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. 2021 Jul 28;121(14):8613-8684.
doi: 10.1021/acs.chemrev.0c00697. Epub 2020 Nov 2.

Gold-Catalyzed Synthesis of Small Rings

Mauro Mato  1   2 , Allegra Franchino  1   2 , Cristina Garcı A-Morales  1   2 , Antonio M Echavarren  1   2
Affiliations

Gold-Catalyzed Synthesis of Small Rings

Mauro Mato et al. Chem Rev. .

Abstract

Three- and four-membered rings, widespread motifs in nature and medicinal chemistry, have fascinated chemists ever since their discovery. However, due to energetic considerations, small rings are often difficult to assemble. In this regard, homogeneous gold catalysis has emerged as a powerful tool to construct these highly strained carbocycles. This review aims to provide a comprehensive summary of all the major advances and discoveries made in the gold-catalyzed synthesis of cyclopropanes, cyclopropenes, cyclobutanes, cyclobutenes, and their corresponding heterocyclic or heterosubstituted analogs.

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Conflict of interest statement

The authors declare no competing financial interest.

Figures

Scheme 1
Scheme 1. Estimated Ring Strain Energy Ranges for Selected Cyclic Hydrocarbons
Scheme 2
Scheme 2. Structures of Natural or Bioactive Compounds Containing Small Rings (A) and Selected Classical Approaches for the Assembly of Cyclopropanes (B) and Cyclobutanes (C)
Scheme 3
Scheme 3. Fate of Cyclopropyl Gold(I) Carbenes Generated by 1,6-Enyne Cyclization
Scheme 4
Scheme 4. Activation of Gold(I) Chloride Complexes (Left) and Stable Cationic Gold(I) Complexes (Right)
Scheme 5
Scheme 5. Mechanistic Rationale for the Generation of Metal Carbenes from Diazo-Compounds
Scheme 6
Scheme 6. Gold(I)-Catalyzed Cyclopropanation of Cyclooctene and Styrene with Ethyl Diazoacetate
Scheme 7
Scheme 7. Cyclopropanation Catalyzed by a Cationic Phosphine Gold(I) Complex
Scheme 8
Scheme 8. Gold(I) Ethylene Complexes with Triazapentadienyl Ligands in Cyclopropanation
Scheme 9
Scheme 9. Diazo–Carbene Transfer Cyclopropanation Promoted by Metallic Gold Particles
Major diastereoisomer (cis/trans) depicted for each cyclopropane.
Scheme 10
Scheme 10. Enantioselective Gold(I)-Catalyzed Cyclopropanation with Diazooxindoles
Scheme 11
Scheme 11. Enantioselective Gold(I)-Catalyzed Cyclopropanation of Enamides
R = 2,6-i-Pr2C6H3. Products obtained as the depicted trans single diastereoisomer.
Scheme 12
Scheme 12. Buchner Reaction
Scheme 13
Scheme 13. Gold(I)-Catalyzed Buchner Ring Expansion versus C–H Insertion
t-Bu3tpy = 4,4′,4″-tri-tert-butyl-2,2′:6′,2″-terpyridine.
Scheme 14
Scheme 14. Buchner versus Insertion Reaction of Acceptor Gold(I) Carbenes
Combined amount of all possible regioisomers. In all cases, the total yield for the carbene transfer from EDA was at least 94%.
Scheme 15
Scheme 15. Cyclopropanation of Naphthalene
Obtained as a mixture of the two possible regioisomers.
Scheme 16
Scheme 16. Gold(I)-Catalyzed Enantioselective Cyclopropenation of Internal Alkynes
Scheme 17
Scheme 17. Retro-Cyclopropanation Reactions: Historical Perspective
Scheme 18
Scheme 18. Retro-Buchner or Decarbenation Reaction of Cycloheptatrienes
Scheme 19
Scheme 19. Formation of Naphthalenes by Retro-Cyclopropanation of a Benzo-fused Norcaradiene
Scheme 20
Scheme 20. Retro-Buchner or Decarbenation Reaction of Cycloheptatrienes
Scheme 21
Scheme 21. Aryl Cyclopropanation by Decarbenation or Retro-Buchner Reaction
Yield and cis/trans ratio between parentheses.
