Recent Strategies in the Nucleophilic Dearomatization of Pyridines, Quinolines, and Isoquinolines

Abstract

Dearomatization reactions have become fundamental chemical transformations in organic synthesis since they allow for the generation of three-dimensional complexity from two-dimensional precursors, bridging arene feedstocks with alicyclic structures. When those processes are applied to pyridines, quinolines, and isoquinolines, partially or fully saturated nitrogen heterocycles are formed, which are among the most significant structural components of pharmaceuticals and natural products. The inherent challenge of those transformations lies in the low reactivity of heteroaromatic substrates, which makes the dearomatization process thermodynamically unfavorable. Usually, connecting the dearomatization event to the irreversible formation of a strong C-C, C-H, or C-heteroatom bond compensates the energy required to disrupt the aromaticity. This aromaticity breakup normally results in a 1,2- or 1,4-functionalization of the heterocycle. Moreover, the combination of these dearomatization processes with subsequent transformations in tandem or stepwise protocols allows for multiple heterocycle functionalizations, giving access to complex molecular skeletons. The aim of this review, which covers the period from 2016 to 2022, is to update the state of the art of nucleophilic dearomatizations of pyridines, quinolines, and isoquinolines, showing the extraordinary ability of the dearomative methodology in organic synthesis and indicating their limitations and future trends.

Figure 1

Reactive sites of pyridines, quinolines, isoquinolines, and their salts.

Scheme 1. Stepwise Dearomatization/Enantioselective Cu(I)-Catalyzed Borylation of Pyridines

Scheme 2. Copper(I)-Catalyzed Regio- and Enantioselective Protoborylation of 1,2-Dihydroquinolines

Scheme 3. Kinetic Resolution of 2-Substituted 1,2-Dihydroquinolines by Asymmetric Cu-Catalyzed Borylation

Scheme 4. Cu-Catalyzed Regio- and Enantioselective Hydroboration of 1,2-Dihydroquinolines

Scheme 5. Asymmetric Cu(I)-Catalyzed Direct 1,4-Dearomatization of Pyridines

Scheme 6. Regioselective Heterobinuclear Cu/Fe-Catalyzed 1,4-Hydroboration of Pyridines

Scheme 7. Copper-Catalyzed Regio- and Diastereoselective Reaction of Pyridinium Salts with Diborylalkyl Reagents

Scheme 8. Copper-Catalyzed Enantioselective Dearomative Borylation of 4-Quinolinols

Scheme 9. Nickel-Catalyzed Regioselective 1,4-Hydroboration of Pyridines

Scheme 10. 1,2-Hydroboration of Pyridines Catalyzed by a Cooperative Ni–O Catalyst

Scheme 11. Ruthenium-Catalyzed Regioselective 1,4-Hydroboration of Pyridines

Scheme 12. Ruthenium-Catalyzed Regioselective 1,2-Hydrosilylation of Quinolines

Scheme 13. Zinc-Catalyzed 1,2-Hydrosilylation and Hydroboration of N-Heterocycles

Scheme 14. Regioselective Hydroboration and Hydrosilylation of N-Heteroarenes Catalyzed by a Zinc Alkyl Complex

Scheme 15. Partial Transfer Hydrogenation of Quinolines through Cobalt-Amido Cooperation with Ammonia Borane

Scheme 16. Cobalt-Catalyzed Selective 1,4-Dearomatization of Pyridines

Scheme 17. Ir-Catalyzed Dearomative 1,2-Hydrosilylation of Quinolines and Pyridines

Scheme 18. Zr^IIIH-BTC-Catalyzed 1,4-Dearomative Hydroboration and Hydrosilylation of Pyridines and Quinolines

Scheme 19. Ti₃-BPDC-CoH-Catalyzed Cascade Reduction of Pyridines and Quinolines

Scheme 20. One-Pot Rhodium-Catalyzed Dearomative Hydroboration/Hydrogenation of Fluorinated Pyridines

Scheme 21. Iron-Catalyzed 1,2-Selective Hydroboration of N-Heteroarenes

Scheme 22. Thorium-Catalyzed 1,2-Selective Hydroboration of N-Heteroarenes

Scheme 23. Magnesium-Catalyzed Regioselective 1,2-Hydroboration of N-Heteroarenes

Scheme 24. Reductive Dearomatization of Pyridines and Isoquinolinium Salts

Scheme 25. Dearomatization of Pyridines, Quinolines, and Isoquinolines with Trimethylamine Borane as Mild Reducing Agent

Scheme 26. Interrupted Dearomative Reduction Strategy of Chalcone-Derived Pyridinium Salts

