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04 Jul 09:16

Reversible 1,1-hydroaluminations and C–H activation in reactions of a cyclic (alkyl)(amino) carbene with alane

Chem. Commun., 2018, 54,8407-8410
DOI: 10.1039/C8CC05013A, Communication
Levy L. Cao, Douglas W. Stephan
Varying the reaction ratio of cyclic (alkyl)(amino) carbene (cAACEt) with AlH3·NEtMe2 leads to the isolation of (cAACEtH)AlH2·NEtMe21 and (cAACEtH)2Al(μ-H)2AlH2·NEtMe22 and the first example of a monomeric dialkyl-aluminum hydride (cAACEtH)2AlH 3.
The content of this RSS Feed (c) The Royal Society of Chemistry
29 May 11:50

Room temperature catalytic carbon-hydrogen bond alumination of unactivated arenes: mechanism and selectivity

Chem. Sci., 2018, 9,5435-5440
DOI: 10.1039/C8SC02072H, Edge Article
Open Access Open Access
Creative Commons Licence&nbsp This article is licensed under a Creative Commons Attribution 3.0 Unported Licence.
Thomas N. Hooper, Marti Garcon, Andrew J. P. White, Mark R. Crimmin
We report the first catalytic methods for the transformation of C-H bonds of unactivated arenes into C-Al bonds.
The content of this RSS Feed (c) The Royal Society of Chemistry
19 Mar 11:25

Thermodynamic and kinetic hydricities of metal-free hydrides

Chem. Soc. Rev., 2018, 47,2809-2836
DOI: 10.1039/C7CS00171A, Review Article
Stefan Ilic, Abdulaziz Alherz, Charles B. Musgrave, Ksenija D. Glusac
Thermodynamic and kinetic hydricities provide useful guidelines for the design of hydride donors with desirable properties for catalytic chemical reductions.
The content of this RSS Feed (c) The Royal Society of Chemistry
08 Mar 16:07

Formation of Reactive π-Conjugated Frustrated N/B Pairs by Borane-Induced Propargyl Amine Rearrangement

by Tongdao Wang, Constantin G. Daniliuc, Christian Mück-Lichtenfeld, Gerald Kehr and Gerhard Erker

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Journal of the American Chemical Society
DOI: 10.1021/jacs.7b11958
03 Feb 06:21

Aluminum-Catalyzed Hydroboration of Alkenes

by Alessandro Bismuto, Michael J. Cowley and Stephen P. Thomas

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ACS Catalysis
DOI: 10.1021/acscatal.7b04279
15 Dec 19:07

A Route to Aluminumdiisocyanate and -diisothiocyanate from an Al(I) Precursor

by Herbert W. Roesky, Soumen Sinhababu, Subrata Kundu, Alexander Paesch, Regine Herbst-Irmer, Dietmar Stalke

LAl(X)2 complexes {L = HC[(CMe)(2,6-iPr2C6H3N)]2, X = NCO 2, NCS 3} have been synthesized and characterized. The synthetic strategy involves the reaction of LAl(I) with AgX (X = OCN, SCN). The reactions proceed under oxidative addition of the pseudohalides and elimination of silver metal. Both compounds reported herein have been characterized by NMR, IR, elemental analyses, LIFDI-MS, and single-crystal X-ray diffraction techniques. Compounds 2 and 3 are the first examples where two pseudohalide substituents are bound to aluminum(III).

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Aluminumdiisocyanate and aluminumdiisothiocyanide are synthesized through a novel route involving the reaction of aluminum(I) with silver salts.

