Visible light-induced Pd catalysis typically operates through the transfer of a single electron. The resulting hybrid Pd radical species can participate in a range of radical-based transformations otherwise challenging or unknown via conventional 2-electron processes. This Minireview highlights the recent progress in this emerging area.
Visible light-induced Pd catalysis has emerged as a promising subfield of photocatalysis. The hybrid nature of Pd radical species has enabled a wide array of radical-based transformations otherwise challenging or unknown via conventional Pd chemistry. In parallel to the ongoing pursuit of alternative, readily available radical precursors, notable discoveries have demonstrated that photoexcitation can alter not only oxidative addition but also other elementary steps. This Minireview highlights the recent progress in this area.
Nature Communications, Published online: 09 November 2023; doi:10.1038/s41467-023-43136-y
The authors report a flow-cell system equipped with highly-electrolyte permeable Rh diffusion cathode for electrocatalytic hydrogenation of important bio-oil aromatic molecules at industrial-scale current densities.
Albert Eschenmoser, one of the greatest organic chemists of the past hundred years, died on July 14, 2023 at the age of 97. The extraordinary breadth of his scientific contributions ranged from synthetic methodology, structure elucidation, and synthesis of natural products to the chemical etiology of biomolecular structures.
Nature, Published online: 06 November 2023; doi:10.1038/d41586-023-03479-4
Tool based on machine learning uses features of writing style to distinguish between human and AI authors.Nature, Published online: 06 November 2023; doi:10.1038/d41586-023-03464-x
An unpublished analysis suggests that there are hundreds of thousands of bogus ‘paper-mill’ articles lurking in the literature.
Alkane-, arene-, and perfluoroalkanesulfonyl groups are widely used in organic synthesis to protect amino functionalities or to facilitate their installation. Protection of amino functions by a sulfonyl group to form sulfonamides is advantageous as they are easy to purify and tolerate various reaction conditions. On the other hand, sulfonyl group removal is difficult. Herein, we present a versatile metal-free photocatalytic reductive method for desulfonylation of sulfonamides and aryl sulfonates to the parent amines mediated by flavin derivatives, namely deazaisoalloxazines and deazaalloxazines, and visible light. Photocatalysis with 5-deazalloxazines is shown to even mediate the cleavage of perfluoroalkanesulfonamides (triflylamides and nonaflylamides), which is significantly more difficult than that of other sulfonamides and has previously not been achieved by photochemical means. The method is shown to perform consecutive desulfonylation and dealkylation of N-alkyl-N-phenylperfluoroalkanesulfonamides affording primary anilines. This occurs via consecutive reductive and oxidative catalytic cycles mediated by the flavin catalyst. The perfluoroalkylsulfonyl group fulfils a dual role serving as a protecting group and, after removal by the reductive cycle, as the species driving the oxidative dealkylation reaction.
Nature, Published online: 01 November 2023; doi:10.1038/d41586-023-03449-w
Gene expression reveals the story behind starfishes’ strange five-armed body plans
This review provides an overview of recent advances in Ni-metallaphotoredox Buchwald–Hartwig amination referring to the irradiation light covering ultraviolet, purple, blue, red, and white light as well as solar light.
The construction of C−N bonds is considered one of the most useful reactions in synthetic chemistry due to their widespread presence in pharmaceuticals, natural products, etc. Pd-catalyzed Buchwald–Hartwig amination (BHA) has provided the most efficient method to form (hetero)aryl amines but it required strong base and sophisticated ligands. In comparison, the combination of photocatalysis and nickel chemistry has revolutionized catalytic strategies and is emerging as a quintessence to realize BHA, termed as Ni-metallaphotoredox BHA. To pursue a universal protocol, diverse photocatalysts were designed and employed in Ni-metallaphotoredox BHA, and smoothly promoted C−N bond formations under irradiation of light from ultraviolet to red light, respectively. Note that the matching of photocatalyst and light was critical for success. Therefore, this review mainly focuses on the discussion of Ni-metallaphotoredox BHA according to the irradiation light's wavelength, covering ultraviolet, purple, blue, red, and white light as well as solar light. We try to find a clue in the relationship of structure-photophysical behaviors of photocatalysts under the same or different irradiation light. At last, current limitations and potential trends for advancing Ni-metallaphotoredox BHA are highlighted. We deem that it could encourage chemists to continue designing suitable photocatalyst for C−N bond formations under sunlight mimicking plants’ photosynthesis.
