Showing papers on "Heck reaction published in 2011"
402 citations
TL;DR: An environmentally benign surfactant (TPGS-750-M), a diester composed of racemic α-tocopherol, MPEG-750, and succinic acid, has been designed and readily prepared as an effective nanomicelle-forming species for general use in metal-catalyzed cross-coupling reactions in water.
Abstract: An environmentally benign surfactant (TPGS-750-M), a diester composed of racemic α-tocopherol, MPEG-750, and succinic acid, has been designed and readily prepared as an effective nanomicelle-forming species for general use in metal-catalyzed cross-coupling reactions in water. Several “name” reactions, including Heck, Suzuki−Miyaura, Sonogashira, and Negishi-like couplings, have been studied using this technology, as have aminations, C−H activations, and olefin metathesis reactions. Physical data in the form of DLS and cryo-TEM measurements suggest that particle size and shape are key elements in achieving high levels of conversion and, hence, good isolated yields of products. This new amphiphile will soon be commercially available.
334 citations
TL;DR: In this paper, transition-metal-catalysed and -mediated processes for the preparation of oxindoles from anilides through C(3)-C(3a) bond formation are described.
269 citations
TL;DR: In this paper, the authors highlight the potential and the versatility of arenediazonium salts as viable alternatives to conventional aryl halides and oxygen-based electrophiles for Pd-catalyzed Heck reactions.
245 citations
TL;DR: In this paper, a new hybrid material, PdNPs@CNCs, consisting of monodisperse Pd nanoparticles (PdNs) evenly deposited onto colloidal cellulose nanocrystallites, was presented.
226 citations
TL;DR: A palladium-based catalyst supported on amine-functionalized magnetite nanoparticles was successfully prepared by a facile one-pot template-free method combined with a metal adsorption-reduction procedure as discussed by the authors.
194 citations
TL;DR: An efficient magnetic carbon nanocomposite supported Pd nanoparticle catalyst has been prepared by a three-step process in this article, where the morphology, inner structure, and magnetic properties of a...
Abstract: An efficient magnetic carbon nanocomposite supported Pd nanoparticle catalyst has been prepared by a three-step process in this report. The morphology, inner structure, and magnetic properties of a...
189 citations
TL;DR: It is reported that cheaper and greener alcohols allow the Heck arylation of electron-rich olefins to proceed in a much faster, productive, and totally α-regioselective manner, circumventing the need for an ionic medium or hydrogen bond donor salt.
Abstract: The Pd-catalyzed Mizoroki–Heck reaction of olefins with aryl halides, more often simply called the Heck reaction, was recently recognized with the 2010 Nobel Prize in chemistry. Although highly selective with electron-deficient olefins, which generally yield the linear β-arylated product exclusively, the Heck reaction is less satisfactory with electron-rich olefins. This substrate typically generates a mixture of both α- and β-arylated regioisomeric products, hampering wider application of the reaction in chemical synthesis.Pioneering studies by a number of researchers revealed that high α-regioselectivity could be obtained under Pd–diphosphine catalysis either through (i) the substitution of aryl triflates for halides or (ii) the addition of stoichiometric silver or thallium salts when aryl halides are used. Under these conditions, the arylation is believed to proceed via an ionic pathway. However, silver introduces added cost, thallium salts are toxic, and triflates are generally commercially unavailabl...
186 citations
TL;DR: In this paper, an efficient heterogeneous catalyst system based on the immobilization of Pd nanoparticles on a silica-starch substrate (PNP-SSS) is reported.
151 citations
TL;DR: The regioselectivity predicted for a number of monosubstituted benzenes is in excellent agreement with experimental observations, lending further support for the proposed mechanism for Pd(II)-catalyzed oxidative cross-coupling between electron-deficient arenes and alkenes.
Abstract: A systematic theoretical study is carried out on the mechanism for Pd(II)-catalyzed oxidative cross-coupling between electron-deficient arenes and alkenes. Two types of reaction pathways involving either a sequence of initial arene C-H activation followed by alkene activation, or the reverse sequence of initial alkene C-H activation followed by arene activation are evaluated. Several types of C-H activation mechanisms are discussed including oxidative addition, σ-bond metathesis, concerted metalation/deprotonation, and Heck-type alkene insertion. It is proposed that the most favored reaction pathway should involve an initial concerted metalation/deprotonation step for arene C-H activation by (L)Pd(OAc)(2) (L denotes pyridine type ancillary ligand) to generate a (L)(HOAc)Pd(II)-aryl intermediate, followed by substitution of the ancillary pyridine ligand by alkene substrate and direct insertion of alkene double bond into Pd(II)-aryl bond. The rate- and regio-determining step of the catalytic cycle is concerted metalation/deprotonation of arene C-H bond featuring a six-membered ring transition state. Other mechanism alternatives possess much higher activation barriers, and thus are kinetically less competitive. Possible competing homocoupling pathways have also been shown to be kinetically unfavorable. On the basis of the proposed reaction pathway, the regioselectivity predicted for a number of monosubstituted benzenes is in excellent agreement with experimental observations, thus, lending further support for our proposed mechanism. Additionally, the origins of the regioselectivity of C-H bond activation is elucidated to be caused by a major steric repulsion effect of the ancillary pyridine type ligand with ligands on palladium center and a minor electronic effect of the preinstalled substituent on the benzene ring on the cleaving C-H bond. This would finally lead to the formation of a mixture of meta and para C-H activation products with meta products dominating while no ortho products were detected. Finally, the multiple roles of the ancillary pyridine type ligand have been discussed. These insights are valuable for our understanding and further development of more efficient and selective transition metal-catalyzed oxidative C-H/C-H coupling reactions.
