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Aaron M. Tondreau

Other affiliations: Momentive, ETH Zurich, Cornell University  ...read more
Bio: Aaron M. Tondreau is an academic researcher from Los Alamos National Laboratory. The author has contributed to research in topics: Hydrosilylation & Pyridine. The author has an hindex of 18, co-authored 41 publications receiving 2040 citations. Previous affiliations of Aaron M. Tondreau include Momentive & ETH Zurich.

Papers
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Journal ArticleDOI
03 Feb 2012-Science
TL;DR: It is reported that well-characterized molecular iron coordination compounds promote the selective anti-Markovnikov addition of sterically hindered, tertiary silanes to alkenes under mild conditions, showing promise for industrial application.
Abstract: Alkene hydrosilylation, the addition of a silicon hydride (Si-H) across a carbon-carbon double bond, is one of the largest-scale industrial applications of homogeneous catalysis and is used in the commercial production of numerous consumer goods. For decades, precious metals, principally compounds of platinum and rhodium, have been used as catalysts for this reaction class. Despite their widespread application, limitations such as high and volatile catalyst costs and competing side reactions have persisted. Here, we report that well-characterized molecular iron coordination compounds promote the selective anti-Markovnikov addition of sterically hindered, tertiary silanes to alkenes under mild conditions. These Earth-abundant base-metal catalysts, coordinated by optimized bis(imino)pyridine ligands, show promise for industrial application.

444 citations

Journal ArticleDOI
TL;DR: In this paper, the chemistry of enantiopure pyridine bis(oxazoline) iron compounds has been explored, and the electronic properties of this ligand class have been evaluated relative to aryl- and alkyl-substituted bis(imino)pyridines using cyclic voltammetry and CO stretching frequencies of iron dicarbonyl compounds.

197 citations

Journal ArticleDOI
TL;DR: Bis(imino)pyridine iron dinitrogen and dialkyl complexes are well-defined precatalysts for the chemo- and regioselective reduction of aldehydes and ketones, representing one of the most active iron-catalyzed carbonyl reductions reported to date.

190 citations

Journal ArticleDOI
TL;DR: In this paper, the electron transfer was used to reveal the central pnictogen atom in both cases as the main carrier of the spin density (∼60%), and that they are best described as the P3 or PAsP analogues of the elusive allyl radical dianion.
Abstract: Sodium phosphaethynolate, Na(OCP), reacts as a P− transfer reagent with the imidazolium salt [DippNHC–H][Cl] [DippNHC = 1,3-bis(2,6-diisopropylphenyl)imidazol-2-ylidene] to give the parent phosphinidene–carbene adduct, DippNHCPH, with the loss of CO. In a less atom economic reaction, the cage compound, P7(TMS)3 (TMS = SiMe3) reacts likewise with the imidazolium salt to yield DippNHCPH thereby giving two entry points into parent phosphinidene-based chemistry. From the building block DippNHCPH, the carbene-supported P3 cation [(DippNHC)2(μ-P3)][Cl] was rationally synthesized using half an equivalent of PCl3 in the presence of DABCO (1,4-diazabicyclo[2.2.2]octane). The corresponding arsenic analogue, [(DippNHC)2(μ-PAsP)][Cl], was synthesized in the same manner using AsCl3. The reduction of both [(DippNHC)2(μ-P3)][Cl] and [(DippNHC)2(μ-PAsP)][Cl] into their corresponding neutral radical species was achieved simply by reducing the compounds with an excess of magnesium. This allowed the electronic structures of the compounds to be investigated using a combination of NMR and EPR spectroscopy, X-ray crystallography, and computational studies. The findings of the investigation into (DippNHC)2(μ-P3) and (DippNHC)2(μ-PAsP) reveal the central pnictogen atom in both cases as the main carrier of the spin density (∼60%), and that they are best described as the P3 or PAsP analogues of the elusive allyl radical dianion. The phosphorus radical was also able to undergo a cycloaddition with an activated acetylene, followed by an electron transfer to give the ion pair [(DippNHC)2(μ-P3)][P3(C(COOMe))2].

