High Deuterium Incorporation Research Articles

Hydrodeuteroalkylation of Unactivated Olefins Using Thianthrenium Salts

AbstractIsotopically labeled alkanes play a crucial role in organic and pharmaceutical chemistry. While some deuterated methylating agents are readily available, the limited accessibility of other deuteroalkyl reagents has hindered the synthesis of corresponding products. In this study, we introduce a nickel‐catalyzed system that facilitates the synthesis of various deuterium‐labeled alkanes through the hydrodeuteroalkylation of d2‐labeled alkyl TT salts with unactivated alkenes. Diverging from traditional deuterated alkyl reagents, alkyl thianthrenium (TT) salts can effectively and selectively introduce deuterium at α position of alkyl chains using D2O as the deuterium source via a single‐step pH‐dependent hydrogen isotope exchange (HIE). Our method allows for high deuterium incorporation, and offers precise control over the site of deuterium insertion within an alkyl chain. This technique proves to be invaluable for the synthesis of various deuterium‐labeled compounds, especially those of pharmaceutical relevance.

Hydrodeuteroalkylation of Unactivated Olefins Using Thianthrenium Salts.

Isotopically labeled alkanes play a crucial role in organic and pharmaceutical chemistry. While some deuterated methylating agents are readily available, the limited accessibility of other deuteroalkyl reagents has hindered the synthesis of corresponding products. In this study, we introduce a nickel-catalyzed system that facilitates the synthesis of various deuterium-labeled alkanes through the hydrodeuteroalkylation of d2-labeled alkyl TT salts with unactivated alkenes. Diverging from traditional deuterated alkyl reagents, alkyl thianthrenium (TT) salts can effectively and selectively introduce deuterium at α position of alkyl chains using D2O as the deuterium source via a single-step pH-dependent hydrogen isotope exchange (HIE). Our method allows for high deuterium incorporation, and offers precise control over the site of deuterium insertion within an alkyl chain. This technique proves to be invaluable for the synthesis of various deuterium-labeled compounds, especially those of pharmaceutical relevance.

Rapid (Deuterio)difluoromethylation of Heteroatoms using R‐22 Gas: A Demonstration of Flow Chemistry in Suppressing Intrinsic Reaction Pathways

The exploration and use of deuteriodifluoromethyl heteroatom groups (X‐CF2D) has been limited by persistent challenges, including the unavailability of CF2D precursor reagents, as well as safety, scalability, and environmental concerns associated with conventional batch‐mode syntheses. In this study, we report the use of atom‐efficient and cost‐effective R‐22 gas (ClCF2H) in continuous flow for the rapid installation of CF2H and CF2D groups on heteroatom centers. However, the intrinsic nucleophilic substitution between heteroatom anions and ClCF2H decreases the deuterium incorporation levels. Notably, a judiciously designed continuous flow system proves to suppress the previously unavoidable SN2 reaction and allows for the selective carbene coupling to generate X‐CF2D products with high deuterium incorporation levels up to 96%. Our continuous flow systems provide a broad scope of X‐CF2H and X‐CF2D products (X = S, O, N) within a short residence time of 5 minutes and scalability is also demonstrated.

Metallaphotoredox deuteroalkylation utilizing thianthrenium salts

Deuterium labeling compounds play a crucial role in organic and pharmaceutical chemistry. The synthesis of such compounds typically involves deuterated building blocks, allowing for the incorporation of deuterium atoms and functional groups into a target molecule in a single step. Unfortunately, the limited availability of synthetic approaches to deuterated synthons has impeded progress in this field. Here, we present an approach utilizing alkyl-substituted thianthrenium salts that efficiently and selectively introduce deuterium at the α position of alkyl chains through a pH-dependent HIE process, using D2O as the deuterium source. The resulting α-deuterated alkyl thianthrenium salts, which bear two deuterium atoms, exhibit excellent selectivity and deuterium incorporation in electrophilic substitution reactions. Through in situ formation of isotopically labelled alkyl halides, these thianthrenium salts demonstrate excellent compatibility in a series of metallaphotoredox cross-electrophile coupling with (hetero)aryl, alkenyl, alkyl bromides, and other alkyl thianthrenium salts. Our technique allows for a wide range of substrates, high deuterium incorporation, and precise control over the site of deuterium insertion within a molecule such as the benzyl position, allylic position, or any alkyl chain in between, as well as neighboring heteroatoms. This makes it invaluable for synthesizing various deuterium-labeled compounds, especially those with pharmaceutical significance.