138 citations
TL;DR: A Pd-catalyzed desulfitative Heck-type reaction of aromatic sulfinic acid sodium salts with various olefins with the presence of phosphane ligand DPEphos in anisole can significantly enhance the reaction selectivity.
TL;DR: Preliminary mechanistic studies demonstrate that the σ-donating DMA solvent is crucial for high selectivity and suggest that the catalyst distinguishes between β-hydrogens on the basis of their relative hydridic character, in contrast to previously reported Pd(II)-catalyzed oxidative reaction conditions.
Abstract: Simple, mild, and efficient conditions are reported for a Pd0-catalyzed Heck reaction that delivers high yields and selectivity for (E)-styrenyl products using electronically nonbiased olefin substrates bearing a range of useful functionality. Preliminary mechanistic studies demonstrate that the σ-donating DMA solvent is crucial for high selectivity. Further studies suggest that the catalyst distinguishes between β-hydrogens on the basis of their relative hydridic character, in contrast to previously reported PdII-catalyzed oxidative reaction conditions.
TL;DR: A palladium-catalyzed iodine atom transfer cycloisomerization of (Z)-1-iodo-1,6-diene has been developed, which provides a facile method to construct six-memebered heterocycles bearing an alkyl iodide group.
Abstract: A palladium-catalyzed iodine atom transfer cycloisomerization of (Z)-1-iodo-1,6-diene has been developed, which provides a facile method to construct six-memebered heterocycles bearing an alkyl iodide group. The ligand screening shows that both the type and the quantity of ligand impose significant influences on this transformation, and the combination of 30 mol % 1,1'-bis(diphenylphosphino)ferrocene (DPPF) and 10 mol % Pd(OAc)(2) is the optimal choice. The catalytic cycle, consisting of oxidative addition of Pd(0) to vinyl iodide, intramolecular alkene insertion, and alkyl iodide reductive elimination, has been proposed and eventually supported by convincing evidence from a series of control experiments. More importantly, these control experiments disclose some features of the event of alkyl iodide reductive elimination: (1) this reductive elimination is proved to be a stereospecific process; and (2) both alkyl iodide oxidative addition and reductive elimination are not effected by a TEMPO additive. Besides its ability to undergo oxidative addition, the catalyst (palladium + DPPF) could also promote a radical transfer process. The findings described in this paper will be helpful for further development of the metal-catalyzed formation of a carbon-halide bond.
TL;DR: Several chitosan and 6-deoxy-6-amino chitOSan-Schiff base ligands were prepared by condensation of either 2-pyridinecarboxaldehyde or 2-(diphenylphosphino)benzaldehyde with the amino group(s) on chitosa and its derivative (6-deox-6amino CHITosan).
Abstract: Several chitosan and 6-deoxy-6-amino chitosan-Schiff base ligands ( 1 – 4 ) were prepared by condensation of either 2-pyridinecarboxaldehyde or 2-(diphenylphosphino)benzaldehyde with the amino group(s) on chitosan and its derivative (6-deoxy-6-amino chitosan). The supported ligands were reacted with [PdCl 2 (COD)] to form chitosan-supported Pd II catalysts ( 5 – 8 ). All the supported catalysts were air- and moisture-stable and have been characterized using elemental analysis, ICP-MS, UV–vis, FT-IR, PXRD, TGA, 31 P solid state NMR and TEM. As models for the heterogenized catalysts ( 5 and 6 ), mononuclear Pd II complexes ( 9 and 10 ) were also prepared via the Schiff-base condensation reaction of 1,3,4,6-tetra- O -acetyl-β- d -glucosamine hydrochloride to form 1,3,4,6-tetra- O -acetyl-β- d -glucos-2-pyridylimine and 1,3,4,6-tetra- O -acetyl-β- d -glucos-2-(diphenylphosphino)imine which were subsequently reacted with [PdCl 2 (COD)]. Complexes ( 9 and 10 ) and their precursors were characterized by 1 H and 31 P NMR, UV–vis, FT-IR spectroscopy and elemental analysis. Catalytic Suzuki–Miyaura and Heck carbon–carbon cross-coupling reactions were carried out using the supported Pd catalysts and their mononuclear analogues. The immobilized and homogeneous catalysts showed high activity for both the Suzuki–Miyaura and Heck cross-coupling reactions in organic and aqueous media. Homogeneous catalysts ( 9 and 10 ) decomposed during the first run, while the supported catalysts could be recycled and reused up to five times.
