Two years have now passed since the publication of the first Thematic Series on gold catalysis for organic synthesis in this journal. In the intervening time, the pace of progress and discovery in the field has continued unabated. Many of these advancements are exemplified in the more than twenty contributions that have been collected in this second Thematic Series. The articles demonstrate the power of gold catalysis for the construction of complex structures, including the development of tandem processes, the expedient synthesis of heterocyclic structures, and applications to the synthesis of complex natural products. The field has also witnessed growth through the discovery of other modes of reactivity. For example, gold-catalyzed cycloaddition reactions, enantioselective catalysis, or oxidative transformations catalyzed by gold complexes have featured prominently.
Graphical Abstract
Scheme 1: Preparation of allenic carbamates 2a–j. Reagents and conditions: (i) Propargylamine, MgSO4, CH2Cl2,...
Scheme 2: Controlled oxycyclization reactions of allenic carbamates 2 to 1,3-oxazinan-2-ones 3 and 1,3-oxazin...
Scheme 3: Possible explanation for the gold-catalyzed isomerization reaction of 1,3-oxazinan-2-one 3a into 1,...
Scheme 4: Mechanistic explanation for the gold-catalyzed oxycyclization reactions of allenic carbamates 2 int...
Figure 1: Computed reaction profile for the reaction of AuPMe3+ and 1M. Numbers indicate the corresponding PC...
Graphical Abstract
Figure 1: The X-ray structure of 3l.
Figure 2: The X-ray structure of 3n.
Scheme 1: Proposed mechanism for the hydroamination of allenes.
Graphical Abstract
Scheme 1: Sketch illustrating preparation of the Au@HS-CNC catalyst.
Figure 1: Au4f and S2p XPS spectra of the Au@HS-CNC (4.4 mol %) catalyst.
Figure 2: TEM pictures of the HS-NCC and Au@HS-CNC (4.4 mol %) catalyst (scale bar: 5 nm).
Figure 3: Thermogravimetric behavior of the Au@HS-CNC (4.4 mol %) catalyst (A) and CNC (B).
Figure 4: FT-IR spectra of CNC, HS-CNC, and Au@HS-CNC (4.4 mol %) catalyst.
Figure 5: Solid-state 13C NMR spectra of the CNC and Au@HS-CNC (4.4 mol %) catalyst.
Figure 6: Recycling test of Au@HS-CNC (4.4 mol %) catalyst for the three-component coupling of formaldehyde, ...
Graphical Abstract
Figure 1: Donor- and acceptor-substituted alkynes for Au-catalyzed intermolecular reactions.
Scheme 1: Proposed mechanism of the [3,3]- and [1,3]-rearrangement.
Scheme 2: Experiments to investigate the reaction mechanism.
Graphical Abstract
Scheme 1: Reported cascade reactions on allenyl acetals.
Scheme 2: Gold-catalyzed cyclization of deuterated d1-1a.
Scheme 3: A plausible reaction mechanism.
Scheme 4: The reaction of propargyl acetate 5a.
Graphical Abstract
Figure 1: Benzofurans in bioactive compounds and materials.
Scheme 1: Zinc–gold catalyzed C2-alkynylation of benzofurans.
Scheme 2: Scope of the reaction.
Scheme 3: Alkynylation of 7-methoxybenzofuran (7j) [31].
Scheme 4: Alkynylation of 8-methoxypsoralen (2).
Graphical Abstract
Scheme 1: Gold(I) or gold(III)-catalyzed furan syntheses with or without nucleophiles.
Scheme 2: Copper(I)-catalyzed 1,2-migration/cycloisomerization of γ-acyloxyalkynyl ketones.
Scheme 3: Mechanistic hypothesis for gold(I)-catalyzed conversion of γ-acyloxyalkynyl ketones into furans.
Graphical Abstract
Scheme 1: Previous work on direct allylic etherification of allylic alcohols.
Figure 1: Initial side product with TMHQ.