Scheme 22
Scheme 22. Synthesis of cis-Vinylcyclopropanes
Scheme 23
Scheme 23. Second Generation of Cycloheptatrienes as General Metal Carbene Precursors
[Au] = [(JohnPhos)Au(MeCN)]SbF6 (5 mol %) in EtOAc at 25 °C. [Rh]= Rh2TFA4 (3 mol %) in 1,2-DCE at 25–60 °C. [Zn] = ZnBr2 (10 mol %) in 1,2-DCE at 65 °C.
Scheme 24
Scheme 24. Au(I)- or Rh(II)-Catalyzed Cyclopropanation of Enol Ethers
[Au] = [(JohnPhos)Au(MeCN)]SbF6 (5 mol %) in 1,2-DCE at the specified temperature. [Rh]= Rh2TFA4 (5 mol %) in 1,2-DCE at the specified temperature.
Scheme 25
Scheme 25. Gold(I)-Catalyzed Decarbenation of Persistent Cyclopropanes
Scheme 26
Scheme 26. Gold(I)-Carbenes by Retro-Cyclopropanation in Gas Phase
Scheme 27
Scheme 27. Characterization and Reactivity of Gold(I) Carbenes via Cyclopropenes
Scheme 28
Scheme 28. Cyclopropene Opening and Intramolecular Vinylcyclopropanation of O- and N-Tethered 1,6-Cyclopropene-enes
R = TBDPS.
Scheme 29
Scheme 29. Cyclopropane Opening and Cyclopropanation of Benzene-Tethered 1,6-Cyclopropene-enes
Scheme 30
Scheme 30. Cyclopropene Opening and Substrate-Dependent Divergent Cyclopropanation
Using [(tBuXPhos)Au(OTf)] (5 mol %) in 1,2-DCE at 100 °C, with 4 Å molecular sieves.
Scheme 31
Scheme 31. Main Au(I)-Catalyzed Cycloisomerization Pathways for 1,6-Enynes
Scheme 32
Scheme 32. Au(I)-Catalyzed Cycloisomerizations of 1,6-Enynes and Intramolecular Cyclopropanation of Dienynes
Scheme 33
Scheme 33. Au(I)-Catalyzed Intramolecular Cyclopropanation of Cyclohexadienyl Alkynes
Scheme 34
Scheme 34. Au(I)-Catalyzed Intermolecular Cyclopropanation of 1,6-Enynes with Alkenes
Scheme 35
Scheme 35. Trapping of Cyclopropyl Gold Carbenes Generated from 1,6-Enynes
(ArO)3P = (2,4-(t-Bu)2C6H3O)3P
Scheme 36
Scheme 36. Au(I)-Catalyzed Cycloisomerization of Alkylidenecyclopropanes
Scheme 37
Scheme 37. Cycloisomerization of O-Tethered 1,6-Enynes
Scheme 38
Scheme 38. Gold Complexes for Non-asymmetric Cycloisomerizations of O- and N-Tethered 1,6-Enynes
Scheme 39
Scheme 39. Gold Complexes for Enantioselective Cycloisomerizations of O- and N-Tethered 1,6-Enynes
Pd black (2.5 mol %), H2 (1 atm), Na2CO3, EtOAc/MeOH (1:1).
