Transition metal-catalyzed addition of C-, N- and O-nucleophiles to unactivated C–C multiple bonds
About: This article is published in Tetrahedron.The article was published on 2012-09-30. It has received 131 citations till now. The article focuses on the topics: Triphos & Xantphos.
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775 citations
TL;DR: This critical review clearly indicates that silver catalysis provides a significant impetus to the rapid evolution of alkyne-based organic reactions, such as alkynylation, hydrofunctionalization, cycloaddition, cycloisomerization, and cascade reactions.
Abstract: Silver is a less expensive noble metal. Superior alkynophilicity due to π-coordination with the carbon-carbon triple bond makes silver salts ideal catalysts for alkyne-based organic reactions. This review highlights the progress in alkyne chemistry via silver catalysis primarily over the past five years (ca. 2010-2014). The discussion is developed in terms of the bond type formed with the acetylenic carbon (i.e., C-C, C-N, C-O, C-Halo, C-P and C-B). Compared with other coinage metals such as Au and Cu, silver catalysis is frequently observed to be unique. This critical review clearly indicates that silver catalysis provides a significant impetus to the rapid evolution of alkyne-based organic reactions, such as alkynylation, hydrofunctionalization, cycloaddition, cycloisomerization, and cascade reactions.
346 citations
TL;DR: The recent uses of B(C6F5)3 in borylation reactions are shown while also focusing on current advances in novel borane and borocation usage that eclipses that of the stalwart B( C6F 5)3.
Abstract: As main-group chemistry, in particular boron chemistry, has expanded and developed over the past 20 years, one reagent has risen to prominence as well. Tris(pentafluorophenyl)borane, B(C6F5)3 (commonly known as BCF), has demonstrated extensive applications in a wide variety of reactions, including borylation, hydrogenation, hydrosilylation, frustrated Lewis pair (FLP) chemistry, Lewis acid catalysis, and more. The high Lewis acidity of B(C6F5)3 is derived from the electronic effects of its three C6F5 rings, rendering it a versatile reagent for a great number of reactions. In addition, the steric bulk of these rings also allows it to function as the Lewis acid in a FLP, granting this reagent yet another synthetically useful application. However, as main-group chemistry continues to evolve as a field, new reagents are required that go beyond BCF, increasing not only the range of reactions available but also the breadth of compounds attainable. Great strides have already been made in order to accomplish this...
158 citations
TL;DR: This review will highlight the reactions with these two metals, silver and platinum, when oxygen or nitrogen nucleophiles are employed, and describes the intramolecular and intermolecular reactions with platinum.
Abstract: Transition-metal catalysed nucleophile addition to allenes is a very powerful tool for the synthesis of functionalised molecules containing heteroatoms, heterocycles in the intramolecular version, or allyl derivatives in the intermolecular version The reaction has been explored with a wide variety of metals, silver being one of the most effective Although platinum has somehow been less explored, different reactivities have been observed with this metal, showing the great potential and versatility of this methodology This review will highlight the reactions with these two metals, silver and platinum, when oxygen or nitrogen nucleophiles are employed Although most of the examples describe the intramolecular version, some intermolecular reactions with platinum have been described, and will also be covered
157 citations
TL;DR: In this article, a review of the progress made in metal-mediated and metal-catalysed organic reactions performed in a new family of inexpensive, greener and biorenewable eutectic mixtures, the so-called deep eco-vents (DESs), as environmentally friendly reaction media is presented.
Abstract: This microreview is intended to cover the progress made in metal-mediated and metal-catalysed organic reactions performed in a new family of inexpensive, greener and biorenewable eutectic mixtures, the so-called Deep Eutectic Solvents (DESs), as environmentally friendly reaction media. This ambitious research is focused on studies of particular interest in organometallic chemistry, in search of synthetic strategies able to optimise the overall process in an eco-friendly manner. This microreview aims to provide an overview of the application of DESs in the fields of: (i) Ru- and Au-catalysed isomerisation and cycloisomerisation of organic substrates, (ii) Cu-catalysed click chemistry and C–C bond-formation reactions, (iii) Pd-catalysed cross-coupling processes and Tsuji–Trost reactions, (iv) Rh-catalysed hydrogenation and hydroformylation of alkenes, (v) addition of RMgX and RLi compounds to ketones, and (vi) regioselective ortho- and lateral lithiation of aryltetrahydrofurans.