TL;DR: A new efficient method for the direct alkenylation of chromones via a palladium(II)-catalyzed C-H functionalization reaction was developed and afforded various 3-vinylchromone derivatives, which are privileged structures in many biologically active compounds and versatile synthetic building blocks.
TL;DR: An efficient Pd-catalyzed Heck reaction of aryl chlorides with olefins with high yields of products was achieved with n-Bu(4)N(+)OAc(-) as base.
Abstract: An efficient Pd-catalyzed Heck reaction of aryl chlorides with olefins under mild conditions is described. High yields of products were achieved with n-Bu4N+OAc– as base. Significantly, the temperature of the Heck reaction of diverse nonactivated aryl chlorides can be lowered to 80 °C. The new reaction system can also tolerate a wider range of olefins.
TL;DR: Application to isotope labeling, incorporating (13)CO, was further established and an effective exploitation of the hazardous CO gas is obtained affording chalcone derivatives in good yields.
TL;DR: In this article, the PAMAM-grafted-MWCNTs (PAMAMg-mwcNTs) hybrid materials were obtained and their application as a new nanocatalyst toward Heck reaction in different conditions was investigated.
Abstract: Polyamidoamine (PAMAM) dendrimers up to the third generation (G) were grown onto the surface of functionalized multiwall carbon nanotubes (MWCNTs-NH 2 ) by a divergent method, the PAMAM-grafted-MWCNTs (PAMAM-g-MWCNTs) hybrid materials were obtained. Because of the surface modification of the multiwall carbon nanotubes with PAMAM dendrimers, these hybrid materials are not only soluble in aqueous medium but also are able to trap water soluble metal ions such as Pd 2+ via complex formation of PAMAM dendrimer with metal ions. The reduction of trapped palladium ions in the dendritic shell of PAMAM-g-MWCNTs by sodium borohydride led to immobilized palladium nanoparticles on the surface of MWCNTs. Thus, palladium nanoparticles were immobilized by PAMAM-g-MWCNTs hybrid materials (PdNs-PAMAM-g-MWCNTs) and their application as a new nanocatalyst toward Heck reaction in different conditions was investigated. The G3 and G2 hybrid materials were found to be very active in cross-coupling reactions of aryl iodides, bromides and also chlorides with olefinic compounds in Heck reactions with short reaction time duration and high yields. The catalyst can be recycled several times without loss in activity.
TL;DR: In this article, a hydrophobic palladium complex of the chelating N-heterocyclic dicarbene (NHDC) was synthesized through in situ deprotonation of a bisimidazolium salt by Pd(OAc)2 in DMSO, subsequent basic hydrolysis and acidification resulted in the formation of four NHDC palladium complexes bearing carboxylic functional groups.
TL;DR: A short and efficient synthesis of a bis-NHC-palladium catalyst simply prepared from caffeine in two steps was reported in this article, which can be used as a good catalyst in running Suzuki-Miyaura, Mizoroki-Heck, and Sonogashira reactions in aqueous solution.
TL;DR: Pd(OAc)(2)/3 is an efficient catalyst system for the base-free oxidative Heck reaction that outperforms the currently available catalysts for the more challenging substrates studied.
Abstract: Pd(OAc)(2)/3 is an efficient catalyst system for the base-free oxidative Heck reaction that outperforms the currently available catalysts for the more challenging substrates studied. The catalyst system is highly selective, and works at room temperature with dioxygen as the oxidant.
TL;DR: Extension of the delocalized π-electron system accomplished by Heck coupling reactions with aryl halides results in an increased fluorescence of the compounds whose applicability is yet to be established.
TL;DR: A simple and expedient process for the Heck aminocarbonylative synthesis of Weinreb and MAP amide acylating agents, from aryl halides, is reported.
Abstract: A simple and expedient process for the Heck aminocarbonylative synthesis of Weinreb and MAP amide acylating agents, from aryl halides, is reported. This methodology utilizes solid sources of CO making it readily accessible to chemists working in small-scale laboratory applications.
TL;DR: An efficient and versatile approach for the synthesis of 2-deoxy-C-aryl glycosides is reported, based on a palladium-catalyzed decarboxylative Heck coupling reaction of benzoic acids and glycals.
