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13 Oct 17:33

Kinetic or Dynamic Control on a Bifurcating Potential Energy Surface? An Experimental and DFT Study of Gold-Catalyzed Ring Expansion and Spirocyclization of 2-Propargyl-β-tetrahydrocarbolines

by Lei Zhang, Yi Wang, Zhu-Jun Yao, Shaozhong Wang and Zhi-Xiang Yu

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Journal of the American Chemical Society
DOI: 10.1021/jacs.5b05971
13 Oct 17:31

Homogeneous Gold-Catalyzed Cyclization Reactions of Alkynes with N- and S-Nucleophiles

by Wouter Debrouwer, Thomas S. A. Heugebaert, Bart I. Roman, Christian V. Stevens

Abstract

This review covers the formation of N- and S-containing heterocycles, initiated by gold-catalyzed nucleophilic attack of N- or S-nucleophiles onto alkynes. These types of nucleophiles have been somewhat overlooked as compared to their C- or O-counterparts in other reviews. In this particular work, their intramolecular gold-mediated attack onto alkynes is reviewed in depth. It is structured in such a fashion that the reader will get a clear view of which substrates react in which cyclization mode.

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06 Oct 08:47

Oxidant-Free Au(I)-Catalyzed Halide Exchange and Csp2–O Bond Forming Reactions

by Jordi Serra, Christopher J. Whiteoak, Ferran Acuña-Parés, Marc Font, Josep M. Luis, Julio Lloret-Fillol and Xavi Ribas

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Journal of the American Chemical Society
DOI: 10.1021/jacs.5b08756
05 Oct 15:45

One-Step Conversion of Methyl Ketones to Acyl Chlorides

by Florencio Zaragoza

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The Journal of Organic Chemistry
DOI: 10.1021/acs.joc.5b01707
05 Oct 15:45

Route to α-Aryl Phosphonoacetates: Useful Synthetic Precursors in the Horner–Wadsworth–Emmons Olefination

by Kelsey F. VanGelder, Melinda Wang and Marisa C. Kozlowski

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The Journal of Organic Chemistry
DOI: 10.1021/acs.joc.5b01887
05 Oct 15:42

Dinuclear planar chiral ferrocenyl gold(I) & gold(II) complexes

Chem. Commun., 2015, 51,16806-16809
DOI: 10.1039/C5CC07018J, Communication
Marta Ayerbe Garcia, Wolfgang Frey, Mark R. Ringenberg, Max Schwilk, Rene Peters
The first scalemic ferrocenyl gold(I) and gold(II) complexes have been prepared and structurally analysed by X-ray, (spectro)electrochemical and DFT studies.
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02 Oct 14:14

Stereodivergent Dual Catalytic α-Allylation of Protected α-Amino- and α-Hydroxyacetaldehydes

by Tobias Sandmeier, Simon Krautwald, Hannes F. Zipfel, Erick M. Carreira

Abstract

Fully stereodivergent dual-catalytic α-allylation of protected α-amino- and α-hydroxyacetaldehydes is achieved through iridium- and amine-catalyzed substitution of racemic allylic alcohols with chiral enamines generated in situ. The operationally simple method furnishes useful aldehyde building blocks in good yields, more than 99 % ee, and with d.r. values greater than 20:1 in some cases. Additionally, the γ,δ-unsaturated products can be further functionalized in a stereodivergent fashion with high selectivity and with preservation of stereochemical integrity at the Cα position.

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Be selective: Ir-catalyzed allylic substitution of racemic allylic alcohols with chiral enamines generated in situ enables the fully stereodivergent α-allylation of protected α-amino- and α-hydroxyacetaldehydes. The method furnishes α-N/O-substituted γ,δ-unsaturated aldehydes in good yields and with excellent enantioselectivities. Phth=phthalimide; cod=1,5-cyclooctadiene; Ts=p-toluenesulfonyl; DCE=1,2-dichloroethane.