157 citations
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TL;DR: Important vinylgold intermediates, the transmetalation from gold to other transition metals, the development of new ligands for gold catalysis, and significant contributions from computational chemistry are other crucial points for the field highlighted here.
Abstract: Although homogeneous gold catalysis was known previously, an exponential growth was only induced 12 years ago. The key findings which induce that rise of the field are discussed. This includes early reactions of allenes and furanynes and intermediates of these conversions as well as hydroarylation reactions. Other substrate types addressed are alkynyl epoxides and N-propargyl carboxamides. Important vinylgold intermediates, the transmetalation from gold to other transition metals, the development of new ligands for gold catalysis, and significant contributions from computational chemistry are other crucial points for the field highlighted here.
2,792 citations
TL;DR: The ability of platinum and gold catalysts to effect powerful atom-economic transformations has led to a marked increase in their utilization and the application of platinum- and gold-catalyzed transformations in natural product synthesis is discussed.
Abstract: The ability of platinum and gold catalysts to effect powerful atom-economic transformations has led to a marked increase in their utilization. The quite remarkable correlation of their catalytic behavior with the available structural data, coordination chemistry, and organometallic reactivity patterns, including relativistic effects, allows the underlying principles of catalytic carbophilic activation by π acids to be formulated. The spectrum of reactivity extends beyond their utility as catalytic and benign alternatives to conventional stoichiometric π acids. The resulting reactivity profile allows this entire field of catalysis to be rationalized, and brings together the apparently disparate electrophilic metal carbene and nonclassical carbocation explanations. The advances in coupling, cycloisomerization, and structural reorganization—from the design of new transformations to the improvement to known reactions—are highlighted in this Review. The application of platinum- and gold-catalyzed transformations in natural product synthesis is also discussed.
1,938 citations
TL;DR: The ways in which selectivity can be controlled in homogeneous Au catalysis are enumerated, in the hope that lessons to guide catalyst selection and the design of new catalysts may be distilled from a thorough evaluation of ligand, counterion, and oxidation state effects as they influence chemo-, regio-, and stereoselectivity in homogeneity AuCatalysis.
Abstract: 1.1. Context and Meta-Review
Despite the ubiquity of metallic gold (Au) in popular culture, its deployment in homogeneous catalysis has only recently undergone widespread investigation. In the past decade, and especially since 2004, great progress has been made in developing efficient and selective Au-catalyzed transformations, as evidenced by the prodigious number of reviews available on various aspects of this growing field. Hashmi has written a series of comprehensive reviews outlining the progression of Au-catalyzed reaction development,1 and a number of more focused reviews provide further insight into particular aspects of Au catalysis. A brief meta-review of the available range of perspectives published on Au catalysis helps to put this Chemical Reviews article in context.
The vast majority of reactions developed with homogeneous Au catalysts have exploited the propensity of Au to activate carbon-carbon π-bonds as electrophiles. Gold has come to be regarded as an exceedingly mild, relatively carbophilic Lewis acid, and the broad array of newly developed reactions proceeding by activation of unsaturated carbon-carbon bonds has been expertly reviewed.2
Further reviews and highlights on Au catalysis focus on particular classes of synthetic reactions. An excellent comprehensive review of Au-catalyzed enyne cycloisomerizations is available.3 Even more focused highlights on hydroarylation of alkynes,4 hydroamination of C-C multiple bonds,5 and reactions of oxo-alkynes6 and propargylic esters7 provide valuable perspectives on progress and future directions in the development of homogeneous Au catalysis.
