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Herein, we describe Hiyama coupling via intramolecular substituent transfer from silicon on one blade of triptycenes to another to yield 1,8,13‐trisubstituted chiral triptycenes. This reaction is attributed to the proximity effect of substituents on triptycene, which plays an important role in not only the formation of the oxy‐palladacycle but also the activation of the silyl group to facilitate σ‐bond metathesis. After bromination and nucleophilic ring opening, the second intramolecular Hiyama coupling provided various 1,8,13‐trisubstituted chiral triptycenes. The optical resolution of 1,8,13‐triptycene afforded an optically active form for the first time. [ABSTRACT FROM AUTHOR]

Application of conventional and ionic liquid (IL) solvents and reagents in the Hiyama cross‐coupling reactions using triazenes as coupling partners was investigated. The microwave‐assisted and Pd‐catalyzed reactions in ROH/HBF4, ROH/BF3 ⋅ Et2O and in [BMIM][X]/[BMIM(SO3H)][OTf]/[BMIM][F] proved effective and gave respectable isolated yields within minutes. The scope of the Hiyama coupling reaction with triazenes was investigated in these media. The IL reagents and solvents were successfully employed to develop stepwise and sequential/tandem Hiyama‐Suzuki (H−S) and Hiyama‐Heck (H−H) methods. Study of the scope of these transformations led to facile synthesis of libraries of biaryls, hetero‐biaryls, diphenylmethanes, styryl‐biphenyls, and a host of biphenyl‐appended heterocycles. The potential for the recycling/reuse of the IL solvents in the Hiyama reaction, and in stepwise and sequential transformations was also examined. [ABSTRACT FROM AUTHOR]

Hiyama cross-coupling is a versatile reaction in synthetic organic chemistry for the construction of carbon–carbon bonds. It involves the coupling of organosilicons with organic halides using transition metal catalysts in good yields and high enantioselectivities. In recent years, hectic progress has been made by researchers toward the synthesis of diversified natural products and pharmaceutical drugs using the Hiyama coupling reaction. This review emphasizes the recent synthetic developments and applications of Hiyama cross-coupling. [ABSTRACT FROM AUTHOR]

Diaryl-substituted vinyl boronates as potent building modules are challenging to synthesize. Herein, we present a convenient strategy based on a gold-catalyzed Hiyama arylation of (Z)-β-(borylvinyl)silanes which are easily accessible by hydroboration of silylalkynes. By exploiting the highly electronegative nature of the Au(III) intermediate (which is accessed by the light-assisted oxidation with aryl diazonium salts), a selective activation of the silyl group in the presence of the boron moiety is achieved. This opens a route to selectively synthesize diaryl-substituted vinyl boronates. The reaction shows a broad substrate range, excellent functional group tolerance and perfect chemo-selectivity. Experimental studies and DFT calculations allowed us to elucidate the mechanism of the reaction, the synthetic potential was demonstrated by downstream transformations providing a facile route to bifunctional phenanthrenes and triaryl-substituted olefins., (© 2024 Wiley‐VCH GmbH.)

An efficient synthesis of C2-aryl pyrimidine derivatives via Pd-catalyzed Hiyama couplings has been developed. Various 2-chloro pyrimidines with electron-donating or electron-withdrawing groups as novel electrophile partners coupled well with trimethoxy(phenyl)silane and vinyltrimethoxysilane in the presence of CuCl and TBAF, providing desired products in good to excellent yields. This procedure showed good functional group tolerance, and the electronic and steric effects of 2-chloro pyrimidines seem to be negligible for the transformation. [ABSTRACT FROM AUTHOR]

A palladium-catalyzed domino Heck cyclization/Hiyama cross-coupling has been achieved for the synthesis of (hetero)aryl-functionalized azaindoline derivatives bearing all-carbon quaternary centers in 46–85% yields. The synthetic versatility of this protocol has been highlighted by the gram-scale synthesis and modification of aryl-containing complex bioactive molecules. [ABSTRACT FROM AUTHOR]

We herein disclose the first Ni-catalyzed Hiyama coupling of aryl halides with vinylsilanes. This protocol uses cheap, nontoxic, and stable vinyltrimethoxysilane as the vinyl donor, proceeds under mild and ligand-free conditions, furnishing a diverse variety of styrene derivatives in high yields with excellent functional group compatibility. [ABSTRACT FROM AUTHOR]

Hiyama cross-coupling is a versatile reaction in synthetic organic chemistry for the construction of carbon–carbon bonds. It involves the coupling of organosilicons with organic halides using transition metal catalysts in good yields and high enantioselectivities. In recent years, hectic progress has been made by researchers toward the synthesis of diversified natural products and pharmaceutical drugs using the Hiyama coupling reaction. This review emphasizes the recent synthetic developments and applications of Hiyama cross-coupling.