11 Dec 19:10

Reversible Insertion of a CC Bond into Magnesium(I) Dimers: Generation of Highly Active 1,2-Dimagnesioethane Compounds

by Aaron J. Boutland, Ashlea Carroll, Carlos Alvarez Lamsfus, Andreas Stasch, Laurent Maron and Cameron Jones

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Journal of the American Chemical Society
DOI: 10.1021/jacs.7b11368
07 Dec 20:44

Tris(pentafluoroethyl)stannane: Tin Hydride Chemistry with an Electron-Deficient Stannane

by Markus Wiesemann, Mark Niemann, Johannes Klösener, Beate Neumann, Hans-Georg Stammler, Berthold Hoge

Abstract

A versatile two-step synthesis of tris(pentafluoroethyl)stannane, HSn(C2F5)3, is presented. Electron-withdrawing C2F5 groups significantly influence the polarity of the tin–hydrogen bond, which allows facile deprotonation of the compound, even in water. The utility of this electron-deficient stannane was illustrated in hydrostannylations of alkenes and alkynes, as well as in dehalogenation reactions. The remarkably high reactivity of HSn(C2F5)3 is demonstrated in fast hydrostannylations, even in the absence of activators, whereby the regioselectivity of this process turns out to be solvent dependent. It is of great advantage that in dehalogenation reactions volatile halogenotris(pentafluoroethyl)stannanes, XSn(C2F5)3 (X=I, Br), are formed that allow facile separation of the tin-containing byproducts from the reaction mixtures.

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Volatile separations: A versatile two-step synthesis of tris(pentafluoroethyl)stannane, HSn(C2F5)3, as a rare example of an electron-deficient stannane is presented. The utility of this volatile stannane is illustrated through the hydrostannylations of alkenes and alkynes, and dehalogenation reactions in the absence of activators.

05 Dec 17:58

Increasing Catalyst Efficiency in C−H Activation Catalysis

by Tobias Gensch, Michael James, Toryn Dalton, Frank Glorius

Abstract

C−H activation reactions with high catalyst turnover numbers are still very rare in the literature and 10 mol % is a common catalyst loading in this field. We offer a representative overview of efficient C−H activation catalysis to highlight this neglected aspect of catalysis development and inspire future effort towards more efficient C−H activation. Examples ranging from palladium catalysis, Cp*RhIII- and Cp*CoIII-catalysis, the C−H borylation and silylation to methane C−H activation are presented. In these reactions, up to tens of thousands of catalyst turnovers have been observed.

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Go, catalyst, go! C−H activation reactions with high catalyst turnover numbers are still very rare in the literature and 10 mol % is a common catalyst loading in this field. A representative overview of efficient C−H activation catalysis is presented here to highlight this neglected aspect of catalysis development and inspire future effort towards more efficient C−H activation.

03 Dec 22:57

Selective Single C(sp3)–F Bond Cleavage in Trifluoromethylarenes: Merging Visible-Light Catalysis with Lewis Acid Activation

by Kang Chen, Nele Berg, Ruth Gschwind and Burkhard König

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Journal of the American Chemical Society
DOI: 10.1021/jacs.7b10755
12 Nov 17:41

Redox-Active Ligand-Assisted Two-Electron Oxidative Addition to Gallium(II)

by Igor L. Fedushkin, Vladimir Dodonov, Alexandra Skatova, Vladimir Sokolov, Alexander Piskunov, Georgii Fukin

