Nano palladium catalyzed C(sp3)-H bonds arylation by a transient directing strategy

Reported herein is the first example of heterogeneous palladium catalyzed C(sp³)-H bonds arylation by a transient-ligand-directed strategy.Using supported palladium(metallic state) na nopariticles as catalyst,a wide range of aryl iodides undergo the coupling with various o-methylbenzaldehyde derivatives to assemble a library of highly selective and functionalized o-benzylbenzaldehydes.The stability of the catalyst was easily recovered four runs without significant loss of activity.The XPS analysis of the catalyst before and after reaction indicated that the reaction might be carried out by a catalytic cycle starting with Pd~0.     

Highly enantioselective amination of η3-(2-fluorocycloheptenyl)palladium complexes bearing chiral P,P- and P,N-ligands

The key enantioselectivity-determining step in Pd-catalyzed asymmetric amination of 2-fluoroallylic substrates was optimized using model reaction of η³-(2-fluorocycloheptenyl)-palladium complexes bearing chiral P,P- and P,N-ligands with various amines. (S)-ButPHOX was found to be the most effective ligand allowing the formation of 2-fluoroallyl amines and anilines with high enantioselectivity.     

Pyrene-tethered bismoviologens for visible light-induced C(sp3)–P and C(sp2)–P bonds formation

Developing efficient photosensitizers for C–P bond construction is highly important and remains a challenge due to the urgently needed for the synthesis of modified nucleosides, nucleotides, and other phosphine-containing ligands. Herein, two pyrene-tethered bismoviologen derivatives (Py-BiV²⁺) were designed and synthesized for visible-light-induced C–P bonds formation. The photochemical and electrochemical properties of Py-BiV²⁺ were studied systemically, certifying fine-tunable opto-electronic properties through the number of pyrene groups (4, n = 1; 6, n = 2). The prepared Py-BiV²⁺ showed strong light absorption, while retaining good redox features and chromic response features that were inherent to viologens. 4 exhibited accelerated photoinduced electron transfer in the presence of the electron donor (pyrene) and the generated 4′ (radical cation) showed higher stability. Accordingly, Py-BiV²⁺ directly served as photosensitizers for the first time in the visible-light-induced C(sp³)–P and C(sp²)–P bonds formation. As expected, these novel viologen derivatives exhibited good catalytic performance and good substrate expansibility under ambient conditions.     

Solvent-free and direct C(sp)–H amination of adamantanes by grinding

A facile, direct and environmentally benign conversion of C(sp³)–H bonds to C(sp³)–N bonds using substoichiometric amount of aprotic superelectrophiles polyhalomethane–AlX₃ has been achieved by grinding under solvent-free conditions at room temperature in air. It is a general and simple method for the direct amination of adamantanes, and a series of aminoadamantanes of azoles, arylamines or heteroarylamines were obtained in good to excellent yields. The advantages of this amination are atom economy, solvent-free, chemoselectivity, short reaction time and high yields.     

FeCl3 catalyzed sp C–H amination: synthesis of aminals with arylamines and amides

A simple and efficient amination of sp³ C–H bonds adjacent to a nitrogen atom in amides was introduced. The reaction was catalyzed by cheap and low toxic iron salt and used arylamines as nitrogen source. It provides a straightforward construction of acyclic aminals under mild conditions.     

Highly selective insertion of arynes into a C(sp)-O(sp3) σ bond

Arynes react with ethoxyacetylene to afford 2-ethoxyethynylaryl derivatives through a highly chemo- and regioselective formal insertion of the aryne into the C(sp)-O(sp(3)) bond of the alkyne. Computational studies suggest that the reaction does not proceed through a mechanism initiated by the nucleophilic addition of the oxygen atom to the aryne as previously proposed but by the addition of the triple bond of the alkyne to the aryne.     