The introduction of a biomass-derived ionic liquid into the Hiyama coupling reactions, which has been considered as a powerful tool for the synthesis of symmetrically and non-symmetrically substituted biaryl structures, could further control or even reduce the environmental impact of this transformation. It was shown that tetrabutylphosphonium 4-ethoxyvalerate, a γ-valerolactone-based ionic liquid, can be utilized as an alternative solvent to create carbon–carbon bonds between aryl iodides and functionalized organosilanes in the presence of 1 mol% Pd under typical Hiyama conditions (130 °C, 24 h, tetrabutylammonium fluoride activator). A comparison of different ionic liquids was performed, and the effects of the catalyst precursor and the moisture content of the reaction mixture on the activity of the catalyst system were investigated. The functional group tolerance was also studied, resulting in 15 cross-coupling products (3a–o) with isolated yields of 45–72% and excellent purity (> 98%). [ABSTRACT FROM AUTHOR]

A palladium NNC-pincer complex efficiently catalyzed the direct arylation of thiophene derivatives with extremely low palladium loadings of the order of parts per million. Thus, the reaction of various thiophenes with aryl bromides in the presence of 25–100 mol ppm of chlorido[(2-phenyl-κ- C 2)-9-phenyl-1,10-phenanthroline-κ2- N , N ′]palladium(II) NNC-pincer complex, K2 CO3 , and pivalic acid in N , N -dimethyl-acetamide afforded the corresponding 2- or 5-arylated thiophenes in good to excellent yields. A combination of the present C–H arylation and Hiyama coupling with the same NNC-pincer complex provides an efficient synthesis of unsymmetrical 2,5-thiophenes with catalyst loadings at mol ppm levels. [ABSTRACT FROM AUTHOR]

We report here the use of eucalyptol as a bio-based solvent for Hiyama coupling, cyanation, and multicomponent reactions on O,S,N-heterocycles. These heterocycles were chosen as targets or as starting materials given their biological potential; they play an important role in therapeutically active compounds. Once again, eucalyptol proved to be a credible and sustainable alternative to common solvents.

Supported Au nanoparticles on TiO2 catalyze the unprecedented dehydrogenative disilylation of monosubstituted and 1,1‐disubstituted allenes by Et2SiH2 exclusively on the terminal double bond in a stereoselective manner. Treatment of the disilylation products with H2O, in a one‐pot operation also catalyzed by Au/TiO2, leads to 3‐alkylidene‐1,2,5‐oxadisilolanes, an unknown class of heterocyclic compounds, which are excellent scaffolds for the stereoselective synthesis of alkenes under Hiyama‐type cross‐coupling conditions. [ABSTRACT FROM AUTHOR]

Organoboron compounds are versatile synthetic building blocks. We herein report a new strategy, a photochemical gold‐catalyzed chemo‐selective Hiyama arylation of B,Si bifunctionalized reagents with diazonium salts, which is orthogonal to common strategies and therefore a unique tool for synthesis of valuable biarylboronates. With this new methodology a wide array of diversely functionalized sp2‐ and sp3‐hybridized biarylboronates were obtained. Notably, the synergism of gold catalysis with copper catalysis or palladium catalysis, allows for one‐pot iterative C−X (heteroatom) and C−C couplings for the rapid assembly of several simple fragments to relatively complex molecules. Mechanistic studies indicated that photosensitizer‐free conditions were superior to gold/Ru(bpy)3Cl2 dual catalysis. Organoboron compounds are versatile synthetic building blocks. A new strategy, namely a photochemical gold‐catalyzed chemoselective Hiyama arylation of B,Si bimetallic reagents with diazonium salts, which is orthogonal to common strategies and therefore a unique tool for synthesis of valuable biarylboronates, has been developed. With this new methodology a wide array of diversely functionalized sp2‐ and sp3‐hybridized biarylboronates were obtained. [ABSTRACT FROM AUTHOR]