01 Oct 16:40

Synthesis and Evaluation of 5,5′-Bitetralone-Based Chiral Phosphoric Acids

by Yazhou Wang, Wei Liu, Wenlong Ren and Yian Shi

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Organic Letters
DOI: 10.1021/acs.orglett.5b02400
29 Sep 10:26

Synthesis of 2,5-Dihydrofurans via a Gold(I)-Catalyzed Formal [4 + 1] Cycloaddition of α-Diazoesters and Propargyl Alcohols

by Jing Wang, Xinbo Yao, Tao Wang, Jie Han, Jin Zhang, Xi Zhang, Ping Wang and Zunting Zhang

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Organic Letters
DOI: 10.1021/acs.orglett.5b02663
28 Sep 16:45

[Report] Conversion of alcohols to enantiopure amines through dual-enzyme hydrogen-borrowing cascades

by Francesco G. Mutti
α-Chiral amines are key intermediates for the synthesis of a plethora of chemical compounds at industrial scale. We present a biocatalytic hydrogen-borrowing amination of primary and secondary alcohols that allows for the efficient and environmentally benign production of enantiopure amines. The method relies on a combination of two enzymes: an alcohol dehydrogenase (from Aromatoleum sp., Lactobacillus sp., or Bacillus sp.) operating in tandem with an amine dehydrogenase (engineered from Bacillus sp.) to aminate a structurally diverse range of aromatic and aliphatic alcohols, yielding up to 96% conversion and 99% enantiomeric excess. Primary alcohols were aminated with high conversion (up to 99%). This redox self-sufficient cascade possesses high atom efficiency, sourcing nitrogen from ammonium and generating water as the sole by-product. Authors: Francesco G. Mutti, Tanja Knaus, Nigel S. Scrutton, Michael Breuer, Nicholas J. Turner
28 Sep 16:39

[Report] O–H hydrogen bonding promotes H-atom transfer from α C–H bonds for C-alkylation of alcohols

by Jenna L. Jeffrey
The efficiency and selectivity of hydrogen atom transfer from organic molecules are often difficult to control in the presence of multiple potential hydrogen atom donors and acceptors. Here, we describe the mechanistic evaluation of a mode of catalytic activation that accomplishes the highly selective photoredox α-alkylation/lactonization of alcohols with methyl acrylate via a hydrogen atom transfer mechanism. Our studies indicate a particular role of tetra-n-butylammonium phosphate in enhancing the selectivity for α C–H bonds in alcohols in the presence of allylic, benzylic, α-C=O, and α-ether C–H bonds. Authors: Jenna L. Jeffrey, Jack A. Terrett, David W. C. MacMillan
28 Sep 11:23

Synthesis and Catalytic Use of Gold(I) Complexes Containing a Hemilabile Phosphanylferrocene Nitrile Donor

by Karel Škoch, Ivana Císařová, Petr Štěpnička

Abstract

Removal of the chloride ligand from [AuCl(1P)] (2) containing a P-monodentate 1′-(diphenylphosphanyl)-1-cyanoferrocene ligand (1), by using silver(I) salts affords cationic complexes of the type [Au(1)]X, which exist either as cyclic dimers [Au(1)]2X2 (3 a, X=SbF6; 3 c, X=NTf2) or linear coordination polymers [Au(1)]nXn (3 a′, X=SbF6; 3 b′, X=ClO4), depending on anion X and the isolation procedure. As demonstrated for 3 a′, the polymers can be readily cleaved by the addition of donors, such as Cl, tetrahydrothiophene (tht) or 1, giving rise to the parent compound 2, [Au(tht)(1P)][SbF6] (5 a) or [Au(1P)2][SbF6] (4 a), respectively, of which the last two compounds can also be prepared by stepwise replacement of tht in [Au(1P)2][SbF6]. The particular combination of a firmly coordinated (phosphane) and a dissociable (nitrile) donor moieties renders complexes 3/3′ attractive for catalysis because they can serve as shelf-stable precursors of coordinatively unsaturated AuI fragments, analogous to those that result from the widely used [Au(PR3)(RCN)]X catalysts. The catalytic properties of the Au-1 complexes were evaluated in model annulation reactions, such as the synthesis of 2,3-dimethylfuran from (Z)-3-methylpent-2-en-4-yn-1-ol and oxidative cyclisation of alkynes with nitriles to produce 2,5-disubstituted 1,3-oxazoles. Of the compounds tested (2, 3 a′, 3 b′, 3 a, 4 a and 5 a), the best results were consistently achieved with dimer 3 c, which has good solubility in organic solvents and only one firmly bound donor at the gold atom. This compound was advantageously used in the key steps of annuloline and rosefuran syntheses.