Scheme 2: Proposed pathway.
Scheme 3: Control reactions.
Scheme 4: Reaction of 21 with added Brønsted acid co-catalyst.
Scheme 5: Suggested mechanism.
Graphical Abstract
Scheme 1: Generation of α-oxo gold carbenes via intermolecular oxidation of alkynes: a non-diazo approach.
Scheme 2: Gold-catalyzed regioselective oxidation of a sterically biased internal alkyne.
Scheme 3: Gold-catalyzed oxidation of the propargylic acetate 4a and the mechanistic rationale.
Scheme 4: A drastically different outcome by using diphenyl sulfoxide as the oxidant.
Figure 1: The impact of ligands on the ratio of 5a-OAc and 5a-H in the gold-catalyzed oxidation of 4a (reacti...
Figure 2: Natural charges at and the 13C chemical shifts of the alkynyl carbons in 4a.
Graphical Abstract
Figure 1: Structure of furanomycin and its carba- and aza-anolgue.
Scheme 1: Gold-catalyzed cycloisomerization of α-functionalized allenes.
Scheme 2: Synthesis of propargylic electrophiles 5.
Scheme 3: Synthesis of α-hydroxyallenes 7 and α-aminoallenes 8.
Scheme 4: Synthesis of azafuranomycin analog 13a.
Scheme 5: Synthesis of (αS,2R)-(2,5-dihydro-1H-pyrrol-2-yl)glycine (22).
Graphical Abstract
Scheme 1: Gold-catalyzed reactions of oxabicyclic alkenes with electron-deficient terminal alkynes.
Figure 1: Gold complexes used in this reaction.
Scheme 2: The reaction with terminal alkyne 2i as a substrate.
Scheme 3: The reaction with naphthalen-1-ol (5) as a substrate.
Scheme 4: The proposed mechanism for Au(I)-catalyzed reaction.
Graphical Abstract
Scheme 1: Microwave assisted synthesis of arylgold compounds.
Figure 1: Synthesis of arylgold compoundsa,b. aChlorogold precursor (0.32–0.37 mmol), 2 equiv arylboronic aci...
Figure 2: Hydrophenoxylation of alkynesa,b. aAlkyne (0.28 mmol), phenol (0.56 mmol), 130 °C, 20 min, no solve...
Scheme 2: Regioselectivity of the addition reaction using arylgold precatalysts. Alkyne (0.28 mmol), phenol (...
Graphical Abstract
Scheme 1: Previously reported approach from β-aminoynones for the synthesis of pyridones.
Scheme 2: Retrosynthetic analysis of (−)-epimyrtine.
Scheme 3: Synthesis of (−)-epimyrtine.
Graphical Abstract
Scheme 1: Synthesis of 3-halo-2H-chromenes.
Figure 1: X-ray molecular structure of 2f.
Scheme 2: Gram-scale synthesis of 2f.
Scheme 3: Retaining propargylic chirality.
Scheme 4: Mechanistic basis postulated for the synthesis of 2.
Graphical Abstract
Scheme 1: Gold-catalyzed synthesis of a disaccharide.
Scheme 2: Mechanistic rationale for the cleavage of the interglycosidic linkage.
Scheme 3: C-6 Benzyl ether hydrolysis and synthesis of a glycerol mannoside.
Scheme 4: Armed–disarmed effect in Ech-glycosides during gold-catalyzed reactions.
Scheme 5: Gold-catalyzed glycosidation at ambient temperature for the synthesis of trimannoside 25.
Scheme 6: Gold-catalyzed glycosidation at ambient temperature for the synthesis of higher saccharides.
Scheme 7: Gold-catalyzed glycosidation for synthesis of higher saccharides.
Graphical Abstract
Scheme 1: Straightforward synthesis of organogold complexes via deprotonation reactions, using 1.
Scheme 2: Scope of the reaction between 1 and several (hetero)aromatic amines. Reaction conditions: 1 (1 equi...