173 citations

Journal ArticleDOI
28 Aug 2015-Science
TL;DR: An iron catalyst is reported that coaxes a wide variety of simple olefins into such rings without the need for photoexcitation and through rational ligand design, development of this base metal–catalyzed method expands the chemical space accessible from abundant hydrocarbon feedstocks.
Abstract: Cycloadditions, such as the [4+2] Diels-Alder reaction to form six-membered rings, are among the most powerful and widely used methods in synthetic chemistry. The analogous [2+2] alkene cycloaddition to synthesize cyclobutanes is kinetically accessible by photochemical methods, but the substrate scope and functional group tolerance are limited. Here, we report iron-catalyzed intermolecular [2+2] cycloaddition of unactivated alkenes and cross cycloaddition of alkenes and dienes as regio- and stereoselective routes to cyclobutanes. Through rational ligand design, development of this base metal-catalyzed method expands the chemical space accessible from abundant hydrocarbon feedstocks.

148 citations


Cited by
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Journal ArticleDOI
TL;DR: This Review compares classical and photocatalytic procedures for selected classes of reactions and highlights their advantages and limitations.
Abstract: Visible-light photocatalysis has evolved over the last decade into a widely used method in organic synthesis. Photocatalytic variants have been reported for many important transformations, such as cross-coupling reactions, α-amino functionalizations, cycloadditions, ATRA reactions, or fluorinations. To help chemists select photocatalytic methods for their synthesis, we compare in this Review classical and photocatalytic procedures for selected classes of reactions and highlight their advantages and limitations. In many cases, the photocatalytic reactions proceed under milder reaction conditions, typically at room temperature, and stoichiometric reagents are replaced by simple oxidants or reductants, such as air, oxygen, or amines. Does visible-light photocatalysis make a difference in organic synthesis? The prospect of shuttling electrons back and forth to substrates and intermediates or to selectively transfer energy through a visible-light-absorbing photocatalyst holds the promise to improve current procedures in radical chemistry and to open up new avenues by accessing reactive species hitherto unknown, especially by merging photocatalysis with organo- or metal catalysis.

1,211 citations

Journal ArticleDOI
TL;DR: In this paper, the authors highlight the use of non-innocent redox active ligands in catalysis and highlight four main application strategies of redox-active ligands: oxidation/reduction of the ligand to tune the electronic properties (i.e., Lewis acidity/basicity) of the metal.
Abstract: In this (tutorial overview) perspective we highlight the use of “redox non-innocent” ligands in catalysis. Two main types of reactivity in which the redox non-innocent ligand is involved can be specified: (A) The redox active ligand participates in the catalytic cycle only by accepting/donating electrons, and (B) the ligand actively participates in the formation/breaking of substrate covalent bonds. On the basis of these two types of behavior, four main application strategies of redox-active ligands in catalysis can be distinguished: The first strategy (I) involves oxidation/reduction of the ligand to tune the electronic properties (i.e., Lewis acidity/basicity) of the metal. In the second approach (II) the ligand is used as an electron reservoir. This allows multiple-electron transformations for metal complexes that are reluctant to such transformations otherwise (e.g., because the metal would need to accommodate an uncommon, high-energy oxidation state). This includes examples of (first row) transition ...

822 citations

Journal ArticleDOI
29 Nov 2013-Science
TL;DR: In this paper, the authors report convenient and stable iron oxide (Fe2O3)-based catalysts as a more earth-abundant alternative for the transformation of anilines.
Abstract: Production of anilines--key intermediates for the fine chemical, agrochemical, and pharmaceutical industries--relies on precious metal catalysts that selectively hydrogenate aryl nitro groups in the presence of other easily reducible functionalities. Herein, we report convenient and stable iron oxide (Fe2O3)-based catalysts as a more earth-abundant alternative for this transformation. Pyrolysis of iron-phenanthroline complexes on carbon furnishes a unique structure in which the active Fe2O3 particles are surrounded by a nitrogen-doped carbon layer. Highly selective hydrogenation of numerous structurally diverse nitroarenes (more than 80 examples) proceeded in good to excellent yield under industrially viable conditions.

800 citations

Journal ArticleDOI
TL;DR: This tutorial review summarizes recent successes in replacing expensive and toxic ruthenium in these catalysts with "greener" iron substitutes including my lab's recent progress using iron complexes containing readily-prepared tetradentate ligands to enlighten chemists interested in homogeneous catalysis and asymmetric synthesis.
Abstract: The conventional homogeneous catalysts for the enantioselective hydrogenation or transfer hydrogenation of ketones are based on platinum metals and, in particular, ruthenium. This method provides valuable enantiopure alcohols for the fine chemical industries. This tutorial review summarizes recent successes in replacing expensive and toxic ruthenium in these catalysts with “greener” iron substitutes including my lab’s recent progress in this area using iron complexes containing readily-prepared tetradentate ligands. It will enlighten chemists interested in homogeneous catalysis and asymmetric synthesis.

649 citations