In situ-generated palladium nanoparticles (Pd NPs) using Triton X-100 non-ionic surfactant-catalyzed one-pot sequential Hiyama and Heck coupling reactions in water under aerobic conditions has been demonstrated. The reaction was highly efficient for the synthesis of symmetrical stillbenes utilizing arenediazonium salts and vinyl triethoxy silane. The in situ-generated Pd NPs were characterized by transmission electron microscopy analysis and had a size below 20 nm. The aqueous system containing the surfactant along with the Pd NPs was recycled five times, without significant loss of catalytic activity. Graphical Abstract: [ABSTRACT FROM AUTHOR]

Chirality, Hiyama coupling, intramolecular reactions, triptycene, sigma-bond metathesis Cover Feature: Intramolecular Hiyama Coupling: Synthesis of 1,8,13-Trisubstituted Chiral Triptycenes with Three Different Substituents by Intramolecular Substituent Transfer (Chem. Eur. J. 39/2023) Keywords: chirality; Hiyama coupling; intramolecular reactions; sigma-bond metathesis; triptycene EN chirality Hiyama coupling intramolecular reactions sigma-bond metathesis triptycene 1 1 1 07/14/23 20230711 NES 230711 B The proximity of Si-O-Pd b plays an important role not only in the formation of the oxy-palladium species in intramolecular Hiyama coupling, but also in the activation of the silyl group to facilitate intramolecular substituent transfer. [Extracted from the article]

Four dinuclear N-heterocyclic carbene (NHC) palladium complexes were prepared by reaction of imidazolinium salts, PdCl2 and bridging ligands (piperazine and DABCO) in one pot or by direct cleavage of the chloro-bridged dimeric compounds [Pd( μ-Cl)(Cl)(NHC)]2 with bridging ligands. All of the complexes were fully characterized using 1H NMR, 13C NMR, high-resolution mass and infrared spectroscopies, elemental analysis and single-crystal X-ray diffraction. The catalytic activities of the obtained palladium catalysts towards of aryl chlorides with phenyltrimethoxysilane were investigated and the results showed that the dinuclear palladium complexes were considerably active for the . Copyright © 2016 John Wiley & Sons, Ltd. [ABSTRACT FROM AUTHOR]

PAMAM dendrimers of generations G2–G3 as well as a partially substituted derivative of generation G4 and a low-molecular-weight tricyclic ligand 4 were used to bind Pd(0) nanoparticles. The obtained adducts were tested as catalysts for C–C cross-coupling reactions, such as the Suzuki-Miyaura, Hiyama, Heck and Sonogashira reaction. The highest yields of the coupling product, diphenylacetylene, were obtained with all the catalysts studied in the Sonogashira coupling performed in ethanol with K2CO3 as base. Very good results, 85–100%, were also found in the Suzuki-Miyaura cross-coupling, while the efficiency of the Hiyama coupling appeared lower, with 38–52% of 2-Methylbiphenyl formed. In all reactions, the G2–Pd(0) catalyst, containing an unmodified dendrimer, afforded the highest yields of the cross-coupling products.

An efficient protocol has been developed for the carbonylative Hiyama coupling of aryl halides using the cesium fluoride as a promoter by palladium-catalyzed in NMP. This protocol was applied to a wide variety of functionalized and hindered aryl iodides and bromides with arylsilanes, to afford the desired biaryl ketones in good to excellent yields. [ABSTRACT FROM AUTHOR]

A versatile palladium-catalyzed tandem synthetic sequence to afford E-stilbenes libraries has been developed. Excellent regio- and stereocontrol have been achieved by means of the sequence of Hiyama and Heck cross-couplings. Undesirable homocoupling byproducts were avoided employing immobilized substrates. [ABSTRACT FROM AUTHOR]

A trimetallic palladium/copper/silver system has been developed that allows the decarboxylative Hiyama coupling of ortho-substituted aryl carboxylates with trialkoxyarylsilanes to give the corresponding biaryls. The cross-coupling is catalyzed by a Pd/N-heterocyclic carbene complex with silver carbonate aiding its reoxidation. Copper(II) fluoride acts as decarboxylation catalyst, stoichiometric oxidant, and fluoride source. The scope of the protocol is demonstrated by 22 examples, among them aryl halides suitable for further coupling, and the synthetic utility of the products is illustrated by their conversion into carbazoles and 1 H-indazoles. [ABSTRACT FROM AUTHOR]