Figure 1: X-ray crystal structures of complexes 2, 3, 7, 8, 10, 11 and 12. Hydrogen atoms are omitted for cla...
Figure 2: Selected examples of gold–NHC amide complexes under UV light (λ = 366 nm).
Figure 3: Excitation (blue) and emission (pink) data for complex 3, bearing a 2-pyridine ligand (see inset).
Figure 4: (a) LUMO, (b) HOMO and (c) HOMO-1 of complex 3.
Graphical Abstract
Figure 1: Monodentate chiral NHC gold catalysts in recent years.
Scheme 1: Synthesis of compound 9.
Scheme 2: Synthesis of N-heterocyclic carbene precursor.
Scheme 3: Synthesis of benzimidazolium salt (S)-14.
Scheme 4: Synthesis of carbene Au complexes.
Figure 2: The crystal data of gold complex (S)-15a was deposited in the CCDC with the number 883917. Empirica...
Figure 3: The crystal data of gold complex (S)-15b was deposited in the CCDC with the number 883916. Empirica...
Scheme 5: Rotamers of 1a and 1b by DFT calculation reported by Slaughter’s group.
Scheme 6: The synthesis of P–Au complexes.
Figure 4: The crystal data of gold complex (S)-18 was deposited in the CCDC with the number 920617. Empirical...
Figure 5: The crystal data of gold complex (S)-22 was deposited in the CCDC with the number 928664. Empirical...
Graphical Abstract
Scheme 1: Gold(I)-catalyzed reactions of 1,6-enynes.
Scheme 2: Cyclization of o-(alkynyl)-(3-methylbut-2-enyl)benzenes 1. Previous work and proposed pathways.
Scheme 3: Synthesis of o-(alkynyl)-(3-methylbut-2-enyl)benzenes 1.
Scheme 4: Gold(I)-catalyzed cycloisomerization of 1a.
Scheme 5: Initial experiments and proof of concept.
Scheme 6: Gold(I)-catalyzed hydroxycyclization of enynes 1m,n.
Scheme 7: Gold(I)-catalyzed methoxycyclization of selected 1,6-enynes 1 [45].
Scheme 8: Labelling experiment and proposed mechanism.
Graphical Abstract
Figure 1: Gold-promoted 1,2-acyloxy migration on propargylic systems.
Scheme 1: Gold-catalyzed enantioselective intermolecular cyclopropanation.
Scheme 2: Gold-catalyzed enantioselective intramolecular cyclopropanation.
Scheme 3: Gold-catalyzed cyclohepta-annulation cascade.
Scheme 4: Application to the formal synthesis of frondosin A.
Scheme 5: Gold(I)-catalyzed enantioselective cyclopropenation of alkynes.
Scheme 6: Enantioselective cyclopropanation of diazooxindoles.
Figure 2: Proposed structures for gold-activated allene complexes.
Scheme 7: Gold-catalyzed enantioselective [2 + 2] cycloadditions of allenenes.
Scheme 8: Gold-catalyzed allenediene [4 + 3] and [4 + 2] cycloadditions.
Scheme 9: Gold-catalyzed enantioselective [4 + 2] cycloadditions of allenedienes.
Scheme 10: Gold-catalyzed enantioselective [4 + 3] cycloadditions of allenedienes.
Scheme 11: Gold-catalyzed enantioselective [4 + 2] cycloadditions of allenamides.
Scheme 12: Enantioselective [2 + 2] cycloadditions of allenamides.
Scheme 13: Mechanistic rational for the gold-catalyzed [2 + 2] cycloadditions.
Scheme 14: Enantioselective cascade cycloadditions between allenamides and oxoalkenes.
Scheme 15: Enantioselective [3 + 2] cycloadditions of nitrones and allenamides.
Scheme 16: Enantioselective formal [4 + 3] cycloadditions leading to 1,2-oxazepane derivatives.
Scheme 17: Enantioselective gold(I)-catalyzed 1,3-dipolar [3 + 3] cycloaddition between 2-(1-alkynyl)-2-alken-...