Mechanical-Force-Induced Non-spontaneous Dehalogenative Deuteration of Aromatic Iodides Enabled by Using Piezoelectric Materials as a Redox Catalyst.

The development of green and efficient deuteration methods is of great significance for various fields such as organic synthesis, analytical chemistry, and medicinal chemistry. Herein, we have developed a dehalogenative deuteration strategy using piezoelectric materials as catalysts in a solid-phase system under ball-milling conditions. This non-spontaneous reaction is induced by mechanical force. D2O can serve as both a deuterium source and an electron donor in the transformation, eliminating the need for additional stoichiometric exogenous reductants. A series of (hetero)aryl iodides can be transformed into deuterated products with high deuterium incorporation. This method not only effectively overcomes existing synthetic challenges but can also be used for deuterium labelling of drug molecules and derivatives. Bioactivity experiments with deuterated drug molecule suggest that the D-ipriflavone enhances the inhibitory effects on osteoclast differentiation of BMDMs in vitro.

Mechanical‐Force‐Induced Non‐spontaneous Dehalogenative Deuteration of Aromatic Iodides Enabled by Using Piezoelectric Materials as a Redox Catalyst

AbstractThe development of green and efficient deuteration methods is of great significance for various fields such as organic synthesis, analytical chemistry, and medicinal chemistry. Herein, we have developed a dehalogenative deuteration strategy using piezoelectric materials as catalysts in a solid‐phase system under ball‐milling conditions. This non‐spontaneous reaction is induced by mechanical force. D2O can serve as both a deuterium source and an electron donor in the transformation, eliminating the need for additional stoichiometric exogenous reductants. A series of (hetero)aryl iodides can be transformed into deuterated products with high deuterium incorporation. This method not only effectively overcomes existing synthetic challenges but can also be used for deuterium labelling of drug molecules and derivatives. Bioactivity experiments with deuterated drug molecule suggest that the D‐ipriflavone enhances the inhibitory effects on osteoclast differentiation of BMDMs in vitro.

Palladium-Catalyzed Deuteration of Arylketone Oxime Ethers.

We report herein the development of palladium-catalyzed deacylative deuteration of arylketone oxime ethers. This protocol features excellent functional group tolerance, heterocyclic compatibility, and high deuterium incorporation levels. Regioselective deuteration of some biologically important drugs and natural products are showcased via Friedel-Crafts acylation and subsequent deacylative deuteration. Vicinal meta-C-H bond functionalization (including fluorination, arylation, and alkylation) and para-C-H bond deuteration of electro-rich arenes are realized by using the ketone as both directing group and leaving group, which is distinct from aryl halide in conventional dehalogenative deuteration.

Palladium‐Catalyzed Deuteration of Arylketone Oxime Ethers

AbstractWe report herein the development of palladium‐catalyzed deacylative deuteration of arylketone oxime ethers. This protocol features excellent functional group tolerance, heterocyclic compatibility, and high deuterium incorporation levels. Regioselective deuteration of some biologically important drugs and natural products are showcased via Friedel–Crafts acylation and subsequent deacylative deuteration. Vicinal meta‐C−H bond functionalization (including fluorination, arylation, and alkylation) and para‐C−H bond deuteration of electro‐rich arenes are realized by using the ketone as both directing group and leaving group, which is distinct from aryl halide in conventional dehalogenative deuteration.

Photocatalytic Dehalogenative Deuteration of Halides over a Robust Metal-Organic Framework.

Deuterium labelling of organic compounds is an important process in chemistry. We report the first example of photocatalytic dehalogenative deuteration of both arylhalides and alkylhalides (40 substrates) over a metal-organic framework, MFM-300(Cr), using CD3 CN as the deuterium source at room temperature. MFM-300(Cr) catalyses high deuterium incorporation and shows excellent tolerance to various functional groups. Synchrotron X-ray powder diffraction reveals the activation of halogenated substrates via confined binding within MFM-300(Cr). In situ electron paramagnetic resonance spectroscopy confirms the formation of carbon-based radicals as intermediates and reveals the reaction pathway. This protocol removes the use of precious-metal catalysts from state-of-the-art processes based upon direct hydrogen isotope exchange and shows high photocatalytic stability, thus enabling multiple catalytic cycles.