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Self-stabilised catalysts: Dimeric and polymeric gold(I) complex cations with 1′-(diphenylphosphanyl)-1-cyanoferrocene ligand (L) coordinated as a hemilabile P,N donor, [Au(L-κ2P,N)]+, readily undergo cleavage of the Au[BOND]CN coordination bond and can be thus advantageously used as precursors for highly catalytically active, silver-free AuI species (see figure).

28 Sep 11:12

Insights into the Gold-Catalyzed Propargyl Ester Rearrangement/Tandem Cyclization Sequence: Radical versus Gold Catalysis—Myers–Saito- versus Schmittel-Type Cyclization

by Eva Rettenmeier, Max M. Hansmann, Alexander Ahrens, Katharina Rübenacker, Tapish Saboo, Joy Massholder, Christian Meier, Matthias Rudolph, Frank Rominger, A. Stephen K. Hashmi

Abstract

A detailed study of the gold-catalyzed tandem 1,3-carboxy migration/allene–enyne cycloisomerization was undertaken. It was found that after the initial allene formation the selectivity of the reaction is strongly influenced by the polarization of the remaining alkyne. Depending on the substitution pattern of the starting diynes, either a Schmittel- or a Myers–Saito-type cyclization was triggered. The 6-endo-dig Myers–Saito-type cyclization gave access to benzo[b]fluorenes, while the Schmittel pathway (5-exo-dig) delivered benzofulvenes as final products. In special cases a yet unknown pathway was opened by the ambiphilic nature of the allene moiety. In these cases completely different products were obtained by the nucleophilic attack of the alkyne moiety onto the allene that can also act as an electrophile. Mechanistic studies revealed that diradical pathways can be ruled out for this type of tandem cyclization reactions and it is shown that both steps of the reaction cascade are catalyzed by the gold complex.

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Substitution patterns: A detailed study of the gold-catalyzed tandem 1,3-carboxy migration/allene–enyne cycloisomerization was undertaken. It was found that the selectivity of the reaction is strongly influenced by the polarization of the remaining alkyne. Depending on the substitution pattern of the starting diynes, either a Schmittel- or a Myers–Saito-type cyclization was triggered (see scheme).

28 Sep 11:06

Stereo- and Chemodivergent NHC-Promoted Functionalisation of Arylalkylketenes with Chloral

by James J. Douglas, Gwydion Churchill, Alexandra M. Z. Slawin, David J. Fox, Andrew D. Smith

Abstract

Stereo- and chemodivergent enantioselective reaction pathways are observed upon treatment of alkylarylketenes and trichloroacetaldehyde (chloral) with N-heterocyclic carbenes, giving selectively either β-lactones (up to 88:12 dr, up to 94 % ee) or α-chloroesters (up to 94 % ee). Either 2-arylsubstitution or an α-branched iPr alkyl substituent within the ketene favours the chlorination pathway, allowing chloral to be used as an electrophilic chlorinating reagent in asymmetric catalysis.

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Taming chloral two ways: Stereo- and chemodivergent enantioselective reaction pathways are observed upon treatment of alkylarylketenes and trichloroacetaldehyde (chloral) with N-heterocyclic carbenes (NHCs), giving selectively either β-lactones (up to 88:12 dr, up to 94 % ee) or α-chloroesters (up to 94 % ee). Either 2-arylsubstitution or an α-branched iPr alkyl substituent within the ketene favours the chlorination pathway (see scheme).

22 Sep 16:05

Synthesis of Chiral Pyrazoles: A 1,3-Dipolar Cycloaddition/[1,5] Sigmatropic Rearrangement with Stereoretentive Migration of a Stereogenic Group

by M. Carmen Pérez-Aguilar, Carlos Valdés

Abstract

The reactions between terminal alkynes and α-chiral tosylhydrazones lead to the obtention of chiral pyrazoles with a stereogenic group directly attached at a nitrogen atom. The cascade reaction includes decomposition of the hydrazone into a diazocompound, 1,3-dipolar cycloaddition of the diazo compound with the alkyne, and [1,5] sigmatropic rearrangement with migration of the stereogenic group. This strategy has been successfully applied to the synthesis of structurally diverse chiral pyrazoles through α-chiral tosylhydrazones, obtained from α-phenylpropionic acid, α-amino acids, and 2-methoxycyclohexanone. Notably, the stereoretention of the [1,5] sigmatropic rearrangements represent very rare examples of this stereospecific transformation.

