Cross-dehydrogenative Coupling Research Articles

Silver(I)-catalyzed highly para-selective phosphonation of 2-aryloxazolines.

A silver-catalyzed phosphonation of 2-aryloxazolines has been accomplished. This protocol provides highly regioselective access to para-phosphonation products with good functional group tolerance and moderate to good yields via cross-dehydrogenation coupling. Mechanistic studies have shown that para-phosphonation products are obtained via a radical pathway. Furthermore, the directing oxazoline group in the para-phosphonation products is removable and can be converted to benzoic esters.

Photocatalytic dehydrogenative C(sp2)–P coupling reaction between dibenzo[b,f][1,4]oxazepanes and phosphine oxides

Visible-light-induced cross-dehydrogenative coupling between cyclic imines and diaryl phosphine oxides has been developed to afford their oxyphosphide derivatives, using rhodamine B as a photocatalyst.

Preparation of an OHCP nanofiber photocatalyst for cross-dehydrogenation coupling reactions

Phloxine B (PHB) exhibited high catalytic efficiency in cross-dehydrogenation coupling (CDC) reactions.

Iodine-enabled organoelectrocatalysis: enantioselective cross dehydrogenative coupling of sulfides and aldehydes

A method for the direct asymmetric α-sulfenylation of aldehydes with sulfides was developed.

Hollow anatase TiO2 tetrakaidecahedral crystals with an active {001}/{110} redox interface toward high-performance photocatalytic activity.

The existence of the oxidation/reduction interface can promote the performance of a photocatalyst, due to its effect on the separation of photogenerated carriers and the surface reactivity. However, it is difficult to construct two sets of oxidation/reduction interfaces in a single crystal and compare their separation efficiency for photogenerated carriers. Introducing a high proportion of active facets into the co-exposed facets is even more challenging. Herein, a hollow anatase TiO2 tetrakaidecahedron (HTT) with two sets of oxidation/reduction interfaces ({001}/{101} and {001}/{110}) is synthesized by directional chemical etching. Theoretical and experimental results indicate that the {001}/{110} interface is a dominant oxidation/reduction interface, showing a better promotion on the separation of photogenerated carriers than the {001}/{101} interface. In the HTT, the ratio of dominant {001}/(110) is increased and the proportion of the active {110} facet is about 40% (generally about 15%). Therefore, the HTT shows excellent catalytic activity for photocatalytic reductive (hydrogen production) and oxidative (selective oxidation of sulfides) reactions. The HTT also demonstrates favorable photocatalytic activity for the cross-dehydrogenative coupling reaction, where both photogenerated electrons and photogenerated holes are involved, further verifying its high separation efficiency of photogenerated carriers and surface reactivity. This work provides an important guideline for developing advanced structures with a predetermined interface toward desired applications.

Transition-metal-free access to benzyl ethers via aerobic cross-dehydrogenative coupling of benzylic C(sp3)–H bonds with alcohols

We have developed an efficient and green cross-coupling reaction for alkoxylation of the primary benzylic C(sp3)–H bond. KOtBu was used as a catalyst and O2 was used as the sole oxidant in the methoxylation of the primary benzylic C–H bond.

Metal-free visible light-induced cross-dehydrogenative coupling of benzocyclic imines with water/P(O)H compounds: efficient access to functionalized benzazepines/ones

A metal-free visible light-induced cross-dehydrogenative coupling of aldimines with nucleophiles in a one-pot fashion is first reported, which features high efficiency,the absence of external oxidants, and mild and redox-neutral reaction conditions.

Metal- and photosensitizer-free cross-dehydrogenative coupling through photoinduced energy transfer

This study introduces a novel, eco-friendly method for Minisci alkylation without harmful catalysts, advancing sustainable pharmaceutical synthesis through energy transfer from heteroarenes to peroxide, offering significant environmental benefits.

FeBr3-catalysed synthesis of 3-aroylimidazo[1,2-a]pyridine and 3,3'-(arylmethylene)bis(2-phenylimidazo[1,2-a]pyridines) derivatives from 2-arylimidazo[1,2-a]pyridines and aromatic aldehydes: an investigation about mechanistic insights.

In a new approach, a series of 3-aroylimidazo[1,2-a]pyridine derivatives were prepared in high yields. This approach revealed the direct Fe-catalyzed functionalization of imidazo[1,2-a]pyridine derivatives with aryl aldehydes via an aerobic oxidative cross-dehydrogenative coupling process. This transformation occurred in the presence of air, and FeBr3 served as a homogeneous Lewis catalyst. O2 was found to be the principal oxidant responsible for the method's success. Interestingly, when these reactions were carried out under an argon atmosphere, 3,3'-(arylmethylene)bis(2-phenylimidazo[1,2-a]pyridines) derivatives were prepared in good yields.