TEMPO-Mediated Selective Synthesis of Isoxazolines, 5-Hydroxy-2-isoxazolines,and Isoxazoles via Aliphatic δ-C(sp3)-H Bond Oxidation of Oximes

Selective synthesis of three different bioactive heterocycles; isoxazolines, 5-hydroxy-2-isoxazolines and isoxazoles from the same starting material using TEMPO (2,2,6,6-Tetramethylpiperidin-1-oxyl) as a radical initiator is reported. Selectivity was achieved using different oxidants with TEMPO. The reaction goes through a 1,5-HAT (hydrogen atom transfer) process resulting in products with good yields. This strategy offers a straightforward route to three different heterocycles from oximes via radical-mediated C(sp³)-H oxidation.     

Highly efficient synthesis of polysubstituted 1,2-dihydroquinolines via tandem reaction of α-ketoesters and arylamines catalyzed by fluorous hydrazine-1,2-bis(carbothioate) and NCS

A simple and convenient tandem reaction of α-ketoesters with primary or secondary aromatic amines for the synthesis of polysubstituted 1,2-dihydroquinolines has been developed. The catalytic system (fluorous hydrazine-1,2-bis(carbothioate)/NCS) of the reaction has the advantages of operational simplicity, high efficiency, as well as easy recyclability.     

Metal-free sequential dual oxidative amination of C(sp3)–H bonds: A direct approach to benzothiadiazine 1,1-dioxide derivatives

An efficient and metal-free Di-tert-butyl peroxide (DTBP)-promoted dual oxidative amination annulation of 2-amino arylsulfonamide with methylarene has been developed. This protocol provides straightforward access to benzothiadiazine 1,1-dioxide derivatives without using prefunctionalized substrates in good to excellent yields with good functional group tolerance.     

Copper(II)-mediated intermolecular amination of inert C(sp3)H bonds with simple alkylamines to construct α,α-disubstituted β-amino acid derivatives

Disclosed herein is a copper(II)-mediated chelation-assisted intermolecular amination of inert C(sp³)H bonds using simple alkylamines as the amino source. A straightforward and step-economic alternative to α,α-disubstituted β-amino acid derivatives is provided consequently. This reaction features good functional group tolerance and relatively broad substrate scope. Furthermore, a coupling product between morpholine and radical inhibitor 2,6-di-tert-butyl-p-cresol (BHT) was isolated, indicating that a single electron transfer (SET) process might be involved in this transformation.     

Cobalt-catalyzed oxidative esterification of allylic/benzylic C(sp3)–H bonds

A protocol for the cobalt-catalyzed oxidative esterification of allylic/benzylic C(sp³)–H bonds with carboxylic acids was developed in this work. Mechanistic studies revealed that C(sp³)–H bond activation in the hydrocarbon was the turnover-limiting step and the in-situ formed [Co(III)]Ot-Bu did not engage in hydrogen atom abstraction (HAA) of a C–H bond. This protocol was successfully incorporated into a synthetic pathway to β-damascenone that avoided the use of NBS.     

Concise route to 3-arylisoquinoline skeleton by Lewis acid catalyzed C(sp3)-H bond functionalization and its application to formal synthesis of (±)-tetrahydropalmatine

An expeditious route to furnish an isoquinoline skeleton via hydride shift mediated C-H bond functionalization was developed. In this process, an unusual [1,5]-H shift without the assistance of the adjacent heteroatom took place to produce tetrahydroisoquinoline derivatives in good to excellent chemical yields. The formal synthesis of (±)-tetrahydropalmatine was achieved by exploiting this new transformation.     