In order to assess relative contribution of steric factors and electron-richness of phosphine ligands on biaryl-type scaffolds, a set of 1-aryl-pyrazole/pyrrole derived ligands L1 – L6 featuring either aryldicyclohexylphosphino or aryldiphenylphosphino donor group was synthesized. A bidentate coordination mode of ligands L1 or L2 was evident from a representative crystal structure that implied a possible hemilabile participation to facilitate catalytic steps. With N-arylpyrroles ( L3 – L5 ), where the second nitrogen donor on the heterocycle is absent, coupling reactions of unactivated chloroarenes still proceeded with comparable efficiency. Thus, suitably endowed triarylphosphines were found to be as efficient as more expensive aryldialkylphosphine analogs in reactions with chloroarenes, extending the scope of ligand design. [ABSTRACT FROM AUTHOR]

The solid-phase version of the Pd-catalyzed Hiyama reaction between a variety of aryltriethoxysilanes and immobilized aryl halides was developed. Smooth cross-coupling was achieved to afford the corresponding biaryl products in moderate to excellent yields. The described protocol would be particularly useful for the construction of 4'-substituted 1,1'-biphenyl derivatives. [ABSTRACT FROM AUTHOR]

A highly regioselective allylic substitution of β-silyl allylic alcohols has been achieved that provides the branched isomer as a single product. This high level of regiocontrol is achieved through the use of a vinyl silane group that can perform a Hiyama coupling providing 1,3-disubstituted allylic amines. An unusual oxidative fragmentation product was also observed at elevated temperature that appears to proceed by a Fleming-Tamao-type oxidation-elimination pathway. [ABSTRACT FROM AUTHOR]

Abstract: The Hiyama C–C coupling reaction of a wide range of aryl iodides and vinylsilanes has been performed using ligand-free solid catalysts based on supported palladium nanoparticles. Among the supports tested (Mg, TiO2, CeO2 and active carbon), the most active catalysts were those in which palladium is supported on MgO and TiO2. Analogous Pt and Au materials were inefficient to promote this reaction. Leaching tests suggest that there is some contribution of dissolved Pd since Pd in solution has been detected and the scavenging test decreases the initial reaction rate. Although the solid Pd catalysts can be reused, it was, however, observed that they undergo a certain deactivation upon use that can be attributed to several factors including the presence of inorganic compounds on the catalyst, Pd leaching or agglomeration of Pd NPs. [Copyright &y& Elsevier]

Cascading chemistry! The first practical relay catalytic cascade intramolecular hydrosiloxylation of arylacetylene and asymmetric Mukaiyama aldol reaction has been established to give synthetically useful products in high yields and with excellent ee (see scheme). [ABSTRACT FROM AUTHOR]

Novel fluorous alkenyl-fluorosilanes (CnF2n+1CH=CHSiMe2F; n = 4, 6, 8; 5a–c) were synthetized in a three step procedure from perfluoroalkyliodides and dimethylvinylchlorosilane. They were first reacted with iodobenzene at room temperature in Hiyama coupling reaction (DMF, Pd(OAc)2, TBAF, 72 h) to afford the appropriate ω-perfluoroalkyl-styrenes (CnF2n+1CH=CHC6H5, n = 4, 6, 8); then the reactivity of 5a with monosubstituted iodobenzenes was studied. The coupling reaction of 5a with o-substituted iodobenzenes usually failed, while that of with the m- and p-substituted ones gave fluorous styrenes [m- or p-(C4F9CH=CH)6H4X], independently of the electronic effect of their substituent (X = Br, CF3, CH3, OCH3). These volatile products can easily be isolated by steam-distilltaion and purified further by distillation. The mechanism of the above coupling reactions was a pure Hiyama type involving fluoride-ion induced transmetallation without any Heck type contribution, since no coupling product of C6F13CH=CH2 and C6H5I was observed in blank control experiments using similar conditions (DMF, TBAF, Pd(OAc)2, 72 h, 25°C). [ABSTRACT FROM AUTHOR]

Abstract: An efficient Hiyama cross-coupling reaction of functionalised styrylsilanes with iodo- and bromobenzene has been performed using complex [PdCl2P(OCH2CMe2NH) OCH2CMe2NH2] as precatalyst. The styrylsilanes underwent cross-coupling reactions with excellent selectivity and yield, up to 99%, of the corresponding E-stilbenes. When (E)-[1-(4-bromophenyl)-2-(1,1,3,3,3-pentamethyldisiloxy)]ethene was used as a source of the silane, a homocoupling reaction took place and polymeric compound containing 0.77% of palladium in the form of Pd(0) nanoparticles was obtained. This material used as a catalyst made it possible to obtain 40% and 38% of the Hiyama cross-coupling product in two subsequent runs. [Copyright &y& Elsevier]