Scheme 18: Enantioselective [4 + 3] cycloaddition leading to 5,7-fused bicyclic furo[3,4-d][1,2]oxazepines.
Graphical Abstract
Figure 1: Chiral gold(I) complexes employed in 1,3-DC involving azomethine ylides.
Scheme 1: 1,3-DC of azlactone 5a and NPM.
Scheme 2: General 1,3-DC between azlactones 5 with maleimides.
Scheme 3: Formation of the amide 8aa.
Figure 2: Positive non-linear effects (NLE) observed in 1,3-DC of azlactone 7aa and NPM.
Figure 3: Main geometrical features and relative Gibbs free energies (in kcal mol−1 at 298 K) of complexes [(S...
Figure 4: Main geometrical features and relative Gibbs free energies (in kcal mol−1) of the less energetic tr...
Scheme 4: Reaction Gibbs free energy associated with the 1,3-DC of 5aa and NPM catalyzed by (Sa)-Binap gold d...
Scheme 5: ΔG calculation for the recovery of the catalytic active species.
Scheme 6: 1,3-DC of azlactone 10 and tert-butyl acrylate.
Figure 5: (A) Schematic representation of the model gold(I) ylides. (B) HOMO of the ylides and expansion orbi...
Figure 6: Main geometrical features and relative Gibbs free energies (in kcal mol−1 at 298 K) of complexes [{(...
Figure 7: Main geometrical features and relative Gibbs free energies (in kcal mol−1) of the less energetic tr...
Scheme 7: Reduction of heterocycle 7aa under different conditions.
Scheme 8: Double 1,3-DC to give polycycle 15.
Scheme 9: Reaction between 7aa and nitrostyrene.
Graphical Abstract
Scheme 1: Intermolecular O-addition to alkynes: challenge and opportunity.
Scheme 2: Acid as the critical additive for optimal performance.
Scheme 3: Reactions of internal alkyne and other O-nucleophiles. Isolated yields are given in paranthesis. aA...
Graphical Abstract
Figure 1: Elementary steps in the gold-catalyzed nucleophilic addition to olefins.
Figure 2: Different approaches for the gold-catalyzed manipulation of inactivated alkenes.
Figure 3: Computed mechanistic cycle for the gold-catalyzed alkoxylation of ethylene with PhOH.
Scheme 1: [Au(I)]-catalyzed addition of phenols and carboxylic acids to alkenes.
Scheme 2: [Au(III)] catalyzed annulations of phenols and naphthols with dienes.
Scheme 3: [Au(III)]-catalyzed addition of aliphatic alcohols to alkenes.
Scheme 4: [Au(III)]-catalyzed carboalkoxylation of alkenes with dimethyl acetals 6.
Figure 4: Postulated mechanism for the [Au(I)]-catalyzed hydroamination of olefins.
Scheme 5: Isolation and reactivity of alkyl gold intermediates in the intramolecular hydroamination of alkene...
Scheme 6: [Au(I)]-catalyzed intermolecular hydroamination of dienes.
Scheme 7: Intramolecular [Au(I)]-catalyzed hydroamination of alkenes with carbamates.
Scheme 8: [Au(I)]-catalyzed inter- as well as intramolecular addition of sulfonamides to isolated alkenes.
Scheme 9: Intramolecular hydroamination of N-alkenylureas catalyzed by gold(I) carbene complex.
Scheme 10: Enantioselective hydroamination of alkenyl ureas with biphenyl tropos ligand and chiral silver phos...
Scheme 11: Intramolecular [Au(I)]-catalyzed hydroamination of N-allyl-N’-aryl ureas. (PNP = pNO2-C6H4, PMP = p...
Scheme 12: [Au(I)]-catalyzed hydroamination of alkenes with ammonium salts.
Scheme 13: Enantioselective [Au(I)]-catalyzed intermolecular hydroamination of alkenes with cyclic ureas.
