Gold-catalyzed Addition Research Articles

Gold-Catalyzed Addition of β-Oxo Enols at Tethered Alkynes via a Non-Conia-ene Pathway: Observation of a Formal 1,3-Hydroxymethylidene Migration.

With the relay process of Ag(I)/Au(I) catalysts, a one-pot synthesis of skeletally rearranged (1-hydroxymethylidene)indene derivatives from 2-alkynylbenzaldehydes and α-diazo esters is described. This cascade sequence involves Au(I)-catalyzed 5-endo-dig attack of highly enolizable aldehydes at the tethered alkynes, leading to carbocyclizations with a formal 1,3-hydroxymethylidene transfer. On the basis of density functional theory calculations, the mechanism likely involves formation of cyclopropylgold carbenes, followed by an appealing 1,2-cyclopropane migration.

Gold-Catalyzed Addition of Propargyl Acetates to Olefins via O-Acyl Migration/Cyclopropanation Sequence: Insight into the Diastereoselective Formation of the Alkene

This article discloses a study on the well-known addition of propargyl acetates to olefins via an O-acyl migration/cyclopropanation sequence. Herein, we show that the stereochemical outcome of the olefin is strongly dependent on the gold catalyst and reaction parameters (concentration, temperature, and alkene partner equivalents); the E- and Z-isomers can be selectively formed by the judicious choice of reaction conditions.

Gold(I)-Catalyzed Selective Hydroarylation of Indoles with Haloalkynes.

A highly regio- and stereoselective synthesis of a Z-alkenyl indole via the gold-catalyzed addition of an indole to a haloalkyne was developed. In the presence of gold catalyst SIPrAuCl and cocatalyst NaBARF, a broad range of indoles react with haloalkynes to afford Z-alkenyl indoles with high selectivity at room temperature. Computational studies suggest that the hydroarylation reaction takes place via a concerted C2 addition pathway of the indole to the activated haloalkyne.

Gold-Catalyzed Asymmetric Addition of Unactivated Propargylic C–H Bonds to Aldehydes

Gold-Catalyzed Asymmetric Addition of Unactivated Propargylic C–H Bonds to Aldehydes

Gold-Catalyzed Addition of Carboxylic Acids to Alkynes and Allenes: Valuable Tools for Organic Synthesis

In this contribution, the application of gold-based catalysts in the hydrofunctionalization reactions of alkynes and allenes with carboxylic acids is comprehensively reviewed. Both intra- and intermolecular processes, leading respectively to lactones and linear unsaturated esters, are covered. In addition, cascade transformations involving the initial cycloisomerization of an alkynoic acid are also discussed.

Introducing Perylene as a New Member to the Azaborine Family.

Substitutional doping of perylene with two boron atoms at the 6b/12b positions and two oxygen or nitrogen atoms at the 1/7 positions has been achieved. The modular synthesis route developed for these bis-BO- (3) and bis-BN-perylenes (5) starts from the readily accessible borinic acid derivative of the doubly brominated 9,10-dihydro-9,10-diboraanthracene (DBA), 1,5-Br2 DBA(OH)2 . A Stille-type reaction first furnishes the alkynyl-substituted species 1,5-(RCC)2 DBA(OH)2 (2), which undergo double ring closure to afford 3 via the gold-catalyzed addition of the O-H bonds to the C≡C bonds. Treatment of 2 with MeN(SiMe3 )2 leads to aminoborane intermediates 1,5-(RCC)2 DBA(N(H)Me)2 , which can be ring-closed to give 5 in a similar manner as in the case of 3. Different substituents R (such as Me, tBuPh) can be introduced at the 2/8 positions of the perylene core. The products obtained undergo reversible reduction and are efficient blue/turquoise emitters.

Homogeneous and Nanoparticle Gold-Catalyzed Hydrothiocyanation of Haloalkynes.

The first homogeneous and heterogeneous nanoparticle gold-catalyzed addition of sulfur nucleophiles to alkynes was developed. More specifically, gold-catalyzed hydrothiocyanation of haloalkynes gave good yields and good stereoselectivity of vinyl thiocyanates. Furthermore, a sulfur-based gold catalyst (PPh3AuSCN) has shown a unique reactivity in gold-catalyzed reactions such as the cyclization of N-propargylic amides.

Gold-Catalyzed Addition of β-Ketoesters to Alkenes: Influence of Electronic and Steric Effects in the Reaction Outcome.

The gold-catalyzed intermolecular hydroalkylation of olefins with β-ketoesters represents a conceptually attractive and useful synthetic tool; however, it has been scarcely applied, remaining a challenge for chemists. The aim of the current study was to investigate the addition of these 1,3-diketo-compounds to alkenes under gold catalysis conditions, in order to establish the electronic and steric effects of the alkenyl substrates in the reaction outcome. The screening of different catalyst systems and diverse olefins enabled defining the alkenyl requirements and the best reaction conditions to efficiently achieve the coupled products.