Open Access
  This article is licensed under a Creative Commons Attribution 3.0 Unported Licence.
Publication date: December 2023
Source: Molecular Catalysis, Volume 551
Author(s): Donglin Huang, Wulin Song, Hongmei Zhao, Meng Li, Liang Wei, Hongxi Zhang
The consequences of varying the substituent of the N atom in bidentate (P,PN) ligand was studied experimentally and theoretically within 3 series of palladium(II) complexes featuring also chlorides and/or isocyanides. The alkyl substituted complexes exhibit the higher stability while the H and trimethylsilyl containing counterparts were the most sensitive. For the latter, charge differences within the complexes were shown.
Three series of palladium(II) complexes supported by a phosphine-iminophosphorane ligand built upon an ortho-phenylene core were investigated to study the influence of the iminophosphorane N substituent. Cis-dichloride palladium(II) complexes 1 in which the N atom bears an isopropyl (iPr, 1 a), a phenyl (Ph, 1 b), a trimethylsilyl (TMS, 1 c) group or an H atom (1 d) were synthesized in high yield. They were characterized by NMR, IR spectroscopy, HR-mass spectrometry, elemental analysis, and X-ray diffraction. A substantial bond length difference between the Pd−Cl bonds was observed in 1. Complexes 1 a–d were converted into [Pd(LR)Cl(CN t Bu)](OTf)] 2 a–d whose isocyanide is located trans to the iminophosphorane. The corresponding dicationic complexes [Pd(LR)(CN t Bu)2](OTf)2 3 a–d were also synthesized, however they exhibited lower stability in solution than 2, the isopropyl derivative 3 a being the most stable of the series. Molecular modeling was performed to rationalize the regioselectivity of the substitution of the single chloride by isocyanide (from 1 to 2) and to study the electronic distribution in the complexes. In particular differences between the TMS and H containing complexes vs. the iPr and Ph ones were found. This suggests that the nature of the N substituent is far from innocent and can help tune the reactivity of iminophosphorane complexes.
Open Access  This article is licensed under a Creative Commons Attribution 3.0 Unported Licence.
Open Access  This article is licensed under a Creative Commons Attribution 3.0 Unported Licence.
Publication date: 11 January 2024
Source: Chem, Volume 10, Issue 1
Author(s): Hao Xu, Duo-Sheng Wang, Zhenyu Zhu, Arghya Deb, X. Peter Zhang
Synlett
DOI: 10.1055/a-2166-0400
A clean and efficient method has been developed for the introduction of benzylidene acetals into carbohydrate derivatives catalyzed by sulfonated graphene at room temperature. Yields were excellent in each case. The catalyst can be reused several times without much decrease in reactivity.
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Article in Thieme eJournals:
Table of contents | Abstract | Full text
Publication date: November 2023
Source: Molecular Catalysis, Volume 550
Author(s): Xi Li, Ying Xu, Kingdom Alorku, Jin Wang, Longlong Ma
With demand for lithium soaring due to its escalating use in energy applications, the heavier organosodium compounds have started to be considered as alternatives in synthesis. Recent reports have tackled their solubility problems, tamed their high reactivity and studied their intermediates constitution, accessing now transformations that were not possible with organolithiums, and opening new vistas for the use of these organosodium reagents.
