Diaryl Ketones Research Articles

Autocatalytic Friedel‐Crafts Acylation of Arenes without Additional Catalyst and Additive

AbstractA new and autocatalytic method was developed for Friedel‐Crafts acylation of arenes without additional catalyst and additive. A series of electron‐rich arenes underwent the acylation to give the targeted product in low to high yields by using aryl, alkyl and vinyl acyl chlorides as the acylating reagent, which gave an effective method for the preparation of diaryl ketones, alkyl aryl ketones and α,β‐unsaturated ketones. Preliminary mechanistic investigation suggested that the present acylation displayed an induction period and a sigmoid kinetic profile characteristic of autocatalytic systems, and the resulting H+ played a role of the catalyst.

Palladium nanoparticles on amino-modified silica-catalyzed C–C bond formation with carbonyl insertion

A practical and heterogeneously catalyzed Stille, homo-coupling, and Suzuki carbonylation reaction has been reported using Pd nanoparticles supported on amino-vinyl silica-functionalized magnetic carbon nanotube (CNT@Fe3O4@SiO2-Pd) for the efficient synthesis of symmetrical and unsymmetrical diaryl ketones from aryl iodides. A wide variety of symmetrical and unsymmetrical diaryl ketones were obtained in high yields under CO gas-free conditions using Mo(CO)6 as an efficient carbonyl source. Considering the atom economy of Ph3SnCl, less than an equimolar amount can be applied in Stille transformation, which is of great importance due to the toxicity of organotin derivatives. Moreover, no phosphine ligand and external reducing agent were necessary in these coupling carbonylation reactions. This heterogeneous Pd catalyst offers high activity with very low palladium leaching. Finally, the catalyst can be reused and recycled for six steps without loss in activity, exhibiting good example of sustainable methodology.

A convenient pinacol coupling of diaryl ketones with B2pin2via pyridine catalysis.

A convenient, pyridine-boryl radical-mediated pinacol coupling of diaryl ketones is developed. In contrast to the conventional pinacol coupling that requires sensitive reducing metal, the current method employs a stable diboron reagent and pyridine Lewis base catalyst for the generation of a ketyl radical. The newly developed process is operationally simple, and the desired diols are produced with excellent efficiency in up to 99% yield within 1 hour. The superior reactivity of diaryl ketone was observed over monoaryl carbonyl compounds and analyzed by DFT calculations, which suggests the necessity of both aromatic rings for the maximum stabilization of the transition states.

Palladium imine-pyridine-imine complex immobilized on graphene oxide as a recyclable catalyst for the carbonylative homo-coupling of aryl halides

A heterogeneous 3-N,N,N-(II) Pd(OAc)2 catalyst was prepared from the reaction of Pd(OAc)2 with Si-Prn-N = C-Py-C = N-Prn-Si immobilized on graphene oxide (GO-Si-Prn-N = C-Py-C = N-Prn-Si-GO). The prepared catalyst was characterized by inductively coupled plasma optical emission spectroscopy, Fourier transform infrared (FT-IR) spectroscopy, Raman spectroscopy, energy dispersive X-ray spectroscopy, X-ray diffraction, UV-vis spectroscopy, BET surface area, scanning electron microscopy, transmission electron microscopy, and thermogravimetric analysis. The catalyst was employed as a heterogeneous catalyst for carbonylative homo-coupling of aryl iodides and bromides under carbon monoxide gas-free condition. Cr(CO)6 was used as the carbon monoxide source and the desired symmetrical diaryl ketones were achieved in good to excellent yields. Moreover, the catalyst was reused up to five consecutive cycles without significant loss of activity.

Microwave assisted, BF3.OEt2 catalyzed efficient synthesis of tosylhydrazones and SC-XRD study of two of the synthesized tosylhydrazones

A highly efficient methodology for transformation of carbonyl compounds to their corresponding tosylhydrazones under microwave irradiation in presence of BF 3 .OEt 2 catalyst has been developed and described here. The methodology is highly prospective for tosylhydrazone synthesis especially of diaryl ketones, as already existing procedures are found to be less effective for the same. Seventeen carbonyl compounds have been studied and found to deliver their corresponding products in excellent yield (92-98%). The products crystallize out from the reaction mixture during cooling at room temperature which excludes further purification processes. Single crystal X-ray diffraction (SC-XRD) analysis of two of the synthesized tosylhydrazones have been carried out and reported here.

Pd‐Catalyzed Decarboxylative Ortho‐Aroylation of 2‐Aryl‐quinazolinone Comprising Intrinsic Directing Group with α‐Oxocarboxylic Acids

AbstractPd‐catalyzed decarboxylative ortho‐aroylation of 2‐aryl‐quinazolinones with α‐oxocarboxylic acids for the synthesis of diaryl ketones has been developed. Biologically interested novel quinazolinones with diaryl ketone functionality has been obtained with moderate to excellent yield from easily accessible 2‐aryl‐quinazolinones having inherent directing group.

Chiral Electron-Rich PNP Ligand with a Phospholane Motif: Structural Features and Application in Asymmetric Hydrogenation.