Palladium-catalyzed cross-dehydrogenative coupling of (hetero)arenes

A general and authoritative literature overview on Pd-catalyzed cross-dehydrogenative coupling reactions of (hetero)arenes from the origins to 2023, where not only the synthetic aspects were described but also the most relevant mechanistic features.

Correction: Ethanol-assisted mechanochemical asymmetric cross-dehydrogenative coupling reaction with recoverable chiral amine/NaCl for accessing chiral α-alkyl α-glycine derivatives

Correction for ‘Ethanol-assisted mechanochemical asymmetric cross-dehydrogenative coupling reaction with recoverable chiral amine/NaCl for accessing chiral α-alkyl α-glycine derivatives’ by Jingbo Yu et al., Green Chem., 2024, https://doi.org/10.1039/d4gc00947a.

Enantioselective cross-dehydrogenative coupling enabled by organocatalysis

Organocatalytic enantioselective cross-dehydrogenative coupling reaction provides a great opportunity for the synthesis of highly enantioenriched molecules. In this review, recent progress in this field is summarized.

Asymmetric 1,2-diaxial synthesis of bi-(hetero)aryl benzofulvene atropisomers via transient directing group-assisted dehydrogenative coupling.

The efficient cross-dehydrogenative coupling of electronically rich and sterically congested benzofulvene with bi-(hetero)aryl moieties to construct an axially chiral benzofulvene core remains a formidable task. In this study, we describe a highly efficient and practical palladium-catalyzed approach for atroposelective bi-(hetero)aryl benzofulvene synthesis, achieving excellent enantioselectivity with moderate yields. This protocol offers a remarkable opportunity for the direct regio- and enantioselective conversion of C-H bonds of benzofulvene to C-C bonds. Furthermore, the protocol permits the incorporation of benzofulvene with a 4-phenyl coumarin core, enabling access to a novel class of axially chiral coumarins.

Ethanol-assisted mechanochemical asymmetric cross-dehydrogenative coupling reaction with recoverable chiral amine/NaCl for accessing chiral α-alkyl α-glycine derivatives

Ethanol-assisted grinding effectively facilitated aerobic asymmetric cross-dehydrogenative coupling of glycine esters/amides with ketones/aldehydes, deploying reusable chiral amine/NaCl for rapid synthesis of chiral α-alkyl α-glycine derivatives.

Photoinduced decarboxylative germylation of α-fluoroacrylic acids: access to germylated monofluoroalkenes.

Herein, a novel strategy is presented for the photoinduced decarboxylative and dehydrogenative cross-coupling of a wide range of α-fluoroacrylic acids with hydrogermanes. This methodology provides an efficient and robust approach for producing various germylated monofluoroalkenes with excellent stereoselectivity within a brief photoirradiation period. The feasibility of this reaction has been demonstrated through gram-scale reaction, conversion of germylated monofluoroalkenes, and modification of complex organic molecules.

Rationally designed C-3 sulfenylated 2-phenyl-4H-pyrido[1,2-a]pyrimidin-4-one based fluorescent probe for recognition of Fe3+

Cross-dehydrogenative coupling (CDC) efficiently constructs complex organic molecules by directly coupling two C-H bonds from different substrates. This enables the functionalisation of existing chromophores with different substituents, facilitating efficient sensor development. Electronically diverse C-3 sulfenylated 2-phenyl-4H-pyrido[1,2-a]pyrimidin-4-ones (3a-3d) were synthesised using iodine mediated CDC protocol and structurally characterised using FT-IR, 1H and 13C NMR and mass spectrometry technique. Single crystal X-ray diffraction technique was utilised for establishing the molecular structure of 3d. The absorption and emission intensity for all the synthetics were recorded in the range of 365-375 and 406-509 nm, respectively in solvents of varying polarity. Compound 3b, with distinct dispersion of the frontier molecular orbitals due to ring extension, showed exceptional absorption and emission intensity in water and methanol. All the sensing applications of 3b were investigated using water/methanol (1:4; v/v) as the solvent system. An abrupt increase in the absorption intensity with a decrease in emission maxima of 3b was observed upon Fe(NO3)3.9H2O addition. A detection limit of 1.27 × 10−6 M, low response time and thermal stability served as some of the characteristic features which established the probe as a potential sensor for Fe3+ ion. Further, the stoichiometry and binding constant of the complex was determined by Benesi-Hildebrand and Job's plot.

