Regio- and stereoselective route to tetrasubstituted olefins by the palladium-catalyzed three-component coupling of aryl iodides, internal alkynes, and arylboronic acids

[reaction: see text] The Pd-catalyzed three-component coupling of readily available aryl iodides, internal alkynes, and arylboronic acids provides a convenient, one-step, regio- and stereoselective route to tetrasubstituted olefins in good to excellent yields, although electron-poor aryl iodides and dialkylalkynes normally afford only low yields under our standard reaction conditions. The proper combination of substrates and reaction conditions is important for high yields. The presence of water generally substantially increases the yields of the desired tetrasubstituted olefins. The reaction involves cis-addition of the aryl group from the aryl iodide to the less hindered or more electron-rich end of the alkyne, while the aryl group from the arylboronic acid adds to the other end. A modified, room-temperature procedure has also been successfully developed, which works very well for some substrates. Tamoxifen and its derivatives are synthesized in a concise, regio- and stereoselective manner by applying our synthetic protocol.     

Preparation of a Nafion-Teflon bimembrane-supported palladium catalyst and its use in the Heck reaction

A novel palladium catalyst supported on the Nafion membrane, reinforced with poly(tetrafluoroethylene) fiber, has been prepared. The catalyst exhibits high activity and stability in the Heck arylation reactions of aryl iodides with olefins and Sonogashira couplings with phenylacetylene, and can be readily recovered and reused twenty times without significant loss of activity.     

N,N′-Mono substituted acyclic thioureas: efficient ligands for the palladium catalyzed Heck reaction of deactivated aryl bromides

A series of N,N′-mono substituted acyclic thiourea ligands are found to be highly active phosphine-free catalysts for palladium catalyzed Heck reaction of aryl iodides and bromides with olefins. We have achieved high turnover numbers for aryl iodides with olefins (TONs up to 970,000 for the reaction of iodobenzene with styrene).     

Vinylation of aryl iodides catalyzed byMCM-41supported poly-g-mercaptopropylsiloxanePd(0,II)complexes

Summary MCM-41-supported poly-γ-mercaptopropylsiloxane palladium (0,II) complexes were easily prepared from poly-γ-mercaptopropylsiloxane and MCM-41 in chloroform, followed by coordination to palladium chloride in ethane at room temperature. These catalysts are highly active and stereoselective for vinylation of aryl iodides with olefins, and give a variety of trans substituted products in high yields at 70^oC, and can be reused without loss in activity.</o:p>     

Sterically bulky thioureas as air- and moisture-stable ligands for pd-catalyzed Heck reactions of aryl halides

We demonstrate that sterically bulky N,N'-disubstituted cyclic thiourea-Pd(0) complexes are air- and moisture-stable and highly active catalysts for palladium-catalyzed Heck reaction of aryl iodides and bromides with olefins (TONs up to 500000 for the reaction of PhI and methyl acrylate). Even activated aryl chlorides can undergo complete conversion in Bu(4)NBr in the presence of 1 mol % Pd catalyst.     

Novel synthesis of fused isoxazolidines via a palladium catalysed allene insertion-intramoleculer 1,3-dipolar cycloaddition cascade reaction

A one pot, three component palladium catalysed allenation of aryl iodides, in combination with a nitrone cycloaddition, leads to formation of fused isoxazolidines, creating two rings, two stereocentres and one tetrasubstituted carbon centre.     

Silica‐supported terpyridine palladium(II) complex as an efficient and reusable catalyst for Heck and Suzuki cross‐coupling reactions

Silica‐supported terpyridine palladium(II) was prepared and used as an effective and recyclable catalyst in Mizoroki–Heck and Suzuki–Miyaura coupling reactions. The catalyst was very effective for the Mizoroki–Heck reaction of aryl halides with olefins and conversion was in most cases excellent. The catalyst showed good thermal stability (up to 230 °C) and could be recovered and reused for four reaction cycles. The Suzuki coupling of aryl iodides with aryl boronic acids in the presence of the catalyst was also investigated and the reaction proceeded with a short reaction time and excellent conversion. Copyright © 2013 John Wiley & Sons, Ltd.     