PAMAM dendrimers of generations G2-G3 as well as a partially substituted derivative of generation G4 and a low-molecular-weight tricyclic ligand 4 were used to bind Pd(0) nanoparticles. The obtained adducts were tested as catalysts for C-C cross-coupling reactions, such as the Suzuki-Miyaura, Hiyama, Heck and Sonogashira reaction. The highest yields of the coupling product, diphenylacetylene, were obtained with all the catalysts studied in the Sonogashira coupling performed in ethanol with K2CO3 as base. Very good results, 85-100%, were also found in the Suzuki-Miyaura cross-coupling, while the efficiency of the Hiyama coupling appeared lower, with 38-52% of 2-Methylbiphenyl formed. In all reactions, the G2-Pd(0) catalyst, containing an unmodified dendrimer, afforded the highest yields of the cross-coupling products. [ABSTRACT FROM AUTHOR]

The catalytic activity of two hydrophilic CNC-type palladium pincer complexes is evaluated in the coupling between trimethoxyphenylsilane and aryl bromides. A wide range of assays is performed for each palladium source, and alkaline aqueous conditions turn out to be the most efficient for the target Hiyama coupling, which is applied to the synthesis of several biaryls. In addition, the direct reuse of the aqueous layer containing the catalyst is also conducted with good yield. [ABSTRACT FROM AUTHOR]

Abstract: A new efficient synthetic protocol for the highly stereoselective synthesis of unsymmetrical (or symmetrical) (E)-stilbenes and (E,E)-1,4-diarylbuta-1,3-dienes based on sequential palladium-catalyzed Heck arylation–Hiyama cross-coupling reactions using cyclic gem-bis(silyl)ethene as alkenyl building block is reported. [Copyright &y& Elsevier]

Abstract: A formal synthesis of the antimicrobial tricyclic macrolides, tubelactomicins A and E, featured by a transannular Diels–Alder (TADA) approach, has been explored. The key issue for the transannular cyclization was the synthesis of a 24-membered macrolactone equipped with all the requisite functionalities, which has been achieved using an intramolecular Hiyama cross-coupling strategy. The Hiyama coupling reaction spontaneously triggered off the TADA reaction. From the endo-TADA adduct, formal syntheses of tubelactomicins A and E were achieved. The 24-membered macrolactone formation was also achieved via an intramolecular ring-closing metathesis approach. [Copyright &y& Elsevier]

Abstract: An effective selective silylative coupling functionalization of 1,3,5,7-tetramethyl-1,3,5,7-tetravinylcyclotetrasiloxane with olefins catalyzed by ruthenium-hydride complex [RuHCl(CO)(PCy3)2] has been described. We have obtained numerous unsaturated derivatives of cyclosiloxane possessing a SiCHents (where X=alkyl, aryl, silyl, alkoxy, amine and amide groups). One of the products synthesized (1,3,5,7-tetramethyl-1,3,5,7-tetra-(E)-4-bromostyrylcyclotetrasiloxane) has been efficiently coupled with aryl iodides in the presence of palladium(0) catalyst to yield substituted 4-bromostilbenes. [Copyright &y& Elsevier]

Abstract: A series of new para-substituted (E)-(N)-styrylcarbazoles, i.e., eight (E)-9-[2-(aryl)ethenyl]-9H-carbazoles (5–12) and 1,4-bis[(E)-2-(9H-carbazol-9-yl)vinyl]benzene (13), have been synthesized in high yield and stereoselectively by a sequential silylative coupling–Hiyama coupling reaction, i.e., coupling of commercially available 9-vinylcarbazole with vinyltriethoxysilane or divinyltetramethyldisiloxane in the presence of [RuHCl(CO)(PCy3)2] (I), followed by Pd (II) catalyzed cross-coupling with para-substituted iodobenzenes. The tandem procedure has facilitated the synthesis of 13. X-ray structures of the intermediate silylvinylcarbazole (4), as well as products 12 and 13 have been obtained. [Copyright &y& Elsevier]

Abstract: Phosphites were employed as ligands in palladium-catalyzed Hiyama coupling reactions. The optimized reaction conditions were equimolar amounts (5mol% each) of Pd(acac)2 and phosphite 1 in p-xylene at 80°C with TBAF as an additive. This catalyst system exhibited high activities in the reactions with trimethoxysilylbenzene and aryl bromides that have electron-donating or electron-withdrawing groups. In the case of aryl chlorides, substrates possessing electron-withdrawing groups gave the coupled products in high yields. [Copyright &y& Elsevier]