Hiyama Cross-coupling Reaction Research Articles

Synthesis, characterization and the catalytic application of the N-heterocyclic carbene-PdCl2-cyanopyridine complexes

Six monoligated N-heterocyclic carbene-PdCl2-cyanopyridine complexes were prepared (N-heterocyclic carbene = NHC). X-ray single crystal diffraction analysis indicated that the complexes showed mononuclear Pd–NHC structures with two chlorides and the N-donor from cyanopyridine as ancillary ligands. The lengths of the Pd–C bonds in all complexes were 1.959(5)–1.976(3) Å, comparable to those found in the corresponding Pd–NHC catalysts. The catalytic activities of the well-defined Pd–NHC complexes have been evaluated with respect to the Hiyama cross-coupling reactions of aryl trialkoxysilanes with aryl chlorides. With 1.0 mol% Pd-catalyst, all synthesized palladium compounds have shown moderate to good catalytic activities for the coupling reactions.

Biogenically synthesized palladium nanoparticles for hydrogen evolution study: An efficient catalyst for 4-nitrophenol reduction and C-C coupling reactions

Indian cork extract is employed for the greener production of palladium nanoparticles (Pd NPs) an effective heterogeneous catalyst with a concentration of 30.1%. Plant extract-mediated phytochemicals were found responsible for reducing Pd(II) to Pd(0) without the aid of an external reducing agent. XRD, UV–visible, and other analyses demonstrated the successful formation of Pd NPs. These NPs were evident to have better electrocatalytic activity in the hydrogen evolution reaction (HER) in an acidic medium. The Tafel slope (174 mV/dec) of the Pd NPs catalyst confirmed the Volmer-Heyrovsky mechanism for HER study and demonstrated the electrochemical desorption of hydrogen is the rate-determining step. In terms of synthetic organic chemistry perspectives, the applicability of Pd NPs has been subsequently demonstrated for the reduction of toxic 4-nitrophenol to synthetically important 4-aminophenol with a minimum catalyst loading at ambient conditions. Additionally, the outstanding catalytic activity of synthesized heterogeneous Pd NPs catalyst has been showcased for direct Heck and Hiyama cross-coupling reactions.

Stereoselective Palladium-Catalyzed Hiyama Cross-Coupling Reaction of Tetrasubstituted gem-Difluoroalkenes.

We herein describe a diastereoselective Pd(0)-catalyzed Hiyama cross-coupling reaction of gem-difluoroalkenes. The use of organosilicon reagents in this reaction is advantageous over other organometallic reagents by allowing the introduction of a wide range of functional groups, including challenging alkyl groups. Also conveniently, the additive TBAF was not required for (hetero)aryl-substituted difluoroalkenes.

Computational and Experimental Design of the Octahedral PdFe Alloy Nanocatalyst for Hiyama Cross-Coupling and Environmental Pollutant Degradation

The research on various bimetallic nanoparticles (NPs) is rapidly expanding due to their widespread applications. However, the formation of bimetallic nanostructures in a facile way remains challenging. In the present study, an octahedral (Oh) PdFe alloy nanostructure was designed by following an aqueous medium synthesis strategy. Different metal precursor ratios were varied to observe the change in the shape and distribution of the Oh PdFe alloy nanostructure. Surprisingly, increasing the Fe content directed the finer growth of Oh morphology. However, increasing the Pd amount resulted in an uneven Oh PdFe alloy shape. The catalytic activity of the optimized Oh PdFe alloy was examined for Hiyama cross-coupling, and the degradation of dyes was scrutinized at different pH. The suggested alloy nanostructured catalyst exhibited improved catalytic behavior compared to other nanocatalysts, such as commercial catalyst Pd/C (95%), monometallic Pd Oh (98%), Fe NPs (15%), and PdFe NPs (85%), for the Hiyama cross-coupling reaction. The optimized alloy catalyst with less Pd and more Fe demonstrated 98% yield and excellent reusability up to the fifth consecutive cycle, conveying 80% yield. The stability of the Oh PdFe alloy nanocatalyst and the mechanistic aspects of Hiyama cross-coupling was supported by density functional theory. The degradation of both anionic dyes, Congo red, Eosin Y, and cationic rhodamine B, was performed under normal along with acidic and basic conditions. The degradation reaction was completed in an adequate time interval for all the dyes with no change in the morphology of the synthesized catalyst.