Palladium‐Catalyzed Decarboxylative γ‐Arylation for the Synthesis of Tetrasubstituted Chiral Allenes

An enantiospecific palladium‐catalyzed decarboxylative coupling of acyclic β,γ‐alkynoic acids with various aryl iodides to chiral tetrasubstituted allenes is described. The coupling reaction comprises a decarboxylative γ‐palladation of α,α‐disubstituted carboxylic acids to provide the tetrasubstituted allenes with complete point‐to‐axial chirality transfer in excellent yields.     

Palladium-catalyzed double arylations of terminal olefins in acetic acid

A palladium-catalyzed Heck diarylation of terminal olefins under ligand-free conditions in acetic acid is described. This procedure allows double arylation of terminal olefins affording trisubstituted olefins in good to excellent yields. The methodology is applicable to the coupling of both electron-deficient and electron-rich aryl iodides leading to symmetrical and unsymmetrical β,β-diarylated alkenes.     

Silica‐coated nano‐Fe3O4‐supported iminopyridine palladium complex as an active,phosphine‐free and magnetically separable catalyst for Heck reactions

A novel magnetic nanoparticle‐supported iminopyridine palladium complex was successfully prepared by attaching palladium acetate to iminopyridine ligand‐functionalized silica‐coated nano‐Fe₃O₄. The as‐prepared catalyst was well characterized and was evaluated in Heck reactions in terms of activity and recyclability. It was found to be highly efficient for the reactions of various aryl iodides and aryl bromides having electron‐withdrawing groups with olefins under phosphine‐free and inert atmosphere‐free conditions. Moreover, the catalyst could be conveniently recovered using an external magnet, and the recyclability was influenced by the base in the Heck reaction. The catalyst could be reused at least six times with no significant loss in activity when triethylamine acted as the base.     

Synthesis of tetrasubstituted naphthalenes by palladium-catalyzed reaction of aryl iodides with internal alkynes

The 1:2 coupling of aryl iodides with acetylenedicarboxylate esters and diphenylacetylene efficiently proceeds in the presence of a palladium catalyst with use of silver carbonate as base to produce the corresponding tetrasubstituted naphthalenes.     

Diversity-oriented synthesis of multisubstituted olefins through the sequential integration of palladium-catalyzed cross-coupling reactions. 2-pyridyldimethyl(vinyl)silane as a versatile platform for olefin synthesis.

A novel strategy for the diversity-oriented synthesis of multisubstituted olefins, where 2-pyridyldimethyl(vinyl)silane functions as a versatile platform for olefin synthesis, is described. The palladium-catalyzed Heck-type coupling of 2-pyridyldimethyl(vinyl)silanes with organic iodides took place in the presence of Pd2(dba)3/tri-2-furylphosphine catalyst to give beta-substituted vinylsilanes in excellent yields. The Heck-type coupling occurred even with alpha- and beta-substituted 2-pyridyldimethyl(vinyl)silanes. The one-pot double Heck coupling of 2-pyridyldimethyl(vinyl)silane took place with two different aryl iodides to afford beta,beta-diarylated vinylsilanes in good yields. The palladium-catalyzed Hiyama-type coupling of 2-pyridyldimethyl(vinyl)silane with organic halides took place in the presence of tetrabutylammonium fluoride to give di- and trisubstituted olefins in high yields. The sequential integration of Heck-type (or double Heck) coupling and Hiyama-type coupling produced the multisubstituted olefins in regioselective, stereoselective, and diversity-oriented fashions. Especially, the one-pot sequential Heck/Hiyama coupling reaction provides an extremely facile entry into a diverse range of stereodefined multisubstituted olefins. Mechanistic considerations of both Heck-type and Hiyama-type coupling reactions are also described.     

Kryptofix 5 as an inexpensive and efficient ligand for the palladium‐catalyzed Mizoroki‐Heck reaction

A novel complex of PdCl₂ with a multidentate cryptand ligand, Kryptofix 5, has been prepared and characterized by various techniques including ¹H‐ and ¹³C NMR spectroscopy, Fourier transform infrared (FT‐IR), Raman, ultraviolet and visible (UV‐VIS) spectroscopy, inductively coupled plasma (ICP), CHN elemental and energy dispersive X‐ray analysis (EDX). This heat‐ and air‐stable complex was utilized as a highly active catalyst for the Mizoroki‐Heck reaction of aryl halides with various olefins. Interestingly, it was found that aryl bromides as well as aryl iodides were efficiently cross‐coupled with terminal alkenes at 130 °C in 10 min. Furthermore, the least reactive aryl chlorides reacted with styrene to obtain the desired products in acceptable yields.     

