Arylation Of Benzene Research Articles

C–H Arylation of Benzene with Aryl Halides using H2 and a Water‐Soluble Rh‐Based Electron Storage Catalyst

This paper reports the first example of C-H arylation of benzene under mild conditions, using H2 as an electron source {turnover numbers (TONs)=0.7-2.0 for 24 h}. The reaction depends on a Rh-based electron storage catalyst, and proceeds at room temperature and in aqueous solution. Furthermore, the H2 is inactive during the radical transfer step, greatly reducing unwanted side reactions.

Mechanism of the t-BuOM (M = K, Na, Li)/DMEDA-Mediated Direct C–H Arylation of Benzene: A Computational Study

Over the past ten years, a combination of organic additive and t-BuOK/t-BuONa has been successfully used for the direct C–H arylation of arenes. Conceptually different from transition-metal-catalyzed cross-coupling reactions, these t-BuOK-mediated reactions have raised significant curiosity among organic chemists. Herein, a systematic computational study of each elementary step of the t-BuOM (M = K, Na, Li)/N 1,N 2-dimethylethane-1,2-diamine (DMEDA) mediated direct C–H arylation of benzene is detailed. The presented mechanistic proposal relies on the complexation and reaction of t-BuOM with DMEDA (additive), which leads to the formation of different complexes such as SED(M+)…PhI. These complexes mainly involve coordination of the metal ion (from t-BuOM) to the additive and iodobenzene via stabilizing cation–lone pair and cation–π interactions. Such complexation of a metal ion to an additive and iodobenzene not only ensures facile electron transfer to iodobenzene but also provides a lowest energy pathway for the subsequent radical addition and deprotonation step.

Alumina as Solid‐State Ligand in Enhancing the Redox Catalytic Property of Iron Oxide Grafted AlSBA‐15 towards Arylation of Arene

Abstract2–8 wt % iron has been grafted over SBA‐15 and 10 wt % alumina grafted SBA‐15 (AlSBA‐15) through selective extraction deposition technique using LaFeO3 as iron precursor in acidic solution. DRS‐UV spectra confirmed the presence of iron as isolated Fe(III), Fe(III)‐clusters and amorphous FeOx oligomers. SEM‐EDX mapping, FT‐IR, XPS, HR‐TEM and 27Al MAS NMR characterisation results confirmed that iron grafted over AlSBA‐15 preferentially reside on the alumina. The donor‐acceptor interaction of grafted iron ions with alumina atoms displaying Lewis acid properties stabilized iron at higher oxidation state Fe(III+δ). This increased the BE of Fe2p electrons (XPS) and shifted the temperature of iron reduction in 2–8 wt %Fe/AlSBA‐15 materials to higher value (600 °C) compared with Fe/SBA‐15 (H2‐TPR). In arylation of benzene, 8 wt %Fe/AlSBA‐15 demonstrated excellent redox catalytic activity with TOF close to homogeneous catalyst and 82 % biphenyl yield. The catalyst demonstrated consistent catalytic performance for 7 cycles.

A Sustainable Heterogeneous Iron Catalyst Fe/SBA‐15 towards Direct Arylation of Unactivated C(sp3)−H and C(sp2)−H Bonds with Arenes

AbstractIron grafted over mesoporous silica (8 wt %Fe/SBA‐15) is a sustainable, efficient heterogeneous iron catalyst for direct arylation of biphenyl methane C(sp3)−H and benzene C(sp2)−H bonds. The selective extraction deposition (SED) technique was adopted to graft iron easily over the mesoporous support SBA‐15 by using LaFeO3 as an iron precursor. The synthesized catalyst has been characterized by EPR spectroscopy, diffuse reflectance UV/Vis spectroscopy, and temperature programmed reduction (TPR) analysis to understand the coordination environment and state of oxidic iron species grafted over the mesoporous SBA‐15. TPR results confirm the presence of isolated, clustered, oligomeric oxidic iron species in the catalyst. The adopted SED technique is highly successful for grafting 8 wt % iron into the mesopores of SBA‐15 without forming iron oxide particles. Unlike homogeneous iron, the 8 wt %Fe/SBA‐15 catalyst does not need support from an electron‐withdrawing group and additives to carry out arylation of benzene and could be successfully recycled five times.

Polyureas derived from CO2 and diamines: highly efficient catalysts for C–H arylation of benzene

Heterogeneous polyureas were effective for C–H arylation of benzene in the presence of t-BuOK, producing biaryl products in high yields up to 97%.

N-Doped porous carbon nanotubes: synthesis and application in catalysis.

Uniform N-doped carbon nanotubes were obtained for the first time via a morphology-preserving thermal transformation of organic polymer nanotubes without any additional templates. These carbon nanotubes acted as a superior metal-free carbon catalyst for C-H arylation of benzene, reductive hydrogen atom transfer and oxidation reactions.

Ferrocene catalysed C–H arylation of arenes and reaction mechanism study using cyclic voltammetry

Ferrocene catalysed C–H arylation of benzene using aryldiazonium salt is studied. Yield of biphenyl in this reaction was found to be better than some of the known methods. Aryldiazonium salts with electron withdrawing groups produced excellent yields (upto 85%) in C–H arylation. Applicability of this reaction was studied on several arenes and heteroarene such as benzene, naphthalene, anthracene, pyrene and pyridine. Catalytic role of ferrocene in aryl radical formation was studied by cyclic voltammetry of phenyldiazonium tetrafluoroborate. In presence of ferrocene more radical formation was observed. This reaction model works at ambient temperature and features the use of inexpensive catalyst for the synthesis of biaryl derivatives.

Graphene Oxide Promoted C–H Arylation of Benzene with Aryl Halides

Graphene Oxide Promoted C–H Arylation of Benzene with Aryl Halides

Mechanistic Insights into the Initiation Step of the Base Promoted Direct C-H Arylation of Benzene in the Presence of Additive.