Magnetic nanoparticles embedded hexagonal boron nitride tethered N-heterocyclic carbene-palladium(II): An efficient and reusable magnetic catalyst for fluoride-free Hiyama cross-coupling and 4-nitrophenol reduction reactions

Heterogeneous catalysts have a wide range of applications on a commercial scale and are thus favored over their homogeneous analogs due to their stability and recyclability. However, their key drawback is poor reactivity. Consequently, the need to design heterogeneous catalysts with enhanced activity is a pressing matter. In this work, a new heterogeneous catalyst, magnetic nanoparticles embedded hexagonal boron nitride tethered N-heterocyclic carbene-palladium(II) (MNP-h-BN@NHC–Pd), was synthesized using a cost-effective and facile approach under aerobic conditions. The magnetic catalyst was characterized to confirm its structure, morphology, chemical composition, and thermal stability using various analytical techniques. The synthesized magnetic MNP-h-BN@NHC–Pd catalyst was studied in terms of its catalytic ability in the fluoride-free Hiyama cross-coupling reaction and recycled up to six cycles without any significant loss of activity. In addition, the catalytic application of the magnetic MNP-h-BN@NHC–Pd catalyst was further explored for the reduction of 4-nitrophenol (4-NP), a contaminant found in industrial wastewater, with a recyclability of up to nine cycles. The recovery of the magnetic MNP-h-BN@NHC–Pd catalyst from the reaction medium was achieved by use of an external magnetic field and the recycled magnetic catalyst did not show any drastic change in its chemical structure or morphology.

Silyl Radical Cascade Cyclization of 2-Isocyanothioanisole toward 2-Silylbenzothiazoles through Radical Initiator-Inhibitor Symbiosis.

A demethylative silyl radical cascade cyclization of 2-isocyanothioanisoles toward 2-silylated benzothiazole building blocks has been developed. The development of a "radical initiator-inhibitor symbiosis" system solves the challenge of otherwise dominant methyl radical-triggered side reactions brought about by kinetically unfavored generation of reactive silyl radical species. The products accessed in this protocol are amendable to various downstream functionalization reactions, including the quick construction of a topoisomerase II inhibitor via a Hiyama cross-coupling reaction and of an antiviral agent via a fluoride-/hydroxide-free nucleophilic substitution to acyl chloride.

Copper-Promoted Hiyama Cross-Coupling of Arylsilanes With Thiuram Reagents: A Facile Synthesis of Aryl Dithiocarbamates.

We report herein a facile Hiyama cross-coupling reaction of arylsilanes with thiuram reagents (tetraalkylthiuram disulfides or tetraalkylthiuram monosulfide) enabled by copper fluoride. Compared to our previous work, this protocol is an alternative protocol for the generation of S-aryl dithiocarbamates. It features low toxic and readily available substrates, cost-effective promoter, easy performance, and provides good yields.

A Copper(I)-Catalyzed Sulfonylative Hiyama Cross-Coupling.

An air-tolerant Cu-catalyzed sulfonylative Hiyama cross-coupling reaction enabling the formation of diaryl sulfones is described. Starting from aryl silanes, DABSO and aryliodides, the reaction tolerates a large variety of polar functional groups (amines, ketones, esters, aldehydes). Control experiments coupled with DFT calculations shed light on the mechanism, characterized by the formation of a Cu(I)-sulfinate intermediate via fast insertion of a SO2 molecule.

Facile Approach to C-Glucosides by Using a Protecting-Group-Free Hiyama Cross-Coupling Reaction: High-Yielding Dapagliflozin Synthesis.

Access to unprotected (hetero)aryl pseudo-C-glucosides via a mild Pd-catalysed Hiyama cross-coupling reaction of protecting-group-free 1-diisopropylsilyl-d-glucal with various (hetero)aryl halides has been developed. In addition, selected unprotected pseudo-C-glucosides were stereoselectively converted into the corresponding α- and β-C-glucosides, as well as 2-deoxy-β-C-glucosides. This methodology was applied to the efficient and high-yielding synthesis of dapagliflozin, a medicament used to treat type 2 diabetes mellitus. Finally, the versatility of our methodology was proved by the synthesis of other analogues of dapagliflozin.