Photocatalytic Dehalogenative Deuteration of Halides over a Robust Metal–Organic Framework

AbstractDeuterium labelling of organic compounds is an important process in chemistry. We report the first example of photocatalytic dehalogenative deuteration of both arylhalides and alkylhalides (40 substrates) over a metal–organic framework, MFM‐300(Cr), using CD3CN as the deuterium source at room temperature. MFM‐300(Cr) catalyses high deuterium incorporation and shows excellent tolerance to various functional groups. Synchrotron X‐ray powder diffraction reveals the activation of halogenated substrates via confined binding within MFM‐300(Cr). In situ electron paramagnetic resonance spectroscopy confirms the formation of carbon‐based radicals as intermediates and reveals the reaction pathway. This protocol removes the use of precious‐metal catalysts from state‐of‐the‐art processes based upon direct hydrogen isotope exchange and shows high photocatalytic stability, thus enabling multiple catalytic cycles.

B(C6F5)3-Catalyzed Intramolecular Hydroalkoxylation Deuteration Reactions of Unactivated Alkynyl Alcohols.

Using D2O as a deuterium source, a method for the deuteration of intra- and extra-cyclic methylene has been developed for cyclic ethers with moderate yield and excellent deuterium incorporation. This transformation features superb functional group tolerance in a wide range of alkynols. Notably, the critical factor to achieve high deuterium incorporation is determined by the hydrogen isotope exchange reaction of an unstable oxonium ion. This novel methodology provides an efficient and concise synthetic route to a number of valuable deuterated cyclic ethers that are often difficult to prepare with other methods.

Visible-Light-Induced Reductive Coupling of Arylacetylenes with Benzothiazole Sulfones.

In this study, we propose heavy-metal-free reductive coupling of arylacetylenes with benzothiazole sulfones. The reactions of alkyl or benzylic benzothiazole sulfones with arylacetylenes are successfully performed in the presence of Hantzsch esters and K2CO3 under visible-light irradiation to afford 1,2-disubstituted alkenes in moderate to good yields, with Z-isomer as the major product. The utility of this protocol is expanded to α-deuterative coupling using a deuterated Hantzsch ester, furnishing the corresponding alkenes with high deuterium incorporation.

Distal p-benzylic deuteration via N-heterocyclic carbene catalyzed ring opening of p-cyclopropylbenzaldehydes.

Deuterium incorporation at selective sites of organic compounds has long attracted the interest of the pharmaceutical industry. Here, we present a distal p-benzylic deuteration via N-heterocyclic carbene catalyzed ring-opening of cyclopropylbenzaldehydes with MeOD as the deuterium source. The corresponding 4-alkylbenzoates with high deuterium incorporation at the benzylic position were obtained in good yields. The stable benzylic deuterium remained intact for further chemical transformations.

Transition metal-free photocatalytic reductive deuteration of ketone derivatives

Deuterium labelling techniques have shown widespread applications in organic synthesis, analytic chemistry, life science and material science. The design of practical deuteration reactions which is environmentally friendly is highly desired for pharmaceutical development and industrial processes while remaining underexplored. We herein report a convenient, transition metal-free strategy for reductive deuteration of ketone derivatives to α-deuterated alcohols by employing a conjugated aryl amine-based organophotocatalyst, a dipropyl disulfide co-catalyst and an inorganic reductant. Upon irradiation with visible light and under an air atmosphere, a variety of diaryl ketones, heteroaryl ketones, cyclic ketones, α-ketoesters, benzil derivatives, aliphatic ketones and drug-like molecules were converted into corresponding α-deuterated aryl alcohols in good to excellent yields and with high deuterium incorporation (up to 99% D-incorporation). Only low toxic side-products, such as sodium salts and carbon dioxide, were generated. Consequently, the synthetic utility of this method is highlighted by the preparation of several D-labeled drug-like molecules, including orphenadrine, carbinoxamine and modafinil.

Manganese-Catalysed Deuterium Labelling of Anilines and Electron-Rich (Hetero)Arenes.

There is a constant need for deuterium‐labelled products for multiple applications in life sciences and beyond. Here, a new class of heterogeneous catalysts is reported for practical deuterium incorporation in anilines, phenols, and heterocyclic substrates. The optimal material can be conveniently synthesised and allows for high deuterium incorporation using deuterium oxide as isotope source. This new catalyst has been fully characterised and successfully applied to the labelling of natural products as well as marketed drugs.