Scheme 40
Scheme 40. Synthesis of 2-Oxabicyclo[3.1.0]hexanes
Scheme 41
Scheme 41. Tandem Cyclization/1,5-OR Migration/Intramolecular Cyclopropanation of Dienynes
Scheme 42
Scheme 42. Gold-Catalyzed Formation of the Tricyclic Cores of Aromadendranes
Scheme 43
Scheme 43. Tandem Cyclization/1,5-OR Migration/Intermolecular Cyclopropanation of 1,6-Enynes
Scheme 44
Scheme 44. Cycloisomerization of 1,6-Ene-Ynamides
Scheme 45
Scheme 45. Gold(I)- or Pt(II)-Catalyzed Cycloisomerization of 3-Hydroxy-1,5-enynes
Scheme 46
Scheme 46. Gold(I)-Catalyzed Cycloisomerization of 1,5-Enynes
Scheme 47
Scheme 47. Gold(III)-Catalyzed Enantioconvergent Kinetic Resolution of 1,5-Enynes
Scheme 48
Scheme 48. Gold(I)-Catalyzed Cycloisomerization/C–H insertion of 1,5-Enynes and 1,4-Enallenes
Scheme 49
Scheme 49. Gold(I)-Catalyzed Dimerization of Ynamides
Scheme 50
Scheme 50. Au(III)-Catalyzed C–H Insertion/Cyclization Cascade of Ynamides
Scheme 51
Scheme 51. Evolution of Cyclopropyl Au(I) Carbenes Generated from 1,5-Enynes
Scheme 52
Scheme 52. Au(I)-Catalyzed 8-endo-dig Cyclization of 1,7-Enynes
Scheme 53
Scheme 53. Intramolecular Furanylation–Cyclopropanation Using Ynenals and Ynenones
Scheme 54
Scheme 54. Intermolecular Furanylation–Cyclopropanation Using Ynenones
Scheme 55
Scheme 55. Pt- or Au-Catalyzed Cyclization of 1,5-Allenynes
Scheme 56
Scheme 56. Au(I)-Catalyzed Cyclization of 1,5-Allenynes
Scheme 57
Scheme 57. Au(I)-Catalyzed Intermolecular Cyclopropanation of 1,6-Diynes
Scheme 58
Scheme 58. 1,2- vs 1,3-Acyloxy Migration of Au-Activated Propargylic Carboxylates
Scheme 59
Scheme 59. Reaction Mechanisms for Enynes Bearing a Propargylic Carboxylate
Scheme 60
Scheme 60. Au(I)-Catalyzed Intramolecular Cyclopropanations of 3-Acetoxy versus 3-Hydroxy 1,5-Enyne
Scheme 61
Scheme 61. AuCl3- and PtCl2-Catalyzed Cycloisomerizations in the Synthesis of Terpenoids
Scheme 62
Scheme 62. Au(III)-Catalyzed Cycloisomerizations in the Synthesis of Terpenoids
Scheme 63
Scheme 63. Au(I)-Catalyzed Rearrangements of Dienynes
[(IPr)AuCl] (2 mol %), AgBF4(2 mol %), CH2Cl2, rt, 10 min
Scheme 64
Scheme 64. Catalyst-Dependent 1,2- and 1,3-OAc Migrations on 1,6-Enynes
Scheme 65
Scheme 65. Cycloisomerizations of 1,7- and Higher Enynes for the Formation of Medium-Size Rings
Scheme 66
Scheme 66. Asymmetric Synthesis of Medium-Size Rings by Intramolecular Cyclopropanation
Scheme 67
Scheme 67. First Gold-Catalyzed Intermolecular Cyclopropanation via 1,2-OAc Migration
Scheme 68
Scheme 68. General Au-Catalyzed Alkene Cyclopropanation Using Propargylic Esters
Scheme 69
Scheme 69. Enantioselective Au(I)-Catalyzed Styrene Cyclopropanation Using Propargylic Esters
Scheme 70
Scheme 70. Synthesis of Benzonorcaradienes by Cyclopropanation–Hydroarylation Cascade
Scheme 71
Scheme 71. Synthesis of cis-Vinyl-alkynyl-cyclopropanes, Styrenes, and Fluorenes
Scheme 72
Scheme 72. (2 + 1), (3 + 2), and (4 + 3) Cycloadditions Using Propargylic Esters as Gold Carbene Precursors
Scheme 73
Scheme 73. Au(III)-Catalyzed Polymerization Using Styrene–Propargylic Ester Monomers
Scheme 74
Scheme 74. Intermolecular Cyclopropanations Using 1,6-Diynes with a Propargylic Ester Group
Scheme 75
Scheme 75. Cycloisomerization of 5-En-2-yn-1-yl Acetates
Scheme 76
Scheme 76. Gold-Catalyzed Tandem 1,3-Migration/Double Cyclopropanation of 1-Ene-4,n-diyne Esters
Scheme 77