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Maintaining a (con)figur(ation): Retention of configuration in [1,5] sigmatropic shifts are predicted by the Woodward–Hoffmann rules, but are not well-documented experimentally. Such shifts are observed in the reactions of α-chiral tosylhydrazones with terminal alkynes. The chiral pyrazole products are formed by a 1,3-dipolar cycloaddition and subsequent site-, regio-, and stereospecific [1s,5s] sigmatropic rearrangement. Ts=4-toluenesulfonyl.

22 Sep 16:04

Highly Regio-, Diastereo-, and Enantioselective Gold(I)-Catalyzed Intermolecular Annulations with N-Allenamides at the Proximal CC Bond

by Yidong Wang, Peichao Zhang, Deyun Qian, Junliang Zhang

Abstract

A highly enantioselective gold(I)-catalyzed intermolecular annulation of 2-(1-alkynyl)-2-alken-1-ones with N-allenamides is presented. The present work represents the first example of a gold-catalyzed annulation with the proximal C[DOUBLE BOND]C bond of an N-allenamide, and is distinctly different from the previously observed annulations at the distal C[DOUBLE BOND]C bond. Interestingly, both enantiomers of the products could be obtained in good yields with high regio-, diastereo-, and enantioselectivity by using either diastereomer of a binol-derived phosphoramidite as a chiral ligand.

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On the double: An unprecedented [3+2] annulation takes place with the proximal C[DOUBLE BOND]C bond of N-allenamides in the presence of a chiral gold catalyst. Both enantiomers could be obtained in good yields with high regio-, diastereo-, and enantioselectivities by using either diastereomer of a binol-derived phosphoramidite ligand. binol=1,1′-bi-2-naphthol.

22 Sep 14:08

Gold(I)-Catalyzed Addition of Silylacetylenes to Acylsilanes: Synthesis of Indanones by CH Functionalization through a Gold(I) Carbenoid

by Jairo González, Javier Santamaría, Alfredo Ballesteros

Abstract

A gold(I)-catalyzed synthesis of indanones from trimethylsilylacetylenes and acylsilanes is presented. The reaction is initiated through a synergistic acylsilane activation–gold acetylide formation and involves consecutive alkyne σ-gold(I) addition, π-activation, and 1,2-migration of a silyl group. Studies performed on the reaction mechanism allowed to establish the nature of the silyl migrating group and invoke the participation of a gold(I) carbenoid intermediate. The reaction is completed by a gold(I) C[BOND]H functionalization step.

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The elegant way: A gold(I)-catalyzed synthesis of indanones from trimethylsilylacetylenes and acylsilanes was developed. The reaction involves a synergistic acylsilane activation–gold acetylide formation and consecutive alkyne σ-gold(I) addition, π-activation, and 1,2-silyl migration. Mechanistic studies suggest the participation of a gold(I) carbenoid intermediate.

18 Sep 14:48

Mechanistic Understanding of the Divergent Cyclizations of o-Alkynylbenzaldehyde Acetals and Thioacetals Catalyzed by Metal Halides

by Yanhua Mi, Tao Zhou, Kung-Pern Wang, Daesung Lee, Yuanzhi Xia

Abstract

The mechanisms of regiodivergent cyclizations of o-alkynylbenzaldehyde acetals and thioacetals catalyzed by Pd and Pt halides are studied. DFT calculations found that both reactions are initiated by electrophilic activation of the acetylenic moiety instead of the previously proposed metal-triggered C[BOND]X (X=O, S) cleavage. Both the regioselective cyclization of the π-alkyne complex and the chemoselective [1,2]-migration in the carbenoid intermediate were determined as key steps to achieving the observed divergence. For acetal derivatives containing an internal alkyne, the 6-endo-dig cyclization is more favorable and leads to the carbenoid intermediate easily through further steps of C[BOND]X fragmentation and carbocation cyclization. Then, from the carbenoid intermediate, the [1,2]-migration of sulfur is easier than that of H, Me, and Ph; whereas, a reversed aptitude was predicted for the oxygen analogue, which is consistent with the greater ability of sulfur atoms to stabilize β-carbocations. However, for precursors containing a terminal alkyne, the 5-exo-dig pathway is preferred and only the 1,2-disubstituted indene product is seen, irrespective of the nature of the acetal; thus, a different product from that reported in the literature is predicted for benzaldehyde acetal with a terminal alkyne at the ortho position. This prediction led us to reconsider some of the reported results and hidden realities were uncovered with solid new experimental evidence.