Manganese‐Catalysed Deuterium Labelling of Anilines and Electron‐Rich (Hetero)Arenes

AbstractThere is a constant need for deuterium‐labelled products for multiple applications in life sciences and beyond. Here, a new class of heterogeneous catalysts is reported for practical deuterium incorporation in anilines, phenols, and heterocyclic substrates. The optimal material can be conveniently synthesised and allows for high deuterium incorporation using deuterium oxide as isotope source. This new catalyst has been fully characterised and successfully applied to the labelling of natural products as well as marketed drugs.

A Reductive Deuteration Approach to the Efficient Synthesis of Deuterated Polymers

AbstractDeuterated polymers have wide applications but limited synthetic methods. In this study, we report an efficient two-step approach for the synthesis of deuterated polyesters and polyurethanes. Firstly, two practical single-electron transfer (SET) reductive-deuteration methods have been developed for site-selective introduction of C(sp3)–D into diol monomers. Nine deuterated diol monomers with high deuterium incorporations were synthesized under SmI2–D2O and/or Na-EtOD-d 1 SET reductive-deuteration conditions. Then, six typical deuterated polyesters and polyurethanes were synthesized using those deuterated monomers under typical polymerization conditions. In all the synthesized polymers, high deuterium incorporation was fully maintained, which showcased the potential application of this approach for the synthesis of polymers with site-specific deuterium labelling.

A bench-stable reagent for C-4 selective deuteriodifluoromethylation of azines

Deuteriodifluoromethyl (CF2D) is a challenging and important functional group due to difficult deuterium incorporation and lack of effective precursor reagents. Herein, we report a bench-stable reagent, deuteriodifluoromethyl phosphine (DDFP) from cheap deuterium source for selectivity deuteriodifluoromethylation of azines with a high deuterium incorporation yield. The late-stage modification of complex molecules further confirmed the potential of this reagent for practical applications. We expect that our reagent to find applications in synthesis of isotope-labelled molecules of interests for drug-discovery and related ilucidation of mechanism of action.

Catalytic asymmetric synthesis of enantioenriched α-deuterated pyrrolidine derivatives.

The recent promising applications of deuterium-labeled pharmaceutical compounds have led to an urgent need for the efficient synthetic methodologies that site-specifically incorporate a deuterium atom into bioactive molecules. Nevertheless, precisely building a deuterium-containing stereogenic center, which meets the requirement for optimizing the absorption, distribution, metabolism, excretion and toxicity (ADMET) properties of chiral drug candidates, remains a significant challenge in organic synthesis. Herein, a catalytic asymmetric strategy combining H/D exchange (H/D-Ex) and azomethine ylide-involved 1,3-dipolar cycloaddition (1,3-DC) was developed for the construction of biologically important enantioenriched α-deuterated pyrrolidine derivatives in good yields with excellent stereoselectivities and uniformly high levels of deuterium incorporation. Directly converting glycine-derived aldimine esters into the deuterated counterparts with D2O via Cu(i)-catalyzed H/D-Ex, and the subsequent thermodynamically/kinetically favored cleavage of the α-C–H bond rather than the α-C–D bond to generate the key N-metallated α-deuterated azomethine ylide species for the ensuing 1,3-DC are crucial to the success of α-deuterated chiral pyrrolidine synthesis. The current protocol exhibits remarkable features, such as readily available substrates, inexpensive and safe deuterium source, mild reaction conditions, and easy manipulation. Notably, the synthetic utility of a reversed 1,3-DC/[H/D-Ex] protocol has been demonstrated by catalytic asymmetric synthesis of deuterium-labelled MDM2 antagonist idasanutlin (RG7388) with high deuterium incorporation.

Electrochemically induced Markovnikov-type selective hydro/deuterophosphonylation of electron-rich alkenes.

The regioselective hydro/deuterophosphonylation of electron-rich alkenes with P(O)H compounds has been realized via a metal-free electrochemically induced strategy, accessing various Markovnikov-type adducts in high yields. A series of monodeuterated organophosphorus compounds with high deuterium (D) incorporation are subsequently obtained by adding D2O as the D source. The protocol features broad substrate scope, low energy consumption, high atom economy, and scalability. Monodeuterated organophosphoric acids can be synthesized via late-stage transformation.