Despite the remarkable reactivity that was achieved by a series of transition-metal catalysts with a PNP type ligand, the electron-rich chiral PNP ligands have still been rarely reported because of the difficulties in synthesis and the nature of air-sensitivity. Herein, we report a novel chiral PNP ligand (Heng-PNP) with both a rigid backbone and a bulky tert-butyl group on the phospholane motif. We successfully obtained its divalent iron complex. The chiral environment of its Ir(III) complex was also discussed with quadrant analysis. This tridentate ligand was applied in iridium-catalyzed asymmetric hydrogenation of challenging diaryl ketones: up to 98% ee and 500 TON are achieved. Computational study showed that the twist of conjugate aryl group in the substrate (induced by the special chiral pocket of Ir/Heng-PNP complex) leads to the energy difference in the enantiodetermining step.

Visible Light-Enabled sp3 -C-H Functionalization with Chloro- and Bromoalkynes: Chemoselective Route to Vinylchlorides or Alkynes.

An unprecedented direct atom‐economic chemo‐ and regioselective hydroalkylation of chloroalkynes and an sp3‐C−H alkynylation of bromoalkynes was achieved. The reaction partners are unfunctionalized ethers, alcohols, amides, and even non‐activated hydrocarbons. We found that a household fluorescent bulb was able to excite a diaryl ketone, which then selectively abstracts a H‐atom from an sp3‐C−H bond. The product of a formal alkyne insertion into the sp3‐C−H bond was obtained with chloroalkynes, providing valuable vinyl chlorides. The photo‐organocatalytic hydrogen atom transfer strategy gives rise to a broad range of diversely functionalized olefins. When bromoalkynes are applied in the presence of a base, a chemoselectivity switch to an alkynylation is observed. This reaction can even be performed for the alkynylation of unactivated sp3‐C−H bonds, in this case with a preference of the more substituted carbon. Accompanying quantum chemical calculations indicate a vinyl radical intermediate with pronounced linear coordination of the carbon radical center, thus enabling the formation of both diastereoisomers after H‐atom abstraction, suggesting that the (Z)‐diastereoisomer is preferred, which supports the experimentally observed (E/Z)‐distribution.

Asymmetric Transfer Hydrogenation of Densely Functionalized Diheteroaryl and Diaryl Ketones by a Ru-Catalyst of Minimal Stereogenicity

A highly enantioselective asymmetric transfer hydrogenation (ATH) of densely functionalized diheteroaryl and diaryl ketones was developed using Ru-catalysts of minimal stereogenicity. Various ketone substrates with structurally and electronically similar groups attached to the prochiral centers were reduced successfully in good to excellent enantioselectivities and yields. This protocol provides practical and efficient access to chiral diheteroarylmethanols and benzhydrols, which are key intermediates in pharmaceuticals and biologically active compounds.

Regiodivergent Access to 2- or 3-Substituted Indanones: Catalyst-Controlled Carboacylation via C–C Bond Activation

Indanones are ubiquitous in biologically active compounds. Intramolecular hydroacylation of aldehydes and alkenes is an efficient and atom-economic route to indane rings. However, these reactions a...

Carbonylative Suzuki–Miyaura Coupling Reactions of Aryl Iodides with Readily Available Polymer-Immobilized Palladium Nanoparticles

Polysilane/alumina-supported palladium nanoparticle catalyzed carbonylative Suzuki–Miyaura coupling reactions under ligand-free conditions have been developed to synthesize diaryl ketones. High yields and selectivities were achieved even with low catalyst loading under atmospheric pressure of CO gas. A variety of aryl iodides and arylboronic acids could be utilized to afford the diaryl ketones in excellent yields. Moreover, the ligand-free immobilized palladium nanoparticles could be recovered by simple filtration and the catalytic activity could be maintained for several runs.

Decarboxylative Cross-Coupling of Acyl Fluorides with Potassium Perfluorobenzoates

We report the transition metal-free decarboxylative cross-coupling reactions of acyl fluorides with potassium perfluorobenzoates. Compared with traditional transition metal-catalyzed cross-couplings, this protocol presents an extremely environmentally benign pathway to afford unsymmetrical diaryl ketones. To install perfluorophenyl groups, this method highlights highly selective, inexpensive, and nontoxic conditions. The reaction system tolerates various functional groups in acyl fluorides. Remarkably, all of the starting materials can be prepared from abundant carboxylic acids and the reaction proceeds without any catalysts and additives.

Pd(II)-Catalyzed C-H Acylation of (Hetero)arenes—Recent Advances

Di(hetero)aryl ketones are important motifs present in natural products, pharmaceuticals or agrochemicals. In recent years, Pd(II)-catalyzed acylation of (hetero)arenes in the presence of an oxidant has emerged as a catalytic alternative to classical acylation methods, reducing the production of toxic metal waste. Different directing groups and acyl sources are being studied for this purpose, although further development is required to face mainly selectivity problems in order to be applied in the synthesis of more complex molecules. Selected recent developments and applications are covered in this review.

