Recent Advances in Deuteration Reactions

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Recent Advances in Deuteration Reactions†


Comprehensive Summary

The deuteration of organic compounds has attracted more attentions in recent years for the potential applications in new drug discovery and synthetic chemistry. For this purpose, many efficient deuterium labeling methodologies have been developed, including hydrogen isotope exchange (HIE), reductive deuteration, and dehalogenative deuteration that allow for the synthesis of selectively deuterated compounds. In the last few years, great breakthroughs in selective isotope labeling have been achieved and the interest in new methodologies for the deuteration of organic molecules is rising. In this review, we summarized the recent developments in the selective deuteration of organic molecules since 2021. Several types of key processes in deuterium incorporation reactions, including H/D exchange, reductive deuteration and dehalogenative deuteration, are introduced and discussed.

Key Scientists

In the 2000s, Derdau and Atzrodt's group have made great contributions to the directing group assisted noble-metal catalyzed hydrogen isotope exchange of arenes and applications of labeled compounds. During the same period, Sajiki and co-workers completed a series of deuteration reactions by heterogeneous platinum-group metal catalysts. Since 2015, Gregory Pieters and co-workers have developed ruthenium catalysts for selective hydrogen isotope exchange. In 2016, Chirik's group achieved hydrogen isotope exchange in the presence of a homogeneous iron complex. David MacMillan and coworkers have made breakthroughs in photocatalyzed HIE reactions for α-amino C(sp3)–H bonds. From 2020, a series of nanoelectrodes were designed for selective dehalogenative deuterations and reductive deuteration of unactivated unsaturated bonds by Zhang's group. Recently, Beller's group developed several efficient strategies for isotopic labeling using heterogeneous earth-abundant catalysts. Our review summarized the latest and important developments since 2021.

Organic Synthesis through Radical Innovation: Frustrated Radical Pairs

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Organic Synthesis through Radical Innovation: Frustrated Radical Pairs†

Recent developments have led to the emergence of Frustrated Radical Pairs (FRPs) as an extension of the radical family. FRPs are formed from FLPs through Single Electron Transfer (SET) and exhibit the ability to activate a variety of chemical bonds. This review highlights the current state of FRPs in organic synthesis, delves into mechanistic insights, explores their potential, and underscores the challenges in this emerging field.


Abstract

Frustrated Lewis Pairs (FLPs) represent a unique class of interactions in Lewis acid-base chemistry, driven by spatial hindrance or incongruent orbital energy levels that hinder the formation of effective coordination bonds. FLPs have received significant attention for their application in activating small molecules and facilitating organic synthesis reactions. Recent developments have led to the emergence of Frustrated Radical Pairs (FRPs) as an extension of the radical family. FRPs are formed from FLPs through Single Electron Transfer (SET) and exhibit the ability to activate a variety of chemical bonds. While research on FLPs is well-established, investigations into FRPs in organic reactions remain limited. This review highlights the current state of FRPs in organic synthesis, delves into mechanistic insights, explores their potential, and underscores the challenges in this emerging field.

From Phenols to Antimicrobial Phenazines: Tyrosinase‐like Catalytic Activity of a Bisguanidine Based Bis(μ‐oxido) Complex

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From Phenols to Antimicrobial Phenazines: Tyrosinase-like Catalytic Activity of a Bisguanidine Based Bis(μ-oxido) Complex

Complex phenolic derivatives like naphthols, quinolinols and indolols are converted via a catalytic oxygenation reaction using a bisguanidine stabilized oxido complex as catalyst. Subsequent condensation with 1,2-phenylendiamine results in phenazines products which function as biological antimicrobial agents against bacteria.


Abstract

The catalytically active center of the enzyme tyrosinase, standing out for its unusual substrate diversity, consists of a side-on μ-η2:η2-peroxido complex ( S P). Several ligand systems stabilizing a S P and able to mimic the catalytic activity of the enzyme towards simple phenolic substrates are known. Only a few catalytically active systems based on the isoelectronic isomer structure of S P, a bis(μ-oxido)dicopper(III) complex (O), were investigated until now. Two years ago, we presented with the TMGbenza a hybrid guanidine based tyrosinase model system stabilizing an O species with an exceptional substrate diversity. Herein we studied the catalytic activity of another O species stabilized by the bisguanidine ligand TMG2tol. The reaction conditions for the catalytic oxygenation were optimized and a broad spectrum of phenolic substrates like naphthol, quinolinols and indolols was tested. Naturally occurring phenazine derivatives like phenazine-1-carboxylamide (PCN) and phenazine-1-carboxylic acid (PCA) show antifungal as well as antibacterial activity, functioning as biological control agents against crop disease like take-all. Hence, the synthesized phenazines were evaluated for their potential antimicrobial activities against representative gram-positive and gram-negative bacteria.

A Water‐Stable Europium Metal‐Organic Framework as a Turn‐Off Fluorescence Sensor for Ascorbic Acid Detection in Human Serum

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A Water-Stable Europium Metal-Organic Framework as a Turn-Off Fluorescence Sensor for Ascorbic Acid Detection in Human Serum

A turn-off fluorescence sensor of Eu-NDBC exhibits a rapid quenching to ascorbic acid, which can accurately monitor ascorbic acid in human serum.