Abstract

The reaction of digallane (dpp-bian)Ga−Ga(dpp-bian) (2) (dpp-bian=1,2-bis[(2,6-diisopropylphenyl)imino]acenaphthene) with allyl chloride (AllCl) proceeded by a two-electron oxidative addition to afford paramagnetic complexes (dpp-bian)Ga(η1-All)Cl (3) and (dpp-bian)(Cl)Ga−Ga(Cl)(dpp-bian) (4). Treatment of complex 4 with pyridine induced an intramolecular redox process, which resulted in the diamagnetic complex (dpp-bian)Ga(Py)Cl (5). In reaction with allyl bromide, complex 2 gave metal- and ligand-centered addition products (dpp-bian)Ga(η1-All)Br (6) and (dpp-bian-All)(Br)Ga−Ga(Br)(dpp-bian-All) (7). The reaction of digallane 2 with Ph3SnNCO afforded (dpp-bian)Ga(SnPh3)2 (8) and (dpp-bian)(NCO)Ga−Ga(NCO)(dpp-bian) (9). Treatment of GaCl3 with (dpp-bian)Na in diethyl ether resulted in the formation of (dpp-bian)GaCl2 (10). Diorganylgallium derivatives (dpp-bian)GaR2 (R=Ph, 11; tBu, 14; Me, 15; Bn, 16) and (dpp-bian)Ga(η1-All)R (R=nBu, 12; Cp, 13) were synthesized from complexes 3, 10, Bn2GaCl, or tBu2GaCl by salt metathesis. The salt elimination reaction between (dpp-bian)GaI2 (17) and tBuLi was accompanied by reduction of both the metal and the dpp-bian ligand, which resulted in digallane 2 as the final product. Similarly, the reaction of complex 10 with MentMgCl (Ment=menthyl) proceeded with reduction of the dpp-bian ligand to give the diamagnetic complex [(dpp-bian)GaCl2][Mg2Cl3(THF)6] (18). Compounds 11, 12, 13, 15, and 16 were thermally robust, whereas compound 14 decomposed when heated at reflux in toluene to give complex (dpp-bian-tBu)GatBu2 (19). Both complexes 7 and 19 contain R-substituted dpp-bian ligand: in the former compound the allyl group was attached to the imino-carbon atom, whereas in complex 19, the tBu group was situated on the naphthalene ring. Crystal structures of complexes 3, 8, 9, 10, 13, 14, 18, and 19 were determined by single-crystal X-ray analysis. The presence of dpp-bian radical anions in 3, 6, 8, and 1016 was determined by ESR spectroscopy.

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Gallium complexes: Redox-active catalysts can substantially expand the reactivity of metal complexes, which can enable possible applications into catalysis. They are commonly incorporated into transition-metal complexes; however, this paper reports the oxidative addition of organic substrates to a gallium complex of redox-active 1,2-bis[(2,6-diisopropylphenyl)imino]acenaphthene (see scheme).

21 Oct 05:21

B(C6F5)3-Catalyzed Regioselective Deuteration of Electron-Rich Aromatic and Heteroaromatic Compounds

by Wu Li, Ming-Ming Wang, Yuya Hu and Thomas Werner

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Organic Letters
DOI: 10.1021/acs.orglett.7b02701
12 Oct 06:48

Hydroboration Catalyzed by 1,2,4,3-Triazaphospholenes

by Chieh-Hung Tien, Matt R. Adams, Michael J. Ferguson, Erin R. Johnson and Alexander W. H. Speed

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Organic Letters
DOI: 10.1021/acs.orglett.7b02695
12 Oct 06:47

Alkylideneborate zwitterions and C-C coupling by atypical diboration of electron-rich alkynes

Chem. Commun., 2017, 53,12132-12135
DOI: 10.1039/C7CC07409C, Communication
Julian Bohnke, Holger Braunschweig, Andrea Dei[German sz ligature}enberger, Theresa Dellermann, Rian D. Dewhurst, J. Oscar C. Jimenez-Halla, Stephanie Kachel, Hauke Kelch, Dominic Prieschl
The combination of electron-rich diaminoalkynes and ditopic Lewis acids diboranes(4) leads to unusual diboration reactions involving internal Lewis adduct and zwitterion formation and C-C bond formation.
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06 Oct 21:29

Metal-Free Borylation of Heteroarenes Using Ambiphilic Aminoboranes: On the Importance of Sterics in Frustrated Lewis Pair C–H Bond Activation

by Julien Légaré Lavergne, Arumugam Jayaraman, Luis C. Misal Castro, Étienne Rochette and Frédéric-Georges Fontaine

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Journal of the American Chemical Society
DOI: 10.1021/jacs.7b08143
04 Oct 20:08

Facile insertion of a cyclic alkyl(amino) carbene carbon into the B-B bond of diboron(4) reagents