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Where paths diverge: In-depth mechanistic understanding of the regiodivergent cyclizations of o-alkynylbenzaldehyde acetals and thioacetals catalyzed by Pd and Pt halides is achieved by combined theoretical and experimental studies (see scheme).

16 Sep 16:54

Formal Gold-to-Gold Transmetalation of an Alkynyl Group Mediated by Palladium: A Bisalkynyl Gold Complex as a Ligand to Palladium

by Alberto Toledo, Isabel Meana, Ana C. Albéniz

Abstract

The reaction of [Au(C[TRIPLE BOND]C[BOND]n-Bu)]n with [Pd(η3-allyl)Cl(PPh3)] results in a ligand and alkynyl rearrangement, and leads to the heterometallic complex [Pd(η3-allyl){Au(C[TRIPLE BOND]C[BOND]n-Bu)2}]2 (3) with an unprecedented bridging bisalkynyl–gold ligand coordinated to palladium. This is a formal gold-to-gold transmetalation that occurs through reversible alkynyl transmetalations between gold and palladium.

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Back and forth! Direct gold-to-palladium and reverse palladium-to-gold alkynyl transmetalations effectively produce a deceptively simple gold-to-gold transfer. The resulting bisalkynyl–gold complexes act as bridging ligands to palladium atoms in an unprecedented structural motive (see scheme).

25 Jun 07:51

Gold(I)-catalyzed cycloisomerization of vinylidenecyclopropane-enes via carbene or non-carbene processes

Chem. Sci., 2015, 6,5519-5525
DOI: 10.1039/C5SC01806D, Edge Article
Open Access Open Access
Creative Commons Licence&nbsp This article is licensed under a Creative Commons Attribution 3.0 Unported Licence.
De-Yao Li, Yin Wei, Ilan Marek, Xiang-Ying Tang, Min Shi
Gold catalyzed cycloisomerization of aromatic ring tethered vinylidenecyclopropane-enes provides a divergent synthetic protocol for the construction of O-containing fused heterocycles through controllable carbene or non-carbene related processes.
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25 Jun 07:49

Gold(I)-catalysed cascade reactions in the synthesis of 2,3-fused indole derivatives

Chem. Commun., 2015, 51,12384-12387
DOI: 10.1039/C5CC04606H, Communication
Ana Gimeno, Alejandra Rodriguez-Gimeno, Ana B. Cuenca, Carmen Ramirez de Arellano, Mercedes Medio-Simon, Gregorio Asensio
Unactivated alkenes and 1,3-unsubstituted indoles in gold(I)-catalysed hydroaminative/arylative cascade cyclizations.
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25 Jun 07:48

Highly Regio- and Diastereoselective Formation of Tetrasubstituted (Z)-1,2-Dihaloalkenes from the Halogenation of Trimethylsilyl Alkynes with ICl

by Kyle C. Sproul and Wesley A. Chalifoux

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Organic Letters
DOI: 10.1021/acs.orglett.5b01558
24 Jun 08:42

A Theoretical Study on the Protodeauration Step of the Gold(I)-Catalyzed Organic Reactions

by Rasool BabaAhmadi, Parisa Ghanbari, Nasir Ahmad Rajabi, A. Stephen K. Hashmi, Brian F. Yates and Alireza Ariafard

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Organometallics
DOI: 10.1021/acs.organomet.5b00219
19 Jun 09:22

An Au(I)-catalyzed rearrangement/cyclization cascade toward the synthesis of 2-substituted-1,4,5,6-tetrahydrocyclopenta[b]pyrrole

Chem. Commun., 2015, 51,12064-12067
DOI: 10.1039/C5CC03979G, Communication
Xue-Qing Mou, Zheng-Liang Xu, Shao-Hua Wang, Dao-Yong Zhu, Jie Wang, Wen Bao, Shi-Jiang Zhou, Chao Yang, Di Zhang
An Au(I)-catalyzed tandem reaction, involving a Meyer-Schuster rearrangement/1,2-migration/Paal-Knorr cyclization cascade has been successfully developed.
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19 Jun 08:49

Catalyst-Dependent Stereodivergent and Regioselective Synthesis of Indole-Fused Heterocycles through Formal Cycloadditions of Indolyl-Allenes

by Liang-Yong Mei, Yin Wei, Xiang-Ying Tang and Min Shi

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Journal of the American Chemical Society
DOI: 10.1021/jacs.5b02080
15 Jun 09:53

Gold(I)-Catalyzed 1,3-O-Transposition Reactions: Ynesulfonamides to Ynamides

by De-Yao Li, Yin Wei, Min Shi

Abstract

The gold-catalyzed 1,3-O-transposition reaction of ynesulfonamides provides a practical synthetic protocol for the synthesis of ynamides under mild conditions. This is the first 1,3-O-transposition example of ynesulfonamides in which a heteroatom is attached to the alkynyl terminal. A plausible mechanism is been proposed on the basis of 18O-labeling and control experiments as well as DFT calculation. By simple treatment, the obtained ynamides can easily be transformed into useful products.