Flavin‐Catalyzed Aerobic Oxidative C−C Bond Formation by Metal/Light‐Free Cross‐Dehydrogenative Coupling

AbstractBiomimetic flavin catalysts enable green and selective aerobic oxidative transformations. However, most previous studies tended to focus on reproducing the enzymatic function of flavin monooxygenase, thereby limiting the applications of flavin catalysts to oxygen‐atom transfer reactions. We herein report a cross‐dehydrogenative coupling (CDC) between the sp3 C−H bond of tetrahydroisoquinolines and the sp3 and sp2 C−H bonds of carbon nucleophiles, such as α‐methylene carbonyl compounds, nitromethane, and indoles, for C−C bond formation promoted by flavin catalysts. Flavin catalysis enables the oxidative C−H activation of tetrahydroisoquinolines and the efficient activation of molecular oxygen (1 atm) under mild and metal/light‐free conditions, thus facilitating a green aerobic CDC that generates benign water as the sole by‐product.

Low-Valent-Tungsten-Catalyzed Aerobic Oxidative Cross-Dehydrogenative Coupling Reaction.

A straightforward and convenient protocol was established for the synthesis of thiophosphates and 3-sulfenylated indoles via low-valent-tungsten-catalyzed aerobic oxidative cross-dehydrogenative coupling reactions. These reactions occur under mild conditions and simple operations with commercially available starting materials, processing the advantage of excellent atom and step economy, broad substrate scope, and good functional groups tolerance. Moreover, this transformation could be practiced on the gram scale, which exhibits great potential in the preparation of drug-derived or bioactive molecules.

Iodine-Catalyzed Radical C-H Amination of Nonaromatic Imidazole Oxides: Access to Cyclic α-Aminonitrones.

A straightforward cross-dehydrogenative coupling approach to incorporate alicyclic amino residues into the structure of model cyclic aldonitrones, 2H-imidazole oxides, is reported. The elaborated C(sp2)-H functionalization is achieved by employing cyclic amines in the presence of the I2-tert-butyl hydroperoxide (TBHP) reagent system. As a result, a series of 19 novel heterocyclic derivatives were obtained in yields of up to 97%. A mechanistic study involving electron paramagnetic resonance spectroscopic experiments allowed the radical nature of the reaction to be confirmed. In particular, the envisioned mechanistic rationale comprises N-iodination of a cyclic amine, followed by N-I bond homolysis of the resulting intermediate and subsequent amination of the nitrone moiety via the newly generated nitrogen-centered radical.

Chemical Synthesis of Substituted Naphthalene Derivatives: A Review

AbstractThis review outlines progress in the synthesis of substituted naphthalene derivatives. Naphthalene and its derivatives exhibit various biological activities such as anti-inflammatory, anticancer, antiviral, antitubercular, antimicrobial, antihypertensive, antidiabetic, etc. Several strategies have been developed for the construction of naphthalene derivatives, primarily focused on metal-catalyzed reactions (palladium, copper, zinc, rhodium, platinum, nickel, etc.,) and Lewis acid catalyzed transformations. This review discusses the preparations of naphthalene derivatives using various salts such as gallium chlorides, gold chlorides, gold bromides, various gold complexes as well as Brønsted acids like triflic acid and trifluoroacetic acid, and Lewis acids such as boron trifluoride etherate. Additionally, miscellaneous types of reactions are explored involving both metal and Lewis acids. The transformational approaches covered in this review include cycloadditions, carboannulations, benzannulations, electroannulations, rearrangements, and cross-dehydrogenative coupling reactions. Overall this review provides a comprehensive and up-to-date account of the current state of preparations of substituted naphthalenes, highlighting their medicinal and industrial importance.1 Introduction1.1 Medicinal Importance of Naphthalenes2 Synthesis of Substituted Naphthalenes2.1 Metal-Catalyzed Reactions2.1.1 Palladium-Catalyzed Reactions2.1.2 Copper-Catalyzed Reactions2.1.3 Zinc-Catalyzed Reactions2.1.4 Iron-Catalyzed Reactions2.1.5 Rhodium-Catalyzed Reactions2.1.6 Platinum-Catalyzed Reactions2.1.7 Nickel-Catalyzed Reactions2.1.8 Other Metal-Catalyzed Reactions3 Lewis Acid Catalyzed Reactions4 Miscellaneous Reactions5 Conclusion