Chem. Commun., 2017, 53,11694-11696
DOI: 10.1039/C7CC06302D, Communication
Antonius F. Eichhorn, Laura Kuehn, Todd B. Marder, Udo Radius
The carbene cAACMe reacts with diboron compounds via an irreversible insertion into the B-B bond.
The content of this RSS Feed (c) The Royal Society of Chemistry
27 Sep 23:35

Stereoselective Tandem Bis-Electrophile Couplings of Diborylmethane

by Stephanie A. Murray, Michael Z. Liang and Simon J. Meek

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Journal of the American Chemical Society
DOI: 10.1021/jacs.7b09309
26 Sep 22:37

New Tricks for an Old Dog: Aluminum Compounds as Catalysts in Reduction Chemistry

by Georgii I. Nikonov

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ACS Catalysis
DOI: 10.1021/acscatal.7b02460
22 Sep 02:49

Boron–Heteroatom Addition Reactions via Borylative Heterocyclization: Oxyboration, Aminoboration, and Thioboration

by Adena Issaian, Kim N. Tu and Suzanne A. Blum

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Accounts of Chemical Research
DOI: 10.1021/acs.accounts.7b00365
19 Sep 16:09

Cover Feature: Alkali Metal Cation Affinities of Anionic Main Group-Element Hydrides Across the Periodic Table (Chem. Asian J. 19/2017)

by Zakaria Boughlala, Célia Fonseca Guerra, F. Matthias Bickelhaupt
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The Cover Feature displays possible alkali cation/anionic base pairs across the periodic table. In their Full Paper, F. Matthias Bickelhaupt et al. discuss the results of an extensive exploration and detailed analyses of alkali metal cation affinities (AMCA) of archetypal anionic bases with electrophilic centers across the periodic table. AMCAs are significantly weaker and show a number of different trends if compared to the corresponding proton affinities (PAs). Bonding analyses trace the differences to the more diffuse nature and higher energy of the alkali cation ns LUMO as compared to the proton 1s LUMO. More information can be found in the Full Paper by F. Matthias Bickelhaupt et al. on page 2604 in Issue 19, 2017 (DOI:10.1002/asia.201700956).

19 Sep 06:38

Late-stage chemoselective functional-group manipulation of bioactive natural products with super-electrophilic silylium ions

by Trandon A. Bender

Nature Chemistry. doi:10.1038/nchem.2863

Authors: Trandon A. Bender, Philippa R. Payne & Michel R. Gagné

Determining the structure­–activity relationships for complex structures can be quite challenging, but it is often the method by which many natural products are optimized for use as drugs. Now, the combination of a fluoroaryl borane catalyst, a phosphine additive and a silane reducing agent enables the late-stage selective modification of complex bioactive natural products in order to provide rapid access to a wide array of structures, and therefore functions.

19 Sep 06:38

Late-stage chemoselective functional-group manipulation of bioactive natural products with super-electrophilic silylium ions

by Trandon A. Bender

Late-stage chemoselective functional-group manipulation of bioactive natural products with super-electrophilic silylium ions

Nature Chemistry, Published online: 18 September 2017; doi:10.1038/nchem.2863

Determining the structure­–activity relationships for complex structures can be quite challenging, but it is often the method by which many natural products are optimized for use as drugs. Now, the combination of a fluoroaryl borane catalyst, a phosphine additive and a silane reducing agent enables the late-stage selective modification of complex bioactive natural products in order to provide rapid access to a wide array of structures, and therefore functions.

14 Sep 19:00

Divalent Silicon-Assisted Activation of Dihydrogen in a Bis(N-heterocyclic silylene)xanthene Nickel(0) Complex for Efficient Catalytic Hydrogenation of Olefins

by Yuwen Wang, Arseni Kostenko, Shenglai Yao and Matthias Driess

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Journal of the American Chemical Society
DOI: 10.1021/jacs.7b07167
14 Sep 18:59

Synthesis, Structure, and Reactivity of a Terminal Magnesium Hydride Compound with a Carbatrane Motif, [TismPriBenz]MgH: A Multifunctional Catalyst for Hydrosilylation and Hydroboration

by Michael Rauch, Serge Ruccolo and Gerard Parkin

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Journal of the American Chemical Society
DOI: 10.1021/jacs.7b06719
22 Jun 08:19