Abstract

Ascorbic acid (AA) is a biomarker of some nervous system diseases, whose detection is of significance in many fields. The hydrothermal reaction of naphthalene-2,6-dicarboxylic acid (H2NDBC) with Eu3+ produced a europium MOF, Eu-NDBC. Eu-NDBC emits the combined emissions from the intraligand charge transfer (ILCT) of NDBC2− ligand and 5D0→7Fj (j=1–4) transfers of Eu(III). The factors of MOF dosage, pH and fluorescence response time are optimized as 0.6 mg, 7.35, and 5 min respectively. The sensitivity test shows a linear fitting equation of I0/I=0.00239 ⋅ CAA+1.03774 (CAA=AA concentration), with its limit of detection calculated as 4.53 μM in a wide linear range of 0–900 μM. The linear fitting of Stern-Volmer equation gives KSV=2.46×103 M−1 and Kq=4.96×106 M−1 S−1, suggesting Eu-NDBC sensing AA is a dynamic fluorescence quenching process. Nine control amino acids can't affect Eu-NDBC sensing AA and the emission intensity stay stable in five fluorescence quenching-recovery cycles. The returned CAA closed to the set CAA and the recoveries around 100 % support the accurate AA detection by Eu-NDBC in human serum. Totally, Eu-NDBC can be regarded as a quantitative turn-off fluorescence sensor to AA with high sensitivity and selectivity, rapid response and durability.

Palladium‐Catalyzed Cyclization/Alkenylation of Ynone Oximes with Vinylsilanes for the Assembly of Isoxazolyl Vinylsilanes

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Palladium-Catalyzed Cyclization/Alkenylation of Ynone Oximes with Vinylsilanes for the Assembly of Isoxazolyl Vinylsilanes

A novel and efficient palladium-catalyzed cascad cyclization/alkenylation of ynone oximes with various vinylsilane agents for the assembly of synthetically valuable isoxazolyl vinylsilane derivative has been accomplished. Under the optimized conditions, a wide array of ynone oximes can be efficiently converted into the isoxazolyl vinylsilanes in moderate to good yields with eminent functional group compatibility.


Abstract

A palladium-catalyzed cascade cyclization/alkenylation for the assembly of synthetically valuable isoxazolyl vinylsilane derivative has been accomplished. Easily accessible ynone oximes, and available vinylsilane agents were used as the reaction starting materials This protocol features broad substrate scope, good functional group tolerance, and good step- and atom-economy. Remarkably, this approach provides a new approach for the construction of structurally diverse isoxazolyl-containing vinylsilanes with high molecular complexity, showing a promising application in synthetic and pharmaceutical chemistry.

Investigating Surgical Mask Thermal Degradation via X‐Ray Techniques for Efficient Reuse

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The Covid-19 crisis has led to a massive surge in the use of surgical masks worldwide, causing risks of shortages and high pollution. Reusing the masks may be promising to reduce such risks, especially since various decontamination techniques are being investigated. In this study, the thermal degradation of surgical masks was investigated using X-ray-based techniques such as XRD and XPS. Additional characterization was performed using scanning electron microscopy and contact angle measurements. XRD experiments reveal an increase in both crystal size and crystallinity of the mask with temperature until it is destroyed at 160°C. However, XPS results show that there was no significant change in the surface chemistry of the mask, as no other chemical element has been detected in the mask heated up. Breathability has been proven compliant with standards until 150°C.

Planar Chiral Ferrocendiyl and Ruthenocendiyl Bisimidazoline Bispalladacycles Featuring Pyridin‐2‐olates and Ketophenolates as Potentially Hemilabile Ligands in Asymmetric 1,4‐Additions

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Planar Chiral Ferrocendiyl and Ruthenocendiyl Bisimidazoline Bispalladacycles Featuring Pyridin-2-olates and Ketophenolates as Potentially Hemilabile Ligands in Asymmetric 1,4-Additions

The coordination of pyridonates and a ketophenolate to metallocene based bispalladacycles is reported. Using the phenolate ligand in a catalytic asymmetric 1,4-addition, higher activity than with the benchmark system from literature was found, while the pyridonate decreased the activity. The different μ2- and κ2-coordination modes are discussed as reason.


Abstract

Planar chiral bispalladacycles based on ferrocene have previously been shown to be excellent catalysts for asymmetric 1,4-additions of α-cyanoacetates to enones. For a bimetallic reaction pathway, it was found that product decomplexation is probably rate-determining as a result of a bimetallic two-point binding. We hypothesized that the use of hemilabile chelating ligands might accelerate this step to improve the catalytic activity. Here we report the use of pyridin-2-olates (pyridonates) as potentially hemilabile 1,3-N,O-chelating ligands in this catalytic application. In this article, we describe the first coordination of pyridonate ligands to planar chiral, metallocene based palladacycles. Four of the resulting ferrocene and ruthenocene bis-palladium complexes were characterized by X-ray single crystal structure analysis revealing a μ2-(O,N) coordination mode. We suggest that an observed lower catalytic efficiency of the new complexes has its origin in this particular coordination mode. For that reason, a related trifluoromethylketophenolate ligand was installed for which κ2-(O,N) coordination was expected and also experimentally found. Indeed, in that case catalytic activity was improved compared to the benchmark system.