Scheme 77. Cycloisomerization of 4-En-2-yn-1-yl Acetates
Scheme 78
Scheme 78. Chirality Transfer via Bent-Allene Gold Complexes
Scheme 79
Scheme 79. Cycloisomerization from Vinyl Allenenes
Scheme 80
Scheme 80. Formation of α-Oxo Gold Carbenes by Oxidation of Gold-Activated Alkynes
Scheme 81
Scheme 81. Mechanisms for the Formation of Bicyclo[3.1.0]hexane Skeletons via Oxidation of 1,6-Enynes
Scheme 82
Scheme 82. Comparison between Oxidative Cyclopropanations of 1,5- and 1,6-Enynes
Scheme 83
Scheme 83. Formation of Bicyclo[4.1.0] Skeletons
Scheme 84
Scheme 84. Oxidative Cycloisomerization of 1,6-Enynes
Scheme 85
Scheme 85. Enantioselective Oxidative Cycloisomerization of 1,6-Enynes Using a Carbene Ligand
Scheme 86
Scheme 86. Oxidative Cyclization of 1,6-Enynes
Scheme 87
Scheme 87. Enantioselective Oxidative Cyclization of 1,6-Enynes Using a Phosphoramidite Ligand
Scheme 88
Scheme 88. Oxidative Cyclization of Alkynyl Sulfoxides
Scheme 89
Scheme 89. Oxidative Cyclization of 1,5-Enynes
Scheme 90
Scheme 90. Oxidative Cyclization of a 1,5-Enyne in the Synthesis of (−)-Nardoaristolone B
Scheme 91
Scheme 91. Enantioselective Oxidative Cyclization of 1,5-Enynes Using a P,N-Ligand
Scheme 92
Scheme 92. Preparation of Bi- and Tricyclic Cyclopropyl Ketones via Oxidative Cyclizations
Scheme 93
Scheme 93. Oxidative Cyclopropanation of N-Allyl Ynamides
Scheme 94
Scheme 94. Gold-Catalyzed Oxidation of Electron-rich Ynamides
Scheme 95
Scheme 95. Oxidative Cyclization of 7-Ethynyl-1,3,5-cycloheptatrienes
Scheme 96
Scheme 96. Oxidative Intramolecular Cyclopropanation of Benzene Rings in N-Benzyl Ynamides
Scheme 97
Scheme 97. Oxidative Intramolecular Cyclopropanation of Benzene Rings in Benzyl Propargyl Ethers
Scheme 98
Scheme 98. Trapping of an α-Oxo Gold Carbene Intermediate by Styrene
Scheme 99
Scheme 99. Oxidative Intermolecular Cyclopropanation of Styrenes
Scheme 100
Scheme 100. Formation of α-Imino Gold Carbenes from Gold-Activated Alkynes
Scheme 101
Scheme 101. Intramolecular Cyclopropanation of 1,5-Enynes Using Iminopyridinium Ylides
Scheme 102
Scheme 102. Intramolecular Cyclopropanation of (Azido)ynamides
Scheme 103
Scheme 103. Intramolecular Cyclopropanation of Ynamides Using Sulfilimines
Scheme 104
Scheme 104. Intramolecular Cyclopropanation of Ynamides Using Anthranils
Scheme 105
Scheme 105. (4 + 3) Annulation of 3-En-1-ynamides with Isoxazoles
Scheme 106
Scheme 106. Gold(I)-Catalyzed Nitrene Transfer for Aziridine Synthesis
Starting from E-β-methylstyrene. Starting from Z-β-methylstyrene.
Scheme 107
Scheme 107. Aziridines from 2H-Azirines
Scheme 108
Scheme 108. Formal (4 + 2) Cycloaddition of Alkynes with Benzisoxazoles
Using AgSbF6 as chloride scavenger.
Scheme 109
Scheme 109. Synthesis, Characterization, and Reactivity of Metal Carbenes
Ar = p-Methoxyphenyl.
Scheme 110
Scheme 110. High Temperature Cyclopropanation Using Sulfone–Imidazolium Gold(I) Carbenoids
PMP = p-Methoxyphenyl.
Scheme 111
Scheme 111. Gold Carbenes from Chloromethyl Gold(I) Carbenoids
Scheme 112
Scheme 112. Intramolecular Cyclopropanation through Catalytic Alkene Activation with Sulfonium Ylides
Scheme 113
Scheme 113. Asymmetric Intramolecular Cyclopropanation with Sulfonium Ylides
Scheme 114
Scheme 114. Cyclopropanation of Allenamides with Sulfonium Ylides
Scheme 115
Scheme 115. Acetylene as Dicarbene Precursor
Using [(tBuXPhos)AuCl]/NaBArF4 (5 mol %) as catalyst.