Dissecting Transmetalation Reactions at the Molecular Level: Role of the Coordinated Anion in Gas-Phase Models for the Transmetalation Step of the Hiyama Cross-Coupling Reaction

Palladium-catalyzed cross-coupling protocols have become a cornerstone in organic synthesis. Here, a gas-phase model of the Hiyama cross-coupling reaction was designed to shed light on the roles of coordinated anions (fluoride versus chloride) in transmetalation from Si to Pd. A combination of mass spectrometry experiments and DFT calculations was used. The ligated palladium fluoride and chloride cationic complexes, [(phen)Pd(X)]+ (X = F and Cl), readily react with vinyltrimethylsilane, Me3Si(CH═CH2), via transmetalation to give [(phen)Pd(CH═CH2)]+ as the major product. DFT calculations reveal that this transmetalation reaction is concerted and proceeds via a four-centered transition state, illustrating the role of coordinated halide in this gas-phase system. Two minor side products are observed corresponding to transmetalation to give [(phen)Pd(CH3)]+ and [(phen)Pd(SiMe2X)]+. DFT calculations suggest that these arise from the same initial Si to Pd methyl transmetalation pathway to give the [(phen)Pd(CH3) + Me2(CH═CH2)SiX]+ intermediate, which either then loses Me2(CH═CH2)SiX or reacts via C–C bond coupling to ultimately yield propene and [(phen)Pd(SiMe2X)]+. [(phen)Pd(CH═CH2)]+ undergoes a reaction with a second molecule of vinyltrimethylsilane to form an adduct, which upon collision-induced dissociation liberates 1,3-butadiene to form [(phen)Pd(SiMe3)]+. DFT calculations suggest a mechanism in which C–C bond formation is followed by migration of SiMe3 from C to Pd. Links between the observed gas-phase chemistry and solution-phase Pd-mediated homocoupling reactions of vinyltrimethylsilanes are explored.

Competition between the Hiyama and Suzuki–Miyaura Pd-catalyzed cross-coupling reaction mechanisms for the formation of some regioselective derivatives of quinoxaline and benzofuran; Which reaction mechanism is more favorable?

Pd-NHC type complexes are supposed to have a high degree of participation in ‘C–C’ cross-coupling reactions, so they are commonly used in industry as well as academia. As regards the competition between Hiyama and Suzuki-Miyaura, this research aims to establish a more suitable reaction pathway and cross-coupling mechanism for the formation of certain derivatives of quinoxaline and benzofuran at the Cam-B3LYP-D3 theoretical level. First of all, the 2-phenyl-toluene formation cycle was determined using two specified cross-coupling reactions due to the presence of experimental 2-phenyl-toluene formation data in both Suzuki-Miyaura and Hiyama cross-coupling reactions. The mechanisms for the development of regioselective compounds 2-(2-methoxyphenyl)-6-p-tolylquinoxaline and 2,3-bis (4-chlorophenyle) benzofuran by Suzuki-Miyaura and Hiyama cross-coupling reactions are computationally compared to more suitable reaction pathways and cross-coupling reactions. In particular, our findings are consistent with the Pd-NHC type complex approach to this problem, which is more desirable for the development of regioselective compounds in competition between the various types of cross-coupling reaction mechanisms.

Palladium-Catalyzed Hiyama Cross-Couplings of Arylsilanes with 3-Iodoazetidine: Synthesis of 3-Arylazetidines.

The first palladium-catalyzed Hiyama cross-coupling reactions of arylsilanes with 3-iodoazetidine were described. The protocol provides a convenient access to a variety of useful 3-arylazetidines which are of great interest in pharmaceutical laboratories in moderate to good yields (30%-88%). In addition, this strategy has the advantage of easy operation and mild reaction conditions.

Highly Enantioselective Hiyama Cross-Coupling via Rh-Catalyzed Allylic Arylation of Racemic Allyl Chlorides.

Highly enantioselective Hiyama cross-coupling reactions have been achieved through rhodium(I)-catalyzed dynamic kinetic asymmetric transformations between aryl siloxanes and cyclic racemic allyl halides. This process affords valuable enantiomerically enriched aryl-substituted cyclic allyl products and is compatible with heterocyclic allyl chloride electrophiles.

Recent advances in the application of nano-catalysts for Hiyama cross-coupling reactions.

This mini-review highlights the recent developments in the field of metal nanoparticle (NP) catalyzed Hiyama cross-coupling reactions. Most of the nanocatalysts outlined here allow convenient and green synthetic pathways for the construction of carbon–carbon bonds in water and fluoride-free conditions. Literature has been surveyed from 2005 to February 2018.

SO2 conversion to sulfones: development and mechanistic insights of a sulfonylative Hiyama cross-coupling.