Ligand-Accelerated Gold-Catalyzed Addition of in Situ Generated Hydrazoic Acid to Alkynes under Neat Conditions.

The direct addition of in situ generated hydrazoic acid to alkynes is realized without solvent by using a gold catalyst derived from a recently designed remotely functionalized biaryl-2-ylphosphine ligand (i.e., WangPhos). With terminal alkynes, the additions are mostly realized with 0.1 mol% catalyst loadings and at 40 °C. With more challenging internal alkynes devoid of direct EWG substitution, the one-step transformation is realized for the first time with generally high efficiency at ambient temperature.

Gold-catalyzed addition reaction between creatinine and isatin: A sustainable and green chemistry approach for the diastereoselective synthesis of 3-substituted-3-hydroxyisatins

The aldolization of various isatins with creatinine under gold catalysis in water has been developed. The reaction is operationally simple as the products can be isolated by simple filtration without requiring tedious solvent extraction and column chromatographic techniques. The generality of this methodology is showcased through the reactions of a wide range of isatin derivatives with creatinine to afford the respective aldol products in excellent yields with complete syn-selectivity. The scope of this chemistry is further extended to a tandem reaction involving isatins, creatinine and malononitrile to afford multicomponent products in excellent yields with complete anti-selectivity. The antioxidant potency of the synthesized compound was assessed by a spectrophotometric method, which revealed that three compounds containing halogen atoms (2c, 2d and 2e) were the most active compared with the standard.

ChemInform Abstract: Gold‐Catalyzed Bis(stannylation) of Propiolates.

The first example of gold-catalyzed addition of Sn–Sn bonds to alkynes is reported. A cationic gold(I) complex bearing a phosphite ligand is reported to efficiently catalyze the bis(stannylation) of propiolates with hexabutylditin under mild conditions.

Highly Stereoselective Synthesis and Hydrogenation of (Z)-1-Alkyl-2-arylvinyl Acetates: a Wide Scope Procedure for the Preparation of Chiral Homobenzylic Esters

A synthesis of (Z)-1-alkyl-2-arylvinyl acetates 3 with broad scope is reported by using two complementary methods. The first one uses a stereospecific gold-catalyzed addition of acetic acid to 1-iodo-alkynes, followed by a Suzuki coupling. By the second, 1-methyl-2-arylvinyl substrates have been obtained selectively as the Z isomers by O-acylation of enolates of methyl benzyl ketones. In addition, the asymmetric hydrogenation of enol esters 3 has been covered for the first time. Using rhodium catalysts based on chiral phosphine-phosphite ligands (P-OP), highly enantioselective hydrogenations (up to 99% ee) have been achieved for a wide range of substrates. Thus, the synthesis and enantioselective hydrogenation of 3 provides a convenient and versatile procedure for the synthesis of valuable chiral homobenzylic esters.

NMR spectroscopy studies of electronic effects and equilibrium in the organogold-to-boron transmetalation reaction and studies towards its application to the alkoxyboration addition of boron–oxygen σ bonds to alkynes

Electronic effects in the transmetalation of an aryl group from gold to boron were investigated by NMR spectroscopy. The transmetalation reaction is more facile for increasingly electrophilic boron reagents and is in equilibrium under certain conditions. Observed tetracoordinate boronate compounds suggest a two-step, associative transmetalation reaction mechanism in which the organogold complex first delivers a nucleophilic phenyl group to the empty p orbital of boron. For certain substrates, this tetracoordinate intermediate decomposes to the tricordinate, final transmetallation product, and in others this tricordinate species remains in equilibrium with a tetracoordinate anionic boron compound. Experimental and theoretical investigations into the extension of this transmetalation reaction from a mechanistic step in our previously reported intramolecular gold-catalyzed addition of boron–oxygen σ bonds across alkynes to an intermolecular variant are discussed.

ChemInform Abstract: Complexity‐Generating Hydration Reactions via Gold‐Catalyzed Addition of Boronic Acids to Alkynes

ChemInformVolume 44, Issue 43 Reviews ChemInform Abstract: Complexity-Generating Hydration Reactions via Gold-Catalyzed Addition of Boronic Acids to Alkynes Tom D. Sheppard, Tom D. Sheppard Dep. Chem., Univ. Coll., London WC1H 0AJ, UKSearch for more papers by this author Tom D. Sheppard, Tom D. Sheppard Dep. Chem., Univ. Coll., London WC1H 0AJ, UKSearch for more papers by this author First published: 07 October 2013 https://doi.org/10.1002/chin.201343256AboutPDF ToolsRequest permissionExport citationAdd to favoritesTrack citation ShareShare Give accessShare full text accessShare full-text accessPlease review our Terms and Conditions of Use and check box below to share full-text version of article.I have read and accept the Wiley Online Library Terms and Conditions of UseShareable LinkUse the link below to share a full-text version of this article with your friends and colleagues. Learn more.Copy URL Share a linkShare onFacebookTwitterLinked InRedditWechat No abstract is available for this article. Volume44, Issue43October 22, 2013 RelatedInformation

