Search

The use of gem‐difluorinated cyclopropanes (gem‐DFCPs) as fluoroallyl surrogates under transition‐metal catalysis has drawn considerable attention recently but such reactions are restricted to producing achiral or racemic mono‐fluoroalkenes. Herein, we report the first enantioselective allylation of indoles under rhodium catalysis with gem‐DFCPs. This reaction shows exceptional branched regioselectivity towards rhodium catalysis with gem‐DFCPs, which provides an efficient route to enantioenriched fluoroallylated indoles with wide substrate scope and good functional group tolerance. [ABSTRACT FROM AUTHOR]

Transition-metal catalyzed allylic substitution reactions of alkenes are among the most efficient methods for synthesizing diene compounds, driven by the inherent preference for an inner-sphere mechanism. Here, we present a demonstration of an outer-sphere mechanism in Rh-catalyzed allylic substitution reaction of simple alkenes using gem-difluorinated cyclopropanes as allyl surrogates. This unconventional mechanism offers an opportunity for the fluorine recycling of gem-difluorinated cyclopropanes via C − F bond cleavage/reformation, ultimately delivering allylic carbofluorination products. The developed method tolerates a wide range of simple alkenes, providing access to secondary, tertiary fluorides and gem-difluorides with 100% atom economy. DFT calculations reveal that the C − C bond formation goes through an unusual outer-sphere nucleophilic substitution of the alkenes to the allyl-Rh species instead of migration insertion, and the generated carbon cation then forms the C − F bond with tetrafluoroborate as a fluoride shuttle. Allylic substitution reaction of alkenes has been well-developed, but it has limitations, partly due to the intrinsic predilection for an inner-sphere mechanism. Herein, the authors present an outer-sphere mechanism in Rh-catalyzed allylic substitution reaction of simple alkenes using gem-difluorinated cyclopropanes as allyl surrogates. [ABSTRACT FROM AUTHOR]

Direct synthesis of gem‐difluorinated carbocyclic molecules represents a longstanding challenge in organic chemistry. Herein, a Rh‐catalyzed [3+2] cycloaddition reaction between readily available gem‐difluorinated cyclopropanes (gem‐DFCPs) and internal olefins has been developed, enabling the efficient synthesis of gem‐difluorinated cyclopentanes with good functional group compatibility, excellent regioselectivity and good diastereoselectivity. The resulting gem‐difluorinated products can undergo downstream transformations to access various mono‐fluorinated cyclopentenes and cyclopentanes. This reaction demonstrates the use of gem‐DFCPs as a type of "CF2" C3 synthon for cycloaddition under transition metal catalysis, which provides potential strategy for synthesizing other gem‐difluorinated carbocyclic molecules. [ABSTRACT FROM AUTHOR]

As a special class of cyclopropanes, gem -difluorinated cyclopropanes have many fascinating properties as a result of the gem -difluoro substitution; thus, their reactions have received much attention from the synthetic chemistry community. Recently, gem -difluorinated cyclopropanes have gradually emerged as a type of novel and unique fluorinated allylic synthon in cross-coupling reactions for the synthesis of monofluoroalkenes. Herein, we briefly summarize recent advances in transition-metal-catalyzed reactions of gem -difluorinated cyclopropanes. 1 Introduction 2 Palladium-Catalyzed Reactions with Linear Selectivity 3 Palladium-Catalyzed Reactions with Branched Selectivity 4 Other Metal-Catalyzed Reactions 5 Conclusions [ABSTRACT FROM AUTHOR]

Efficient palladium recovery from high level liquid wastes (HLLW) is of increasing priority for sustainable development and addressing issues in radioactive waste treatment. However, searching for robust materials for palladium sorption, in the presence of large amounts of competing ions even at rather high acidity still poses a great challenge. Herein we present two novel cationic covalent triazine frameworks (denoted as CTF-S and CTF-L) created by polymerization of monomers IL-S and IL-L for palladium recovery. The resultant CTF-S and CTF-L with respective surface areas of 212.9 m2 g−1 and 342.5 m2 g−1 exhibit excellent sorption ability toward palladium at high acidity. This has been demonstrated by a maximum sorption capacity of 333 mg g−1, which is the highest at 3 M HNO3 among all porous adsorbents reported so far. More importantly, these materials reveal remarkable selectivity toward palladium over other metal ions that are co-existing in simulated HLLW. In addition, thanks to the relatively large π-conjugated structures, no obvious decrease in sorption capability was observed after being exposed to 1000 kGy γ irradiation. Desorption could be easily achieved by a single contact with a mixed solution of 1 M thiourea and 1 M HCl and the sorption performance still remains at the initial level without conspicuous loss after five cycles. The XPS results, anion competitive experiments, and DFT calculations propose a sorption mechanism in which the anion exchange between anionic Pd complexes and chloride, and the chemical coordination between triazine N and Pd(II) work coorperatively to enhance the sorption capacity. This work not only provides a new kind of excellent adsorbent for selective palladium recovery, but also demonstrates a promising approach for constructing robust materials for nuclear waste remediation. [ABSTRACT FROM AUTHOR]