Oxidative Cleavage of the CN Bond on Al(I)

by Terry Chu, Sergei F. Vyboishchikov, Bulat M. Gabidullin and Georgii I. Nikonov

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Journal of the American Chemical Society
DOI: 10.1021/jacs.7b04841
16 Jun 14:06

Alkynyl Moiety for Triggering 1,2-Metallate Shifts: Enantiospecific sp2–sp3 Coupling of Boronic Esters with p-Arylacetylenes

by Varinder Kumar Aggarwal

Abstract

The enantiospecific coupling of secondary and tertiary boronic esters to aromatics has been investigated. Using p-lithiated phenylacetylenes and a range of boronic esters coupling has been achieved by the addition of N-bromosuccinimide (NBS). The alkyne functionality of the intermediate boronate complex reacts with NBS triggering the 1,2-migration of the group on boron to carbon giving a dearomatized bromoallene intermediate. At this point elimination and rearomatization occurs with neopentyl boronic esters, giving the coupled products. However, using pinacol boronic esters, the boron moiety migrates to the adjacent carbon resulting in formation of ortho boron-incorporated coupled products. The synthetic utility of the boron incorporated product has been demonstrated by orthogonal transformation of both the alkyne and boronic ester functionalities.

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Find your way: The enantiospecific coupling of secondary and tertiary boronic esters to p-arylacetylenes has been achieved by the addition of N-bromosuccinimide. By tuning the steric environment around boron, the coupled product with or without boron can be targeted. The boron containing product is highly versatile as each functional group can be transformed chemoselectively.

14 Jun 12:13

Transition-Metal-Free Homologative Cross-Coupling of Aldehydes and Ketones with Geminal Bis(boron) Compounds

by Thomas C. Stephens and Graham Pattison

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Organic Letters
DOI: 10.1021/acs.orglett.7b01474
04 Jun 15:52

Noncovalent Interactions in Ir-Catalyzed C–H Activation: L-Shaped Ligand for Para-Selective Borylation of Aromatic Esters

by Md Emdadul Hoque, Ranjana Bisht, Chabush Haldar and Buddhadeb Chattopadhyay

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Journal of the American Chemical Society
DOI: 10.1021/jacs.7b04490
23 May 10:07

Deprotonation of a Seemingly Hydridic Diborane(6) to Build a B−B Bond

by Thomas Kaese, Hendrik Budy, Michael Bolte, Hans-Wolfram Lerner, Matthias Wagner

Abstract

Deprotonation of the doubly arylene-bridged diborane(6) derivative 1H2 with (Me3Si)3CLi or (Me3Si)2NK gives the B−B σ-bonded species M[1H] in essentially quantitative yields (THF, room temperature; M=Li, K, arylene=4,4′-di-tert-butyl-2,2′-biphenylylene). With nBuLi as the base, the yield of Li[1H] drops to 20 % and the 1,1-bis(9-borafluorenyl)butane Li[2H] is formed as a side product (30 %). In addition to the 1,1-butanediyl fragment, the two boron atoms of Li[2H] are linked by a μ-H bridge. In the closely related molecule Li[3H], the corresponding μ-H atom can be abstracted with (Me3Si)3CLi to afford the B−B-bonded conjugated base Li2[3] (THF, 150 °C; 15 %). Li[1H] and Li[2H] were characterized by NMR spectroscopy and X-ray crystallography.

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Fluid identity: A B−B bond was formed through the deprotonation of a doubly arylene-bridged diborane(6) derivative. The reaction shows that organoboranes are not necessarily hydridic and paves the way for new access routes to electron-precise diboranes.

21 May 15:48

Rh-Catalyzed Anti-Markovnikov Hydrocyanation of Terminal Alkynes

by Fei Ye, Junting Chen and Tobias Ritter

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Journal of the American Chemical Society
DOI: 10.1021/jacs.7b03749