Gold-Catalyzed Addition of N-Hydroxy Heterocycles to Alkynes and Subsequent 3,3-Sigmatropic Rearrangement

Gold-catalyzed intermolecular addition of hydroxybenzotriazole derivatives to alkynes at room temperature, gives vinyl ethers 3 in high yields and with excellent regioselectivity. Unlike many other vinyl ethers, 3 can easily be purified by regular silica-gel chromatography. On heating, 3,3-sigmatropic rearrangement of 3 gives access to highly functionalized benzotriazoles. This two-step sequence represents an efficient oxygen transfer protocol which incorporates a nucleophilic oxygen atom into an alkyne group. Reaction of 3 with an electrophilic fluorinating reagent (Selectfluor) gives a fluorinated ketone regioselectively and in high yield.

Gold-Catalyzed Sequential Alkyne Activation for the Synthesis of 4,6-Disubstituted Phosphorus 2-Pyrones

Tandem gold-catalyzed addition of alkynyl phosphonic acid monoethyl esters to terminal alkynes and cyclization were developed for the synthesis of 4,6-disubstituted phosphorus 2-pyrones in one reaction vessel based on the concept of sequential alkyne activation. Alkynyl enol phosphonates were selectively obtained through the gold-catalyzed addition reaction in the presence of a catalytic amount of triethylamine. Also, gold-catalyzed cyclization of alkynyl enol phosphonates was successful in giving a variety of 4,6-disubstituted phosphorus 2-pyrones.

Complexity-generating hydration reactions via gold-catalyzed addition of boronic acids to alkynes

Boronic acids can serve as organic soluble substitutes for water molecules in the metal-catalyzed hydration of alkynes. The Au-catalyzed addition of boronic acids to alkynes provides an alternative method for enolate generation, which proceeds under exceptionally mild conditions. The resulting enolates can be trapped by aldehydes present in the reaction mixture, giving aldol products that can be isolated as cyclic borate esters. These compounds are versatile synthetic intermediates that can be elaborated into a variety of products by transformation of the boron moiety. The Au-catalyzed reaction of boronic acids with propargylic alcohols results in efficient Meyer–Schuster rearrangement to the corresponding enones. The rearrangement of tertiary alcohols gives (E)-enones with moderate to good selectivity, and the addition of a boronic acid to the reaction appears to enhance the level of geometrical control. The rearrangement of primary alcohols to terminal enones also occurs readily in the presence of catalytic Au(I) and a boronic acid, and the resulting terminal enones can be reacted with nucleophiles in one-pot procedures to give a variety of β-substituted ketones.

Gold(I)-Catalyzed Regioselective Inter-/Intramolecular Addition Cascade of Di- and Triynes for Direct Construction of Substituted Naphthalenes

The gold-catalyzed cascade intermolecular addition-intramolecular carbocyclization reaction of dialkynylbenzenes was developed. In this reaction, regioselective addition of an external nucleophile toward the terminal alkyne and subsequent 6-endo-dig cyclization proceeded to give the 1,3-disubstituted naphthalenes in good yields. The direct synthesis of disubstituted chrysenes via a gold-catalyzed addition and double cyclization cascade using a triyne-type substrate was also achieved.

Au-catalyzed synthesis of 2-alkylindoles from N-arylhydroxylamines and terminal alkynes.

The first gold-catalyzed addition of N-arylhydroxylamines to aliphatic terminal alkynes is developed to access O-alkenyl-N-arylhydroxylamines, which undergo facile in situ sequential 3,3-rearrangements and cyclodehydrations to afford 2-alkylindoles with regiospecificity and under exceptionally mild reaction conditions.

An Alternative Approach to Aldol Reactions: Gold-Catalyzed Formation of Boron Enolates from Alkynes

A new method for enolate generation via the gold-catalyzed addition of boronic acids to alkynes is reported. The formation of boron enolates from readily accessible ortho-alkynylbenzeneboronic acids proceeds rapidly with 2 mol % PPh(3)AuNTf(2) at ambient temperature. The enolates undergo aldol reaction with an aldehyde present in the reaction mixture to give cyclic boronate esters, which can be subsequently transformed into phenols, biaryls, or dihydrobenzofurans via oxidation, Suzuki-Miyaura, or intramolecular Chan-Lam coupling, respectively. A combined gold/boronic acid catalyzed aldol condensation reaction of an alkynyl aldehyde was also successfully achieved.