Scheme 116
Scheme 116. Gold(I)-Catalyzed Cycloisomerization of Cyclopropyl 1,6-Enynes
[(JohnPhos)Au(MeCN)]SbF6. E/Z = 1:1. Reaction without H2O.
Scheme 117
Scheme 117. Mechanistic Proposal for Gold(I)-Cycloisomerization of Cyclopropyl 1,6-Enynes
Scheme 118
Scheme 118. Access to Repraesentin F and the Protoilludane Family Core
[(t-BuXPhos)Au(MeCN)]BArF4. [(JohnPhos)Au(MeCN)]SbF6.
Scheme 119
Scheme 119. Gold(I)-Catalyzed Cycloisomerization of Cyclopropyl 1,5-Enynes
Scheme 120
Scheme 120. Gold(I)-Catalyzed Cycloisomerization of Cyclopropylidene 1,6-Enynes
Reaction using [((R)-Xyl-SDP)(AuCl)2] as precatalyst.
Scheme 121
Scheme 121. Gold(I)-Catalyzed Cycloisomerization of Cyclopropylidene-Tethered Frameworks
Scheme 122
Scheme 122. Regiodivergent Gold(I)-Catalyzed Cycloisomerizations of Cyclopropylidene 1,7-Enynes
[(p-CF3C6H4)3PAuCl] (2.5 mol %) and AgSbF6 (2.5 mol %). [(DTBM-SegPhos)(AuCl)2] (10 mol %), NaBArF4 (20 mol %), toluene, rt, 96 h.
Scheme 123
Scheme 123. Enantioselective Gold(I)-Catalyzed Cycloisomerization of Cyclopropylidene 1,6-Enynes
Scheme 124
Scheme 124. Mechanistic Proposal for the Gold(I)-Catalyzed Cycloisomerization of Cyclopropylidene 1,6-Enynes
Scheme 125
Scheme 125. Gold(I)-Catalyzed Cycloisomerization of Vinylidenecyclopropanes
[((R)-Xyl-BINAP)Au2(MeCN)2](SbF6)2 (10 mol %), toluene, rt. [(Me4-tBuXPhos)Au(MeCN)]NTf2 (10 mol %). See refs ( and 662) for details.
Scheme 126
Scheme 126. Three-Component Reactions for the Synthesis of Bicyclo[3.2.0]heptanes
Scheme 127
Scheme 127. Gold(I)-Catalyzed Cyclization of 1-Epoxy-1-alkynylcyclopropanes
SiO2 filtration, [(Ph3P)AuCl] (10 mol %), AgSbF6 (10 mol %), CH2Cl2, rt.
Scheme 128
Scheme 128. Gold(I)-Catalyzed Synthesis of Cyclobutanamines
Scheme 129
Scheme 129. Intramolecular Gold(I)-Catalyzed 1,3-Acyloxy Migration/[2 + 2] Cycloaddition Sequence
AuCl3 (10 mol %), CH2Cl2, rt.
Scheme 130
Scheme 130. Intermolecular Gold(I)-Catalyzed [3,3]-Rearrangement/[2 + 2] Cycloaddition Sequence of 1,7-Enynes
Reaction performed in acetonitrile.
Scheme 131
Scheme 131. Intermolecular Gold(I)-Catalyzed 1,3-Acyloxy Shift/[2 + 2] Cycloaddition Sequence
[(Ph3P)Au(N-methyl benzotriazole)]OTf (1 mol %), CH2Cl2, rt. AgOTf (2 mol %).
Scheme 132
Scheme 132. Gold(I)-Catalyzed [2 + 2] Cycloaddition of 1,6-Allenenes
Scheme 133
Scheme 133. Experimental and Computational Mechanistic Studies on the Gold(I)-Catalyzed [2 + 2] Cycloaddition of 1,6-Allenenes
[(Ph3P)AuCl] (5 mol %), AgBF4 (5 mol %). [(Ph3P)Au]BF4 (5 mol %). [((PhO)3P)Au]BF4. [(NHC)AuCl] (5 mol %), AgSbF6 (5 mol %), CH2Cl2, −5 °C, NHC = imidazopyridine-2-ylidene derivative. A mixture of 616 (56% ee) and 616′ (52% ee) was obtained from enantioenriched 613 (>99% ee).
