organic semiconductor is tuned by introducing peripheral groups in their ortho and bay positions. Such modifications radically alter their optoelectronic properties. In this article, we describe an efficient method to afford regioisomerically pure 1,6/7-(NO₂)₂- and (NH₂)₂-PDIs employing two key steps: the selective crystallization of 1,6-(NO₂)₂-perylene-3,4,9,10-tetracarboxy tetrabutylester and the nitration of regiopure 1,7-Br₂-PDI with silver nitrite. The optoelectronic properties of the resulting regioisomerically pure dinitro, diamino-PDIs and bisazacoronenediimides (BACDs) are reported and demonstrate the need to separate both regioisomers of such n-type organic semiconductors for their inclusion in advanced optoelectronic devices. For the first time, the two regioisomers of the same PDI starting material are available on the multigram scale, which will stimulate the exploration of regioisomerism/properties relationship for this family of dyes.

The synthesis and reactivity of a strictly T-shaped phosphine derived from an NNN acridane pincer ligand is reported. Phosphorus-centered reactivity towards nucleophiles and electrophiles is observed, and the activation of hydridic and protic E−H bonds is demonstrated, including complete disassembly of water.

Abstract

The steric tuning of a tridentate acridane-derived NNN pincer ligand allows for the isolation of a strictly T-shaped phosphine that exhibits ambiphilic reactivity. Well-defined phosphorus-centered reactivity towards nucleophiles and electrophiles is reported, contrasting with prior reports on this class of compounds. Reactions towards oxidants are also described. The latter result in the two-electron oxidation of the phosphorus atom from +III to +V and are accompanied by a strong geometric distortion of the NNN pincer ligand. By contrast, cooperative activation of E−H (HCl, HBcat, HOMe) bonds proceeds with retention of the phosphorus redox state. When using H₂O as a substrate, the reaction results in the full disassembly of H₂O to its constituent atoms, highlighting the potential of this platform for small molecule activation reactions.

CO₂ can be converted into hydrocarbon fuel through renewable electricity. This review introduces three strategies that can effectively combine CO₂ reduction with organic conversion. Through the selection of substrates and the design of catalysts, the construction of C−C, C−O, and C−N bonds can be precisely controlled, which can expand the product range and use renewable power more effectively.

Nature Communications, Published online: 07 April 2023; doi:10.1038/s41467-023-37620-8

Alkene epoxidation, whose products are important intermediates for the manufacture of pharmaceuticals and epoxy resins, has attracted extensive attention. Unlike the conventional electrochemical Br−/Br2-mediated epoxidation, here the authors report a photoelectrochemical Br−/BrO−- mediated system to achieve efficient epoxidation performance on α-Fe2O3.

Abstract

A practical electrochemical Minisci-type reaction for the synthesis of silylated heterocycles is described. Using N-hydroxyphthalimide (NHPI) as the hydrogen atom transfer (HAT) catalyst and trialkylsilanes as the silyl radical sources, a wide range of electron-deficient heterocycles in-cluding quinoline, quinoxaline, phthalazine, 3,6-dichloropyridazine, phenanthridine, 6-chloroimidazo[1,2-b]pyridazine and coumarin, etc. were easily converted to the corresponding silylated products in 37–83% yields.

Abstract

An electrochemical oxidative approach to spirooxazolidinones from phenol derivatives via intramolecular dearomative amination reactions is developed. This reaction proceeds without metal catalysts and external chemical oxidants, and shows broad substrate scope and diverse functional group compatibility. The synthetic utility of this strategy is further exhibited by the gram-scale synthesis and late-stage functionalization. By slightly tunning the reaction conditions, the alcohols (1°, 2° and 3°) can be afforded from phenol derivatives, which is a good strategy for the deprotection of para-methoxyphenyl (PMP) group to recover the alcohol function.

From activation to migration. Activation of a C−H bond of phenyl- and naphthyl-substituted isonitriles with heterocyclopentane-1,3-diylene represents a new method that allows the formation of benzo- and naphtho-azaphospholes. For this method, the absence of substituents in ortho-position of phenyl isonitriles is obligatory, but various substituents in other positions are tolerated. This aromatic substitution reaction can be strongly influenced by light and stoichiometry of the isonitrile used.

Abstract

Differently substituted phenyl isonitriles (with C−H bonds in ortho-position) and naphthyl isonitriles were reacted with the cyclic biradical [⋅P(μ-N-Ter)₂P⋅] (1). Insertion of the isonitrile formed a cyclic five-membered biradical [⋅P(NTer)₂C(R)P⋅] (2R, R=phenyl, naphthyl) in the first step, followed by C−H activation at the aryl substituent, resulting in novel azaphospholes (5R), which could be isolated and fully characterized. The formation of the azaphospholes can be prevented by the addition of a second equivalent of isonitrile, which causes the blocking of the radical centers in 2R by adduct formation (3R). Quantum mechanical calculations showed that a significant increase in the aromaticity of the benzo- and naphtho-azaphospholes is one of the driving forces for the activation process leading to the formation of thermodynamically favored azaphospholes. Targeted activation of C−H bonds using biradical systems represents a new synthetic approach to generate benzo- and naphtho-azaphospholes.