With their highly reactive respective C−Na and N−Na bonds, organosodium and sodium amide reagents could be viewed as obvious replacements or even superior reagents to the popular, widely utilised organolithiums. However, they have seen very limited applications in synthesis due mainly to poor solubility in common solvents and their limited stability. That notwithstanding in recent years there has been a surge of interest in bringing these sustainable metal reagents into the forefront of organometallics in synthesis. Showcasing the growth in utilisation of organosodium complexes within several areas of synthetic chemistry, this Minireview discusses promising new methods that have been recently reported with the goal of taming these powerful reagents. Special emphasis is placed on coordination and aggregation effects in these reagents which can impart profound changes in their solubility and reactivity. Differences in observed reactivity between more nucleophilic aryl and alkyl sodium reagents and the less nucleophilic but highly basic sodium amides are discussed along with current mechanistic understanding of their reactivities. Overall, this review aims to inspire growth in this exciting field of research to allow for the integration of organosodium complexes within common important synthetic transformations.
Single-crystalline, plate-like Gd2Ti2O5S2 particles with atomically ordered surfaces loaded with ultrafine composite cocatalyst particles evolve H2 from an aqueous methanol solution with a remarkable apparent quantum efficiency (AQY) of 30 % at 420 nm.
Photocatalytic water splitting is a simple means of converting solar energy into storable hydrogen energy. Narrow-band gap oxysulfide photocatalysts have attracted much attention in this regard owing to the significant visible-light absorption and relatively high stability of these compounds. However, existing materials suffer from low efficiencies due to difficulties in synthesizing these oxysulfides with suitable degrees of crystallinity and particle sizes, and in constructing effective reaction sites. The present work demonstrates the production of a Gd2Ti2O5S2 (λ<650 nm) photocatalyst capable of efficiently driving photocatalytic reactions. Single-crystalline, plate-like Gd2Ti2O5S2 particles with atomically ordered surfaces were synthesized by flux and chemical etching methods. Ultrafine Pt-IrO2 cocatalyst particles that promoted hydrogen (H2) and oxygen (O2) evolution reactions were subsequently loaded on the Gd2Ti2O5S2 while ensuring an intimate contact by employing a microwave-heating technique. The optimized Gd2Ti2O5S2 was found to evolve H2 from an aqueous methanol solution with a remarkable apparent quantum efficiency of 30 % at 420 nm. This material was also stable during O2 evolution in the presence of a sacrificial reagent. The results presented herein demonstrates a highly efficient narrow-band gap oxysulfide photocatalyst with potential applications in practical solar hydrogen production.
A regioselective Ni-catalyzed Heck coupling, a reductive Heck coupling, and a Heck/Kumada coupling of light alkenes are reported herein. These strategies enable highly efficient hydro-arylation/-vinylation, (di)arylation, vinylation, and aryl-vinylation transformations thus accessing alkyl arenes and complex alkenes. This coupling strategy provides a modular and divergent platform for upgrading feedstock light alkenes.
Light olefins are abundantly manufactured in the petroleum industry and thus represent ideal starting materials for modern chemical synthesis. Selective and divergent transformations of feedstock light olefins to value-added chemicals are highly sought-after but remain challenging. Herein we report an exceptionally regioselective carbonickelation of light alkenes followed by in situ trapping with three types of nucleophiles, namely a reductant, base, or Grignard reagent. This protocol enables efficient 1,2-hydrofunctionalization, dicarbofunctionalization, and branched-selective Heck-type cross-coupling of light alkenes with aryl and alkenyl reagents to streamline access to diverse alkyl arenes and complex alkenes. Harnessing bulky N-heterocyclic carbene ligands with acenaphthyl backbones for nickel catalysts is crucial to attain high reactivity and selectivity. This strategy provides a rare, modular, and divergent platform for upgrading feedstock alkenes and is expected to find broad applications in medicinal chemistry and industrial processes.