Scheme 134
Scheme 134. Gold(I)-Catalyzed Cycloadditions of 1,7-Allenenes
Scheme 135
Scheme 135. Gold(I)-Catalyzed Cycloadditions of Allenedienes
[((2,4-(t-Bu)2-C6H3O)3P)AuCl] (10 mol %), AgSbF6 (10 mol %), 0 °C. 622a was obtained from trans-621. 622b and 622b′ were obtained from cis-621.
Scheme 136
Scheme 136. Gold(I)-Catalyzed [2 + 2] Cycloaddition of Alkenes and Allenamides
[(JohnPhos)AuCl] (2 mol %), AgSbF6 (2 mol %), CH2Cl2, 4 Å MS, 25 °C. [((2,4-(t-Bu)2-C6H3O)3P)Au(NTf2)] (0.5 mol %), CH2Cl2, rt. [(Ph3P)AuCl] (5 mol %), AgSbF6 (2 mol %), CH2Cl2, 4 Å MS, 25 °C. Norbornene (15 mol %). Reaction without alkene partner. [((2,4-(t-Bu)2-C6H3O)3P)AuCl] (2 mol %), AgSbF6 (2 mol %), CH2Cl2, 4 Å MS, −15 °C. [(JohnPhos)Au(MeCN)]SbF6 (5 mol %), DCE, rt to 85 °C.
Scheme 137
Scheme 137. Asymmetric Gold(I)-Catalyzed [2 + 2] Cycloaddition of Alkenes and Allenamides
Scheme 138
Scheme 138. Asymmetric Gold(I)-Catalyzed [2 + 2] and [4 + 2] Cycloaddition of 3-Styrylindoles and Allenamides
Scheme 139
Scheme 139. Asymmetric Gold(I)-Catalyzed [2 + 2] Cycloaddition of Indoles and Allenes
Scheme 140
Scheme 140. Gold(I)-Catalyzed Cycloisomerization of Bisallenes
Scheme 141
Scheme 141. Gold(I)-Catalyzed Formal (3 + 2)/(2 + 2)-Annulation
Scheme 142
Scheme 142. Gold(I)-Catalyzed Cycloisomerization of 1,6-Enynes
[(CyJohnPhos)AuCl] (2 mol %), AgSbF6 (2 mol %). [(Ph3P)Au(NTf2)] (2 mol %). [(IPr)Au(PhCN)]SbF6 (5 mol %). [(JonhPhos)Au(MeCN)]SbF6 (5 mol %), CH2Cl2, 80 °C.
Scheme 143
Scheme 143. Mechanistic Proposal for the Gold(I)-Catalyzed [2 + 2] Cycloaddition of 7-Aryl-1,6-enynes
Scheme 144
Scheme 144. Gold/Silver-Catalyzed [2 + 2] Cycloaddition/Hydroarylation Sequence of 7-Aryl-1,6-enynes
Scheme 145
Scheme 145. Gold(I)-Catalyzed [2 + 2] Cycloaddition of Carbonyl-Tethered 1,6-Enynes
[(SPhos)AuCl] (5 mol %), AgSbF6 (5 mol %), rt. [(SPhos)AuCl] (5 mol %), AgSbF6 (5 mol %), CF3CH2OH, rt.
Scheme 146
Scheme 146. Gold(I)-Catalyzed [2 + 2] Cycloaddition of 1,6-Enynes and Subsequent Oxidation
Scheme 147
Scheme 147. Gold(I)-Catalyzed [2 + 2] Cycloaddition of 1,7-Enynes
[(CyJohnPhos-OMe)AuCl] (2 mol %), AgSbF6 (2 mol %), CH2Cl2, rt. [(JohnPhos)Au(NCMe)]SbF6 (2 mol %), CH2Cl2, rt. 80 °C, MW.
Scheme 148
Scheme 148. Gold(I)-Catalyzed [2 + 2] Cycloaddition of 1,7-Enynes
[(JohnPhos)AuCl] (5 mol %).
Scheme 149
Scheme 149. Gold(I)-Catalyzed [2 + 2] Cycloaddition of 1,8- and 1,9-Enynes
Scheme 150
Scheme 150. Gold(I)-Catalyzed [2 + 2] Cycloaddition of Large 1,n-Enynes (n ≥ 10)
[(t-BuXPhos)Au(MeCN)]SbF6 (3 mol %), CH2Cl2, 23 °C. [(t-BuXPhos)Au(MeCN)]BArF4 (3 mol %), CH2Cl2, 23 °C. [(IPr)Au(PhCN)]BArF4 (3 mol %), CH2Cl2, 25 °C.