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The gold-catalyzed 1,3-O-transposition reaction of ynesulfonamides provides a practical synthetic protocol for the synthesis of ynamides under mild conditions. This is the first 1,3-O-transposition example of ynesulfonamides in which a heteroatom is attached to the alkynyl terminal.

01 Jun 11:57

Silica-Supported Cationic Gold(I) Complexes as Heterogeneous Catalysts for Regio- and Enantioselective Lactonization Reactions

by Xing-Zhong Shu, Son C. Nguyen, Ying He, Fadekemi Oba, Qiao Zhang, Christian Canlas, Gabor A. Somorjai, A. Paul Alivisatos and F. Dean Toste

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Journal of the American Chemical Society
DOI: 10.1021/jacs.5b04294
28 May 09:00

Chiral Brønsted Acid as a True Catalyst: Asymmetric Mukaiyama Aldol and Hosomi–Sakurai Allylation Reactions

by Masahiro Sai and Hisashi Yamamoto

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Journal of the American Chemical Society
DOI: 10.1021/jacs.5b04168
07 May 16:57

Synthesis and Characterization of a Gold Vinylidene Complex Lacking π-Conjugated Heteroatoms

by Robert J. Harris, Ross A. Widenhoefer

Abstract

Hydride abstraction from the gold (disilyl)ethylacetylide complex [(P)Au{η1-C[TRIPLE BOND]CSi(Me)2CH2CH2SiMe2H}] (P=P(tBu)2o-biphenyl) with triphenylcarbenium tetrakis(pentafluorophenyl)borate at −20 °C formed the cationic gold (β,β-disilyl)vinylidene complex [(P)Au[DOUBLE BOND]C[DOUBLE BOND]CSi(Me)2CH2CH2Si(Me)2]+B(C6F5)4 with ≥90 % selectivity. 29Si NMR analysis of this complex pointed to delocalization of positive charge onto both the β-silyl groups and the (P)Au fragment. The C1 and C2 carbon atoms of the vinylidene complex underwent facile interconversion (ΔG=9.7 kcal mol−1), presumably via the gold π-disilacyclohexyne intermediate [(P)Au{η2-C[TRIPLE BOND]CSi(Me)2CH2CH2Si(Me)2}]+B(C6F5)4.

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Good as gold: Cationic gold (β,β-disilyl)vinylidene complex 1 was generated by addition of a pendant silylium ion to the C[TRIPLE BOND]C bond of a gold acetylide complex (see scheme, P=PtBu2(o-biphenyl)). The vinylidene C1 and C2 atoms of 1 undergo facile interconversion, presumably via a π-disilacyclohexyne intermediate. 29Si NMR analysis of 1 indicates delocalization of positive charge onto both the β-silyl groups and the (P)Au fragment.

07 May 14:23

The Stabilizing Effects in Gold Carbene Complexes

by Laura Nunes dos Santos Comprido, Johannes E. M. N. Klein, Gerald Knizia, Johannes Kästner, A. Stephen K. Hashmi

Abstract

Bonding and stabilizing effects in gold carbene complexes are investigated by using Kohn–Sham density functional theory (DFT) and the intrinsic bond orbital (IBO) approach. The π-stabilizing effects of organic substituents at the carbene carbon atom coordinated to the gold atom are evaluated for a series of recently isolated and characterized complexes, as well as intermediates of prototypical 1,6-enyne cyclization reactions. The results indicate that these effects are of particular importance for gold complexes especially because of the low π-backbonding contribution from the gold atom.

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Is anybody there? Intrinsic bond orbital analyses based on DFT calculations on gold carbene complexes indicate little π backbonding from gold (A) and π stabilization from organic fragments even in cyclopropyl-substituted gold carbene complex intermediates (B, C).