Palladium‐Catalyzed Suzuki Coupling of N‐Acyloxazolidinones via Selective Cleavage of C–N Bonds

By implementing a palladium‐catalyzed Suzuki coupling reaction of N‐acyloxazolidinones with arylboronic acid, we herein report on the preparation of substituted diaryl ketones via selective cleavage of exocyclic C–N Bonds. The reaction was carried out under mild reaction conditions with excellent functional group compatibility in good yields (up to 93 %).

Highly Enantioselective Cobalt-Catalyzed Hydroboration of Diaryl Ketones.

A highly enantioselective cobalt-catalyzed hydroboration of diaryl ketones with pinacolborane was developed using chiral imidazole iminopyridine as a ligand to access chiral benzhydrols in good to excellent yields and ee. This protocol could be carried out in a gram scale under mild reaction conditions with good functional group tolerance. Chiral biologically active 3-substituted phthalide and (S)-neobenodine could be easily constructed through asymmetric hydroboration as a key step.

Ruthenium-Catalyzed Carbonylative Coupling of Anilines with Organoboranes by the Cleavage of Neutral Aryl C–N Bond

Herein, we report the first ruthenium-catalyzed Suzuki-type carbonylative reaction of electronically neutral anilines via C(aryl)-N bond cleavage. Without any ligand and base, diaryl ketones can be obtained in moderate to high yields by using Ru3(CO)12 as the catalyst and chelation assisted by pyridine. The pyridine ring has a significant effect on both high efficiency and high regioselectivity in the cleavage of the aryl C-N bond in anilines.

Carbonyl-Stabilized Phosphorus Ylide as an Organocatalyst for Cyanosilylation Reactions Using TMSCN

We report carbonyl-stabilized phosphorus ylides as general and efficient catalysts for the cyanosilylation of ketones. The N,N-diethylacetamide derived phosphorane is identified as an extremely efficient catalyst for the cyanosilylation of dialkyl ketones, alkyl aryl ketones, diaryl ketones, and α,β-unsaturated enones with catalyst loading down to 0.005 mol %, the lowest ever known for ketone cyanosilylation. Aldehydes, aldimines, and ketimines are also viable substrates. By NMR and React IR analysis, as well as electrical conductivity experiments, it is proposed that the phosphorane acts as a Lewis base in order to mediate the reaction via the desilylative nucleophilic activation of TMSCN.

Acid-Promoted Intramolecular Decarbonylative Coupling Reactions of Unstrained Ketones: A Modular Approach to Synthesis of Acridines and Diaryl Ketones.

Herein, we reported Lewis acid- or Brønsted acid-promoted intramolecular C(sp2)-C(sp2) bond cleavage and a novel C(sp2)-C(sp2) bond-forming cascade reaction to synthesize the acridine motif. The metal-free oxidation of the alkyne motif generated the in situ ketone group extracted via a decarbonylation reaction. The mechanistic studies revealed that the electrophilic N-iodo species triggered key decarbonylation reactions via consecutive dearomatization/aromatization reactions. In addition, we exploited this acid-promoted C-C bond activation system with internal alkynes to synthesize bis(heteroaryl) ketones.

EPR Studies on the Addition of Ligated Boryl Radicals to Carbonyl Compounds

The boron-centered radicals derived from alkenyl N-heterocyclic carbene (NHC)-boranes bearing ester substituents were recently found to ring close in 5-endo mode by addition to the oxygen atoms of the ester substituents. The inference from this was that NHC-boryl radicals might add intermolecularly to carbonyl-containing substrates. Several different NHC-boryl radicals were generated by H-atom abstraction from NHC-ligated trihydroborates. Electron paramagnetic resonance (EPR) spectroscopy proved that these did indeed add to the oxygen atoms of diaryl ketones with production of the corresponding bora-ketyl radicals. The same unusual regioselectivity of addition was observed with monoaryl ketones, but no bora-ketyls were observed with dialkyl ketones. Similarly, no bora-ketyl adduct radicals were observed with esters, even esters of benzoic acid. EPR spectroscopic evidence suggested that NHC-boryl radicals were also added to the O-atoms of aromatic aldehydes. Amine-boryl and phosphine-boryl radicals were also observed to add to the O-atom of benzophenone with production of the corresponding ketyl radicals.

Heterogeneous Direct Acylation Strategy to Diaryl Ketones and Their Application to 1, 3‐Dihydroisobenzofurans

AbstractAromatic acylation is an indispensable chemical transformation in organic synthesis in affording aryl ketones. In this manuscript, we have described the synthesis of aromatic ketones utilizing graphene oxide (GO) supported PdO nanoparticles (PdO/GO), as heterogeneous transition metal catalyst. The [Pd]‐heterogeneous catalyst enabled the coupling between iodoarenes and aromatic aldehydes. The acylation was carried out by eliminating toxic CO gas as the source of the carbonyl. Further, practicality of this strategy was also demonstrated by fusing 1,3‐dihydroisobenzofurans.