TL;DR: The Heck reaction of aryl iodides with allylic alcohols under aerobic conditions in water is described in this article, and a two-step one-pot process, involving a Heck reaction followed by an enantioselective enzyme-catalyzed reduction, is applied to the synthesis of (R)-(−)-rhododendrol.
Abstract: The use of phosphine-free perfluoro-tagged palladium nanoparticles immobilized on fluorous silica gel (FSG), either through fluorous–fluorous interactions or covalent bonding, in the Heck reaction of aryl iodides with allylic alcohols under aerobic conditions in water is described. 4-(4-Methoxyphenyl)-butan-2-one, an important fine chemical, is readily accessed by this procedure. A two-step one-pot process, involving a Heck reaction followed by an enantioselective enzyme-catalyzed reduction, to form chiral alcohols is applied to the synthesis of (R)-(−)-rhododendrol. The palladium catalysts can be recycled several times, both in the Heck reaction and in the one-pot chemoenzymatic process.
TL;DR: A catalytic system is presented that selectively switches between conjugate addition and the Mizoroki-Heck reaction of aryl halides with Michael acceptors, which avoids the preparation and use of organometallics.
Abstract: Ace of base: A catalytic system is presented that, solely by choice of the base, selectively switches between conjugate addition and the Mizoroki-Heck reaction of aryl halides with Michael acceptors (see scheme; R, R' = alkyl, aryl). For conjugate addition reactions, this avoids the preparation and use of organometallics.
TL;DR: In this paper, a new palladium grafted mesoporous organic polymer catalyst has been synthesized through the reaction of palladium(II) acetate with mesophorous poly-triallylamine (MPTA-1) in methanol.
Abstract: A new palladium grafted mesoporous organic polymer catalyst has been synthesized through the reaction of palladium(II) acetate with mesoporous poly-triallylamine (MPTA-1) in methanol. Powder XRD, HR TEM, FE SEM-EDS, AAS, UV–vis spectroscopic tools are employed to characterize this supported palladium catalyst Pd–MPTA-1. The Heck coupling reactions between a series of aryl halides and alkenes have afforded the corresponding C–C coupling products in good yield over this Pd-catalyst using water as reaction medium. This protocol provides a simple strategy for the generation of a variety of new C–C bonds by using this recyclable heterogeneous catalyst under environmentally benign conditions.
TL;DR: A superparamagnetic solid catalyst has been successfully synthesized by loading palladium nanoparticles into the pore network of a mesoporous NiFe 2 O 4 support (Pd/NF300), which was used as a magnetically separable and highly active catalyst for Suzuki and Heck C-C coupling reactions as mentioned in this paper.
Abstract: A superparamagnetic solid catalyst has been successfully synthesized by loading palladium nanoparticles into the pore network of a mesoporous NiFe 2 O 4 support (Pd/NF300), which was used as a magnetically separable and highly active catalyst for Suzuki and Heck C–C coupling reactions. Various techniques were employed to characterize the synthesized NiFe 2 O 4 supports and Pd-loaded catalysts. The Pd/NF300 catalyst showed high activity for both Suzuki and Heck reactions even under a very low Pd using amount (0.08 mol% Pd based on aryl halide). Moreover, the catalyst could be magnetically separated, recycled, and showed a very slight reduction in catalytic activity after five cycles. A synergetic catalytic effect between the well dispersed Pd 0 and the basic mesoporous structure of magnetic supports has been proposed to understand its greatly enhanced catalytic activities.
TL;DR: By destabilizing the transition state of 2,1-insertion via steric interactions, the regioselectivity of methyl acrylate insertion into palladium–methyl and phenyl bonds can be inverted entirely to yield the opposite “regioirregular” products in stoichiometric reactions.
Abstract: In modern methods for the preparation of small molecules and polymers, the insertion of substrate carbon–carbon double bonds into metal–carbon bonds is a fundamental step of paramount importance. This issue is illustrated by Mizoroki–Heck coupling as the most prominent example in organic synthesis and also by catalytic insertion polymerization. For unsymmetric substrates H2C = CHX the regioselectivity of insertion is decisive for the nature of the product formed. Electron-deficient olefins insert selectively in a 2,1-fashion for electronic reasons. A means for controlling this regioselectivity is lacking to date. In a combined experimental and theoretical study, we now report that, by destabilizing the transition state of 2,1-insertion via steric interactions, the regioselectivity of methyl acrylate insertion into palladium–methyl and phenyl bonds can be inverted entirely to yield the opposite “regioirregular” products in stoichiometric reactions. Insights from these experiments will aid the rational design of complexes which enable a catalytic and regioirregular Mizoroki–Heck reaction of electron-deficient olefins.