Most of the reviews on Au catalysis emphasize broad or specific advances in synthetic utility. Recently, we have invoked relativistic effects to provide a framework for understanding the observed reactivity of Au catalysts, in order to complement empirical advancements.8 In this Chemical Reviews article, we attempt to enumerate the ways in which selectivity can be controlled in homogeneous Au catalysis. It is our hope that lessons to guide catalyst selection and the design of new catalysts may be distilled from a thorough evaluation of ligand, counterion, and oxidation state effects as they influence chemo-, regio-, and stereoselectivity in homogeneous Au catalysis.
1,783 citations
TL;DR: The proposed involvement of cyclopropyl metal carbenes of type 4 in the electrophilic activation of enynes by transition metals was first substantiated in reactions catalyzed by Pd(II), in which the initially formed cycloprostyl palladiumCarbenes undergo [4 + 2] cycloaddition with the double bond of the conjugate enyne.
Abstract: Gold salts and complexes have emerged in the past few years as the most powerful catalysts for electrophilic activation of alkynes toward a variety of nucleophiles under homogeneous conditions. In a simplified form, nucleophilic attack on the [AuL]-activated alkyne proceeds via π complexes 1 to give trans-alkenyl gold complexes of type 2 as intermediates (Scheme 1). This type of coordination is also a common theme in gold-catalyzed cycloisomerizations of enynes, in which the alkene function acts as the nucleophile. In the reaction of enynes with complexes of other transition metals, an Alder-ene cycloisomerization can take place by simultaneous coordination of the alkyne and the alkene to the metal followed by an oxidative cyclometalation. In contrast, this process does not occur for gold(I) since oxidative addition processes are not facile for this metal. 6 In addition, the [AuL] fragment, which is isolobal to H and HgL, adopts a linear coordination and binds to either the alkene or the alkyne. Thus, cycloisomerizations of enynes catalyzed by gold proceed by an initial coordination of the metal to the alkyne, and as illustrated in Scheme 2, the resulting complex 3 reacts with the alkene by either the 5-exo-dig or 6-endo-dig pathway to form the exoor endocyclopropyl gold carbene 4 or 5, respectively, as has been established with other electrophilic transition-metal complexes or halides MXn as catalysts. The proposed involvement of cyclopropyl metal carbenes of type 4 in the electrophilic activation of enynes by transition metals was first substantiated in reactions catalyzed by Pd(II), in which the initially formed cyclopropyl palladium carbenes undergo [4 + 2] cycloaddition with the double bond of the conjugate enyne. Strong evidence for the existence of cyclopropyl metal carbenes as intermediates was also obtained in the reaction of enynes bearing additional double bonds at the alkenyl chain with Ru(II) and Pt(II) catalysts. In these reactions, the cyclopropyl metal carbenes are trapped intramolecularly by the terminal alkene to give tetracycles containing two cyclopropanes. Gold(I) complexes usually surpass the reactivity shown by Pt(II) and other electrophilic metal salts and complexes for the activation of enynes. They are highly reactive yet uniquely selective Lewis acids that have a high affinity for π bonds. This high π-acidity is linked to relativistic effects, which reach a maximum in the periodic table with gold. However, on occasion, the stronger Lewis acidity of gold complexes can be detrimental in terms of selectivity and because of their low tolerance to certain functional groups. In these instances, the less-strongly Lewis acidic Pt(II) complexes could be the catalysts of choice. * To whom correspondence should be addressed. E-mail: aechavarren@ iciq.es. † Additional affiliation: Departamento de Quı́mica Orgánica, Universidad Autónoma de Madrid, Cantoblanco, 28049 Madrid, Spain. Scheme 1 Chem. Rev. 2008, 108, 3326–3350 3326
1,728 citations
TL;DR: Thanks to gold-based catalysts, various organic transformations have been accessible under facile conditions with both high yields and chemoselectivity.
Abstract: Thanks to its unusual stability, metallic gold has been used for thousands of years in jewelry, currency, chinaware, and so forth. However, gold had not become the chemists’ “precious metal” until very recently. In the past few years, reports on gold-catalyzed organic transformations have increased substantially. Thanks to gold-based catalysts, various organic transformations have been accessible under facile conditions with both high yields and chemoselectivity.
1,698 citations