Electrochemical NiH-Catalyzed C(sp3)−C(sp3) Coupling of Alkyl Halides and Alkyl Alkenes

Herein, an electrochemically driven NiH-catalyzed reductive coupling of alkyl halides and alkyl alkenes for the construction of Csp³−Csp³ bonds is firstly reported. Notably, alkyl halides serve dual function as coupling substrates and as hydrogen sources to generate NiH species under electrochemical conditions. The tunable nature of this reaction is realized by introducing an intramolecular coordinating group to the substrate, where the product can be easily adjusted to give the desired branched products. The method proceeds under mild conditions, exhibits a broad substrate scope, and affords moderate to excellent yields with over 70 examples, including late-stage modification of natural products and drug derivatives. Mechanistic insights offer evidence for an electrochemically driven coupling process. The sp³-carbon-halogen bonds can be activated through single electron transfer (SET) by the nickel catalyst in its low valence state, generated by cathodic reduction, and the generation of NiH species from alkyl halides is pivotal to this transformation.     

Direct Carbo-Acylation Reactions of 2-Arylpyridines with α-Diketones via Pd-Catalyzed C-H Activation and Selective C(sp2)-C(sp2) Cleavage

An efficient carbo-acylation reaction of 2-arylpyridines with α-diketones via Pd-catalyzed C-H bond activation and C-C bond cleavage in the presence of TBHP was developed that generated aryl ketones in good yields. The highly selective formation of aryl ketones was observed when 2-arylpyridines reacted with aromatic/aliphatic α-diketones.     

Isolation of chloro-bridged arylpalladium complexes, [Pd2Ar2(μ-Cl)2(PR3)2], in palladium catalyzed C–C cross coupling reaction of triarylbismuth with arylhalides

The reaction of [Pd₂Cl₂(μ-Cl)₂(PR₃)₂] with triarylbismuth in dichloromethane at room temperature afforded chloro-bridged arylpalladium complexes, [Pd₂Ar₂(μ-Cl)₂(PR₃)₂] (Ar = Ph or 4-MeC₆H₄ (tol)) in 85–90% yield as a yellow crystalline powder. These complexes were characterized by elemental analysis and NMR spectroscopy. Molecular structures of [Pd₂tol₂(μ-Cl)₂(PEt₃)₂] and [Pd₂Ph₂(μ-Cl)₂(PMePh₂)₂] were established by single crystal X-ray crystallography. These complexes are centrosymmetric dimers with trans configuration. The C–C coupling reaction between triarylbismuth and an arylhalide in the presence of a base is catalyzed by [Pd₂Cl₂(μ-Cl)₂(PR₃)₂]. The reactions proceed via an arylpalladium complex formed by transmetallation reaction between [Pd₂Cl₂(μ-Cl)₂(PR₃)₂] and Ar₃Bi. Probable reaction routes for C–C coupling have been discussed.     

Clustering of nonvalently bonded NO2…O2N fragments at C(sp3) atoms

Russian Chemical Bulletin - Based on the "invariom" approach and the "Atoms in Molecules" theory, a simplified method is proposed to reveal and analyze bonding interatomic...     

BF3·Et2O catalyzed intramolecular cyclization of diethyl 2-(dialkoxyphosphorylethynyl)-2-arylaminomalonates to 3-phosphonylated indoles

The boron trifluoride diethyl etherate catalyzed intramolecular cyclization of diethyl 2-(dialkoxyphosphorylethynyl)-2-arylaminomalonates afforded a series of novel 3-phosphonylated indoles, diethyl 2-[3-(dialkoxyphosphoryl)-1H-indol-2-yl]propanedioates. Decarboxylation of the latter compounds resulted in the formation of ethyl 2-[3-(dialkoxyphosphoryl)-1H-indol-2-yl]acetates.     

Direct Synthesis of Disubstituted 3-Isoquinolinone Derivatives through the Construction of C−N,C=O,and C(sp2)−C(sp3) Bonds under Transition-Metal-Free Conditions

The efficient three-component cascade coupling reaction of 3-haloisoquinolines, haloalkanes, and sp³-carbon nucleophiles (acetophenone or nitromethane) led to a series of structurally novel 1,2-disubstituted-3-isoquinolinones through the formation of C(sp³)−C(sp²), C−N, and C=O bonds. The NaOAc-promoted reaction described in this work is simple to operate, environment friendly, and highly selective.