Scheme 14: Mechanistic proposal for the cooperative [Au(I)]/menthol catalysis for the enantioselective intramo...
Scheme 15: [Au(III)]-catalyzed addition of 1,3-diketones to alkenes.
Scheme 16: [Au(I)]-catalyzed intramolecular addition of β-keto amides to alkenes.
Scheme 17: Intermolecular [Au(I)]-catalyzed addition of indoles to alkenes.
Scheme 18: Intermolecular [Au(III)]-catalyzed hydroarylation of alkenes with benzene derivatives and thiophene....
Scheme 19: a) Intramolecular [Au(III)]-catalyzed hydroarylation of alkenes. b) A SEAr-type mechanism was hypot...
Scheme 20: Intramolecular [Au(I)]-catalyzed hydroalkylation of alkenes with simple ketones.
Scheme 21: Proposed reaction mechanism for the intramolecular [Au(I)]-catalyzed hydroalkylation of alkenes wit...
Scheme 22: Tandem Michael addition/hydroalkylation catalyzed by [Au(I)] and [Ag(I)] salts.
Scheme 23: Intramolecular [Au(I)]-catalyzed tandem migration/[2 + 2] cycloaddition of 1,7-enyne benzoates.
Scheme 24: Intramolecular [Au(I)]-catalyzed cyclopropanation of alkenes.
Scheme 25: Stereospecificity in [Au(I)]-catalyzed hydroalkoxylation of allylic alcohols.
Scheme 26: Mechanistic investigation on the intramolecular [Au(I)]-catalyzed hydroalkoxylation of allylic alco...
Scheme 27: Mechanistic investigation on the intramolecular enantioselective [Au(I)]-catalyzed alkylation of in...
Scheme 28: Synthesis of (+)-isoaltholactone via stereospecific intramolecular [Au(I)]-catalyzed alkoxylation o...
Scheme 29: Intramolecular enantioselective dehydrative amination of allylic alcohols catalyzed by chiral [Au(I...
Scheme 30: Enantioselective intramolecular hydroalkylation of allylic alcohols with aldehydes catalyzed by 20c...
Scheme 31: Gold-catalyzed intramolecular diamination of alkenes.
Scheme 32: Gold-catalyzed aminooxygenation and aminoarylation of alkenes.
Scheme 33: Gold-catalyzed carboamination, carboalkoxylation and carbolactonization of terminal alkenes with ar...
Scheme 34: Synthesis of tricyclic indolines via gold-catalyzed formal [3 + 2] cycloaddition.
Scheme 35: Gold(I) catalyzed aminoarylation of terminal alkenes in presence of Selectfluor [dppm = bis(dipheny...
Scheme 36: Mechanistic investigation on the aminoarylation of terminal alkenes by bimetallic gold(I) catalysis...
Scheme 37: Proposed mechanism for the aminoarylation of alkenes via [Au(I)-Au(I)]/[Au(II)-Au(II)] redox cataly...
Scheme 38: Oxyarylation of terminal olefins via redox gold catalysis.
Scheme 39: a) Intramolecular gold-catalyzed oxidative coupling reactions with aryltrimethylsilanes. b) Oxyaryl...
Scheme 40: Oxy- and amino-arylation of alkenes by [Au(I)]/[Au(III)] photoredox catalysis.
Graphical Abstract
Scheme 1: Gold(I)-catalyzed carbocyclization.
Scheme 2: Proposed mechanism for the gold(I)-catalyzed cyclization.
Scheme 3: Gold-catalyzed 5-exo-dig carbocyclization cascade.
Figure 1: Structure of senaequidolide (13) and ellipticine (14).
Graphical Abstract
Scheme 1: Cycloisomerization/fluorination of functionalized indoles.
Scheme 2: Synthesis of hemiaminal derivatives.
Scheme 3: Reaction on n-hexyl-substituted derivative 1i.
Scheme 4: Mechanism rationale for the formation of 7.