Scheme 151
Scheme 151. Gold(I)-Catalyzed [2 + 2] Cycloaddition between Alkynes and Alkenes
Scheme 152
Scheme 152. Mechanistic Proposal for the Formation of Cyclobutenes and 1,3-Dienes
Scheme 153
Scheme 153. Gold(I)-Catalyzed [2 + 2] Cycloaddition of 1,3-Diynes, 1,3-Enynes, and 1,n-Dienes (n = 3,5)
[(IPr)Au(PhCN)]BArF4 (5 mol %), CH2Cl2, 23 °C. [(t-BuXPhos)Au(MeCN)]BArF4 (5 mol %), CH2Cl2, 23 °C.
Scheme 154
Scheme 154. Asymmetric Gold(I)-Catalyzed [2 + 2] Cycloaddition of Alkenes with Alkynes
C6H5Cl, −20 °C. (S,RP)-710 (2.5 mol %), NaBAr4F (2.5 mol %). (R,SP)-711 (5 mol %), NaBAr4F (5 mol %).
Scheme 155
Scheme 155. Enantioselective Total Synthesis of Rumphellaone A
Scheme 156
Scheme 156. Gold(I)-Catalyzed [2 + 2] Cycloaddition between Haloalkynes and Alkenes
Scheme 157
Scheme 157. Gold(I)-Catalyzed Oxidative Ring Expansion
Scheme 158
Scheme 158. Gold(I)-Catalyzed Cycloisomerization of Cyclopropyl 1,5-Enynes
Scheme 159
Scheme 159. Gold(I)-Catalyzed Cycloisomerization of Cyclopropylidene 1,7-Enynes
Scheme 160
Scheme 160. Gold(I)-Catalyzed Cycloisomerization of 1,7-Diyne Pivalates
Scheme 161
Scheme 161. Gold(I)-Catalyzed Cycloisomerization of 1,n-Diyne Benzoates
Scheme 162
Scheme 162. Gold(I)-Catalyzed Cycloisomerization of Diynes
[(Ph3P)Au(N-methyl benzotriazole)]OTf (1 mol %), CH2Cl2, rt. AgOTf (2 mol %).
Scheme 163
Scheme 163. Gold(I)-Catalyzed Cycloisomerization of Alkyne-Ketene N,N-Acetals
Scheme 164
Scheme 164. Dual Gold(I)-Catalyzed Synthesis of Cyclobutenes
Scheme 165
Scheme 165. Ring Expansion of 1,1-Alkynylcyclopropanols
Scheme 166
Scheme 166. Enantioselective Ring Expansion of 1,1-Allenylcyclopropanols
Scheme 167
Scheme 167. Photoredox and Gold-Catalyzed Arylative Ring Expansion
Scheme 168
Scheme 168. Ring Expansion of a 1,1-Alkenylcyclopropanol
Scheme 169
Scheme 169. Asymmetric Cycloisomerization of Cyclopropyl-Substituted 1,6-Enynes
Scheme 170
Scheme 170. Oxidative Ring-Expansion of Vinylidene Cyclopropanes
[Au] = [(Ph3P)AuCl] (5 mol %)/AgSbF6 (10 mol %). Py*–O = 3,5-dibromopyridine N-oxide.
Scheme 171
Scheme 171. Stereodivergent Synthesis of Alkylidene Cyclobutanones
Scheme 172
Scheme 172. AuCl-Catalyzed Cycloisomerization of 1,6-Ene-ynamides
Scheme 173
Scheme 173. Au(I)-Catalyzed Oxidative Rearrangement of Homopropargylic Ethers to cis-Cyclobutanones
Scheme 174
Scheme 174. Au(I)-Catalyzed Oxidative Synthesis of Cyclobutanones
Scheme 175
Scheme 175. Au(I)-Catalyzed Oxidative Synthesis of Oxetan-3-ones
Scheme 176
Scheme 176. Large-Scale Au(I)-Catalyzed Synthesis of an Oxetane–Piperidine Building Block
Scheme 177
Scheme 177. Au(I)-Catalyzed Oxidative Synthesis of Azetidin-3-ones
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