The direct arylation of unactivated arenes is a very practical and highly convenient procedure for the construction of biaryl scaffolds. Recently, a direct arylation of unactivated benzene has been achieved in the presence of base (tBuOK or tBuONa) and organic additive such as 1,10-phenanthroline. However, details of intimate mechanism of reaction as well as the role of additive have remained elusive until date. The present work explores various mechanistic possibilities of the key electron transfer step of the reaction in order to identify a probable route for the initiation of phenyl radical from iodobenzene. A detailed DFT (M06-2X functional) investigation indicates that the reaction of additive and base can be crucial to generate an electron acceptor-donor pair that can facilitate electron transfer mechanism. This computational model provides a satisfactory explanation for experimental observations, clearly defining the roles of additive and base in the reaction.

ChemInform Abstract: Ligand‐Controlled Chemoselectivity in Potassium tert‐Amylate‐Promoted Direct C—H Arylation of Unactivated Benzene with Aryl Halides.

AbstractPotassium tert‐amylate promotes the direct C—H arylation of benzene in the presence of small ligands like dimethylethylenediamine or phen, providing an efficient, transition‐metal‐free radical cross‐coupling protocol for preparation of biaryls.

C60-catalyzed direct C–H arylation of benzene with aryl iodides in air

C60 at 1 mol % loading catalyzed the direct C–H arylation of benzene with aryl iodides in air to yield biaryls. The in situ generation of electron-rich C60(OH)2−, from C60 and OH−, reduced the aryl iodides to aryl radicals for arylation of benzene. The large surface area and spherical shape of C60 facilitated this process.

Triphyrin catalyzed direct C–H arylation of benzene with aryl halides

Transition-metal free direct C–H arylation of benzene with aryl halides was achieved by meso-aryl-substituted [14]triphyrins(2.1.1) catalysts in an air atmosphere. Various aryl halides underwent successful direct C–H arylation of benzene to give moderate to high yields of biaryls. A radical mechanism is proposed for this triphyrin catalyzed C–H arylation reaction.

Room-Temperature Photoinduced Direct C–H-Arylation via Base-Promoted Homolytic Aromatic Substitution

Conceptually different approach toward biaryl syntheses by photoinduced direct C-H arylation of benzene and thiophene in the presence of t-BuOK is reported. The reaction proceeds through photo- and base-promoted homolytic aromatic substitution. The o-, m- and p- substituted ArI, as well as the electron-donating and electron-withdrawing nature of the substituents were found be good to excellent substrates. Heteroaryl, ArBr, ArCl and double C-H arylation were successfully achieved.

ChemInform Abstract: Metal‐Free Arylation of Benzene and Pyridine Promoted by Amino‐Linked Nitrogen Heterocyclic Carbenes.

AbstractAn amino‐linked nitrogen heterocyclic carbene mediates the carbon—carbon coupling reaction through direct C—H functionalization of benzene (II) and pyridine (IV) with aryl iodides (I) in the absence of a metal catalyst.

Free porphyrin catalyzed direct C–H arylation of benzene with aryl halides

A general procedure for free porphyrin catalyzed direct C–H arylation of benzene was demonstrated. This air tolerant, transition-metal-free process provides a promising system for cheap and efficient synthesis of biaryls in a user-friendly approach.

Electronic Effects of Ligands on the Cobalt(II)–Porphyrin‐Catalyzed Direct C–H Arylation of Benzene

AbstractThe electronic effects of the porphyrin ligand on the cobalt(II)‐porphyrin‐catalyzed direct C–H arylation of benzene with 4‐iodotoluene were explored. The investigation was facilitated by the easy preparation of various substituted porphyrin ligands. The reaction rates were found to be dependent on the electron richness of the cobalt(II)–porphyrins. Such effects are consistent with the electronic influences on the rate‐determining aryl iodide bond cleavage.

ChemInform Abstract: tert‐Butoxide‐Mediated Arylation of Benzene with Aryl Halides in the Presence of a Catalytic 1,10‐Phenanthroline Derivative.

AbstractCross coupling of aryl halides (II), (V), (IX) with unactivated arenes (I) and (IV) proceeds smoothly in the system NaOtBu—diphenylphenanthroline without the use of transition metal catalysts.

Direct C-H Arylation of Benzene, Naphthalene, and Pyridine

Direct C-H Arylation of Benzene, Naphthalene, and Pyridine

Cp2Ni-KOt-Bu-BEt3 (or PPh3) Catalyst System for Direct C−H Arylation of Benzene, Naphthalene, and Pyridine

Ni-catalyzed direct C-H arylation of benzene and naphthalene using aryl halides was investigated. For the first time, the arylation was successfully catalyzed by Cp(2)Ni (5 mol %) in the presence of KOt-Bu and BEt(3). This Ni catalyst system was also applied to direct C-H arylation of pyridine, an electron-deficient heteroarene; PPh(3) was used instead of BEt(3) in this case.

Rapid Assembly of Tetrahydrodibenzofurans and Tetrahydrocarbazoles from Benzene and o‐Iodophenols and o‐Iodoanilines: Reductive Radical Arylation of Benzene in Action.

Abstract In the presence of catalytic benzeneselenol, generated in situ from diphenyl diselenide, tributyltin hydride brings about the radical addition of ortho-functionalized aryl iodides to benzene giving aryl cyclohexadienes. These may then be cyclized by means of standard electrophilic reagents. The use of o-methoxycarbamoyliodobenzene leads to a tetrahydrocarbazole, whereas o-iodobenzoic acid provides a tetrahydrodibenzopyranone. o-Iodophenols lead, overall, to tetrahydrodibenzofurans.