The phase-dependent photoactivity of TiO2 materials represents a crucial factor for optimizing the efficiency of photocatalytic reactions. In this study, the distinct characteristics of the rutile and anatase phases were systematically explored, unveiling their interdependent influential roles in facilitating the selective photocatalytic reduction of 3-nitrophenol to 3-aminophenol. The underlying mechanisms responsible for these highlighted differences were uncovered and elucidated.
The photocatalytic selective reduction of 3-nitrophenol to 3-aminophenol was studied in the presence of titanium dioxide in the form of various anatase and rutile compositions. The reaction progress is altered by various parameters, which can be classified as intrinsic (depending on the chemical, structural, and electronic features) and extrinsic (depending on the reaction and conditions). The goal of the studies was to understand the influence of intrinsic factors and to compare the performance of anatase and rutile materials. The (photo)electrochemical analysis revealed unequivocally the differences in interfacial electron transfer, charge recombination, reduction driving force, and methanol photooxidation efficiency for titania polymorphs. It appeared that all mentioned processes were phase-dependent, and they contributed unequally to overall photocatalytic activity. In particular, methanol oxidation was the most efficient at the rutile phase, which overcame the critical limitation of the oxidation pathway and facilitated the reduction of 3-nitrophenol. On the other hand, the dark electron transfer efficiency was highest at the anatase phase, despite the lower driving force in this case. The presented thorough and systematic analysis of the discussed photocatalytic system (the photocatalyst and the reaction) should allow the rational design of efficient and selective photocatalysts.
Publication date: November 2023
Source: Molecular Catalysis, Volume 550
Author(s): Valery Zakharov, Yulia Kardasheva, Vladimir Chernyshev, Maria Terenina, Konstantin Kalmykov, Dmitry Ovsyannikov, Sergey Savilov, Svetlana Filippova, Edward Karakhanov, Sergey Dunaev, Leonid Aslanov
This review primarily revolves around the photochemical asymmetric three-component transformations facilitated by transition metal catalysis or organocatalysis. The intricate reaction mechanisms, diverse synthetic applications, and inherent limitations of these methods are thoroughly examined and discussed.
Over the past decades, asymmetric photochemical synthesis has garnered significant attention for its sustainability and unique ability to generate enantio-enriched molecules through distinct reaction pathways. Photochemical asymmetric three-component reactions have demonstrated significant potential for the rapid construction of chiral compounds with molecular diversity and complexity. However, noteworthy challenges persist, including the participation of high-energy intermediates such as radical species, difficulties in precise control of stereoselectivity, and the presence of competing background and side reactions. Recent breakthroughs have led to the development of sophisticated strategies in this field. This review explores the intricate mechanisms, synthetic applications, and limitations of these methods. We anticipate that it will contribute towards advancing asymmetric catalysis, photochemical synthesis, and green chemistry.
The review covers approaches to the sulfonamide synthesis that do not involve the use of sulfonyl halides. The methods are categorized according to the organosulfur building block used, i.e., S(II)-, S(IV)-, and S(VI)-containing compounds (thiols, sulfinates, activated sulfonic acid derivatives, etc.).
This review disclosed synthetic approaches to sulfonyl amides from non-sulfonyl halogenated precursors. Known methods were systematized into groups and subgroups according to the type of starting organosulfur compound. Thiols, disulfides, and sulfonamides form a group of S(II)-containing precursors, which are used in oxidative amination reactions. An important and versatile group for oxidative amination is represented with S(IV)-containing compounds, i. e., sufinates, sulfinamides, DMSO, N-sulfinyl-O-(tert-butyl)hydroxylamine, etc. A series of S(VI)-containing precursors for amination reactions (except sulfonyl halides) include sulfonic acids, sulfonyl azides, thiosulfonates, and sulfones. All approaches are represented with the most prominent examples of the resulting sulfonamides, which could be obtained in high yields mostly via short reaction sequences. Promising electrochemical methods for the preparation of sulfonamides from thiols, disulfides, sulfonamides, sulfinic acid derivatives, and dimethyl sulfoxide under mild and green conditions are also highlighted.