A novel approach to functionalized (E)-1,4-diaryl-1-butenes by Heck reaction and their applications for the construction of dibenzylbutyrolactone lignan skeletons by radical cyclization

A highly regio- and stereoselective [Pd(allyl)Cl]₂ catalyzed Heck reaction of aryl iodides and electronically neutral terminal olefins generated in situ by fluoride induced protiodesilylation of alkenylsilanol derivatives under mild conditions has been developed. The products, viz. terminally substituted styrenes and (E)-1,4-diaryl-1-butenes were obtained in very good yields. The dibenzylbutyrolactone lignan skeletons have been prepared employing two regio- and stereoselective Bu₃SnH-mediated radical cyclization routes.     

Development of an anomalous Heck reaction: skeletal rearrangement of divinyl and enyne carbinols

[reaction: see text] A general set of conditions that achieves the union of aryl halides and divinyl or enyne carbinols to afford tri- or tetrasubstituted olefins in good yields (up to 83%) is described. The mechanism by which this proceeds is believed to involve the intermediacy of a cyclopropanol, followed by a novel skeletal reorganization. The ability to suppress beta-hydride elimination of organopalladium intermediates appears to be critical to the success of these processes.     

Synthesis of All‐Carbon Quaternary Centers by Palladium‐Catalyzed Olefin Dicarbofunctionalization

The redox‐neutral dicarbofunctionalization of tri‐ and tetrasubstituted olefins to form a variety of (hetero)cyclic compounds under photoinduced palladium catalysis is described. This cascade reaction process was used to couple styrenes or acryl amides with a broad range of highly decorated olefins tethered to aryl or alkyl bromides (>50 examples). This procedure enables one or two contiguous all‐carbon quaternary centers to be formed in a single step. The products could be readily diversified and applied in the synthesis of a bioactive oxindole analogue.     

Highly regioselective internal heck arylation of hydroxyalkyl vinyl ethers by aryl halides in water

Highly regioselective and fast Pd(0)-catalyzed internal alpha-arylation of ethylene glycol vinyl ether with aryl halides was shown to be possible in water without the need for any halide scavengers or ionic liquid additives. This presents, to our knowledge, the first case of water being utilized in the selective arylation of electron-rich olefins. Resulting alpha-products were hydrolyzed and isolated as corresponding acetophenones in good to excellent yields when using aryl bromides and with good to moderate yields in the case of aryl iodides. Microwave irradiation was shown to be beneficial in activation of aryl chlorides toward the internal Heck arylation. The scope of the protocol was further increased to include different hydroxyalkyl vinyl ethers, these all giving selectively only branched alpha-products. Finally, the active role of the hydroxy group in directing the regioselectivity toward internal arylation of electron-rich olefins, even in nonpolar toluene, was revealed.     

Ruthenium-catalyzed ring-closing metathesis to form tetrasubstituted olefins

[structure: see text]. Increased efficiency for ring-closing metathesis to form tetrasubstituted olefins using N-heterocyclic carbene ligated ruthenium catalysts was achieved by reducing the size of the substituents at the ortho positions of the N-bound aryl rings.     

Heck reaction catalyzed by a recyclable palladium supported on shell powder

A novel palladium catalyst supported on shell powder has been prepared, and its application to the Heck reaction of aryl iodides with olefins has been reported. The results showed that the novel catalyst had extremely high activities for the reactions with the average yield over 90%. Also, this catalyst showed excellent stability in Heck reactions, being reused three times. The catalyst was characterized by X‐ray powder diffraction and field‐emission scanned electron microscopy images, and the energy dispersive X‐ray analyzer. Copyright © 2010 John Wiley & Sons, Ltd.     

An efficient,regio- and stereoselective palladium-catalyzed route to tetrasubstituted olefins

An efficient, regio- and stereoselective palladium-catalyzed route to tetrasubstituted olefins has been developed, which involves the intermolecular coupling of an aryl iodide, an internal alkyne, and an arylboronic acid. The reaction involves cis-addition of the aryl group from the aryl halide to the less hindered or less electron-poor end of the alkyne, while the aryl group from the arylboronic acid adds to the other end. [reaction: see text]