A Pd-catalyzed Hiyama cross-coupling reaction using SO2 is described. The use of silicon-based nucleophiles leads to the formation of allyl sulfones under mild conditions with a broad functional group tolerance. Control experiments coupled with DFT calculations shed light on the key steps of the reaction mechanism, revealing the crucial role of a transient sulfinate anion.

α-Arylation of Amides from α-Halo Amides Using Metal-Catalyzed Cross-Coupling Reactions

Metal-catalyzed α-arylation of amides from α-halo amides with organometallic reagents is reviewed. The article includes Suzuki–Miyaura, Kumada–Corriu, Negishi, and Hiyama cross-coupling reactions.1 Introduction2 Suzuki–Miyaura Cross-Coupling2.1 Palladium Catalysis2.2 Nickel Catalysis3 Kumada–Corriu Cross-Coupling3.1 Nickel Catalysis3.2 Iron Catalysis3.3 Cobalt Catalysis4 Negishi Cross-Coupling5 Hiyama Cross-Coupling6 Conclusion

Synthesis of chiral \u03b1-trifluoromethyl alcohols and ethers via enantioselective Hiyama cross-couplings of bisfunctionalized electrophiles

Methods for synthesis of chiral organic compounds bearing trifluoromethyl-substituted stereocenters are of great interest for agrochemical and pharmaceutical labs and industries in their search for new bioactive materials. We report on employment of bisfunctionalized electrophiles, bearing both a trifluoromethyl and a functional group as direct substituents of the reactive center, in cross-coupling reactions. We exemplify this concept in the asymmetric synthesis of enantioenriched α-trifluoromethyl- and perfluoroalkyl-containing benzylic and allylic ethers and alcohols by nickel-catalyzed stereoconvergent Hiyama cross-coupling reaction. Substrate electrophiles are conveniently prepared in few steps from trifluoroacetic acid. The method represents a conceptually different approach to chiral CF3-substituted alcohols and ethers and allows for a rapid catalytic preparation of a wide range of these valuable compounds in high yields and enantioselectivity.

New insight in Hiyama cross-coupling reactions: Decarboxylative, denitrogenative and desulfidative couplings

In this mini-review, recent advances and developments in the decarboxylative, denitrogenative, and desulfidative Hiyama-type cross-coupling reaction from 2011 up present are studied. This review focused mainly on mechanistic aspects of Hiyama cross-coupling reactions

Green Synthesis of Palladium Nanoparticles: Applications in Aryl Halide Cyanation and Hiyama Cross-Coupling Reaction Under Ligand Free Conditions

In the current work, palladium nanoparticles (Pd NPs) were prepared from palladium acetate biogenically using the aqueous-ethanolic extract of black pepper (Piper nigrum) and characterized by various analytical techniques like XRD, FE-SEM, EDS, TEM, ATR-IR, UV–Vis spectroscopy, BET, TGA and ICP-OES analysis. The reduction of Pd(II) to Pd(0) is achieved by the action of various phytochemicals present in the black pepper extract like phenols, acids, pellitorine, ethyl piperonyl cyanoacetate, piperine and N-isobutyl-tetradeca-2,4-dienamide. The biosynthesized Pd NPs shown excellent catalytic activity in aryl halide cyanation and Hiyama cross-coupling reactions. Also, less toxic potassium hexacyanoferrate(II) trihydrate was used as cyanide source in aryl halide cyanation and Hiyama cross-coupling was performed under fluoride free condition. Both reactions proceeded well with Pd NPs under ligand free circumstances to give good to excellent yields. The Pd NPs were recovered after each reaction and recycled up to five times in aryl halide cyanation and ten times in Hiyama cross-coupling without considerable loss in the activity. Green synthesis of palladium nanoparticles: applications in aryl halide cyanation and Hiyama cross-coupling reaction under ligand free conditions.

Synthesis of substituted Z-styrenes by Hiyama-type coupling of oxasilacycloalkenes: application to the synthesis of a 1-benzoxocane.

Several Hiyama cross-coupling reactions of oxasilacycloalkenes and aryl iodides are described that produce trisubstituted Z-styrenes in moderate to excellent yields. Both electron-rich and electron-poor aryl iodides are tolerated in the cross-coupling reaction. The oxasilacycloalkene coupling partners were prepared by ruthenium-catalyzed intramolecular anti-hydrosilylation of alkynols. One of the cross-coupling products was converted to a 1-benzoxocane, albeit in low yield, using an intramolecular Buchwald–Hartwig etherification. The cyclic ether produced contains the carbon skeleton of heliannuol A.