Gem -difluorinated cyclopropanes have become an important type of allyl surrogate in transition-metal-catalyzed ring-opening processes, as demonstrated recently through various important advances, especially with palladium catalysis. The versatile fluorinated allyl species generated in this way from gem -difluorinated cyclopropanes exhibit unique advantages compared with conventional allyl sources. By using gem -difluorinated cyclopropanes as allyl surrogates, we achieved a direct allylation of simple arenes through rhodium catalysis under mild conditions. This transformation permits directing-group-free allylation of simple arenes, including electron-neutral, electron-rich, and electron-deficient ones. Here, we give a brief introduction to this area and we discuss our thoughts regarding our recent work and its design. 1 Introduction 2 Our Design 3 Condition Optimization and Substrate Scope 4 Applications in Synthesis 5 Mechanistic Discussions 6 Conclusion and Outlook [ABSTRACT FROM AUTHOR]

The recovery of lanthanides from high level liquid waste (HLLW) is of great significance for both environmental protection and sustainable development of resources. Traditional methods for this purpose are often plagued by poor selectivity, low capacity, and limited acid tolerance. Here we report a new material prepared by impregnating P[5]A-DGA onto porous Amberlite XAD-7 resin for efficient and selective lanthanide adsorption from highly acidic solutions. The as-prepared composite material (PDA resin) shows outstanding sorption efficiency for lanthanides in a wide range of acidities (0.01–3 M HNO 3) and exhibits good selectivity towards lanthanides over different kinds of competing metal ions in simulated nuclear wastewater. Adsorption equilibrium can be achieved within 60 min and the pseudo-second-order model shows better correlation with the kinetic data, indicating that chemical adsorption is the rate determining step. Adsorption isotherm data can be well fitted by Langmuir model, giving a Eu(III) sorption capacity of 33.3 mg/g at 1 M HNO 3 , which is superior to other materials employed for the similar purpose. Importantly, the adsorption capacity can be regenerated by using a mixture of 1 M guanidine carbonate and 0.05 M EDTA-2Na solution as the eluent, and the lanthanide adsorption efficiency from simulated nuclear wastewater remains at the initial level after three desorption-adsorption cycles. Finally, the possible configurations of the ligand-Ln(III) complexes were optimized by DFT calculations, which suggest that each Ln(III) tends to bind to three DGA arms via a nine coordination mode. This research advances the development of pillar[5]arenes for lanthanide recovery by demonstrating a simple and generally applicable method to convert P[5]A-DGA extractant into an efficient adsorbent. [Display omitted] • The first pillar[5]arene-based ligand impregnated resin (PDA) was prepared. • The maximum adsorption capacity for Eu was as high as 33.3 mg/g at 1 M HNO 3. • It can operate in a wide range of acidity (0.01–3 M HNO 3) with good performance. • Simulated nuclear wastewater experiments indicate good selectivity for lanthanides. • PDA resin can be reused for three cycles without decrease in sorption efficiency. [ABSTRACT FROM AUTHOR]

Small-ring chemistry is a fascinating field in organic chemistry. gem -Difluorinated cyclopropanes, a unique class of cyclopropanes, have garnered significant interest due to their intrinsic high reactivity. In this context, gem -difluorinated cyclopropanes have been extensively investigated as fluoroallylic synthons in Pd-catalyzed ring-opening/cross-coupling reactions for the synthesis of monofluoroalkenes with linear or branched selectivity. In contrast, Rh-catalysis has revealed diverse selectivity in the reaction of gem -difluorinated cyclopropanes, such as regioselectivity, enantioselectivity, and chemoselectivity. This feature article aims to summarize our efforts towards developing Rh-catalyzed reactions of gem -difluorinated cyclopropanes, briefly discussing the design, selectivity, reaction mechanisms and future research prospects.

Enhancers are a class of cis -regulatory elements in the genome that instruct the spatiotemporal transcriptional program. Last decade has witnessed an exploration of non-coding transcripts pervasively transcribed from active enhancers in diverse contexts, referred to as enhancer RNAs (eRNAs). Emerging evidence unequivocally suggests eRNAs are an important layer in transcriptional regulation. In this mini-review, we summarize the well-established regulatory models for eRNA actions and highlight the recent insights into the structure and chemical modifications of eRNAs underlying their functions. We also explore the potential roles of eRNAs in transcriptional condensates., Competing Interests: The authors declare that the research was conducted in the absence of any commercial or financial relationships that could be construed as a potential conflict of interest., (Copyright © 2023 Chen, Zeng, Kang, Hu, Li, Sun and Zhao.)