Scheme 27. Reductive Functionalization of Quinolinium and Isoquinolinium Salts with Michael Acceptors

Scheme 28. Hydride Transfer-Initiated Synthesis of 3-Functionalized Quinolines from N-Isoquinolinium Salts and 2-Aminobenzaldehydes

Scheme 29. B(C₆F₅)₃-Catalyzed Hydrogenation of N-Heterocycles with Ammonia Borane

Scheme 30. B(C₆F₅)₃-Catalyzed Cascade Reduction of Pyridines

Scheme 31. B(C₆F₅)₃-Catalyzed Hydrogenative Reduction of N-Aromatic Rings

Scheme 32. One-Pot Dearomative Hydrosilylation of Quinolines and Enamine-Azide (3 + 2) Cycloaddition

Scheme 33. Borane-Catalyzed Chemoselective and Enantioselective Reduction of 2-Vinyl-Substituted Pyridines

Scheme 34. Hydrosilylation of Quinolines Catalyzed by B(C₆F₅)₃ or by a Silylinium Ion

Scheme 35. Borenium-Catalyzed Reduction of Pyridines with Hydrogen and Hydrosilane

Scheme 36. Borane-Catalyzed Reduction of Pyridines via Hydroboration/Hydrogenation Cascade

Scheme 37. Kinetic Resolution of Axially Chiral 5- or 8-Substituted Quinolines via Asymmetric Transfer Hydrogenation

Scheme 38. Enantioselective Transfer Hydrogenation of Quinolin-3-tosylamines

Scheme 39. Enantioselective Dearomatization of 2-Substituted Quinolines Catalyzed by a Porous Chiral Phosphoric Acid

Scheme 40. Regioselective 1,4-Hydroboration of Pyridines Catalyzed by an Acid-Initiated Boronium Cation

Scheme 41. Regioselective Hydroboration of Pyridines Mediated by Phosphorus-Based Catalysts

Scheme 42. Potassium tert-Butoxide-Promoted Regioselective Hydroboration of N-Heteroarenes

Scheme 43. Regioselective Hydroboration of N-Heteroarenes with a Potassium-Based Catalyst

Scheme 44. NHC-Parent Silyliumylidene Cation for the 1,4-Regioselective Hydroboration of N-Heteroarenes

Scheme 45. NHC-Catalyzed 1,2-Regioselective Hydroboration of Quinolines

Scheme 46. Iodine-Catalyzed Reduction of Quinolines with HBpin

Scheme 47. Generation of Pyridinium Ylides

Scheme 48. Synthesis of Tetrahydroindolizines through the Formation of Pyridinium Ylides from Diazo Compounds

Scheme 49. Proposed Mechanism to Rationalize the Synthesis of Spiroindolizidine Oxindoles through Cycloaddition of Pyridinium Ylides

Scheme 50. Asymmetric Synthesis of Tetrahydroindolizines by Bimetallic Relay Catalyzed Cycloaddition of Pyridinium Ylides with Oxindoles

Scheme 51. Base-Promoted Cascade Reaction of 3-(1-Alkynyl)chromones with Pyridinium Ylides

Scheme 52. Synthesis of Azepines by Visible Light-Mediated Dearomative Ring Expansion of Pyridinium Ylides

Scheme 53. Synthesis of Policyclic Azepines by Visible-Light-Mediated Dearomative Ring Expansion of Isoquinolinium and Quinolinium Ylides

Scheme 54. Diastereoselective Dearomative (3 + 2) Cycloaddition with In Situ Generated Pyridinium Ylides

Scheme 55. Blue LED-Mediated (3 + 2) Cycloaddition with Pyridinium and Isoquinolinium Ylides from Aryl Diazoesters

Scheme 56. Rhodium-Catalyzed Dearomatization of O-Substituted Pyridines with Diazocompounds for the Synthesis of N-Substituted 2-Pyridones

Scheme 57. 1,3-Dipolar Cycloaddition of Quinolinium Ylides with Isatylidene Malononitriles

Scheme 58. 1,3-Dipolar Cycloaddition Reaction of Quinolinium Ylides with Arylidene Malononitriles and Maleimide

Scheme 59. Rhodium-Catalyzed Regiodivergent (3 + 2) and (5 + 2) Cycloadditions of Quinolinium Ylides with Alkynes

Scheme 60. Cycloaddition Reaction of Quinolinium Ylides with 1,3-Indanedione and 2-Arylidene-1,3-indanediones

Scheme 61. Enantioselective Inverse-Electron Demand 1,3-Dipolar Cycloaddition of Isoquinolinium Methylides with Enecarbamates

Scheme 62. (3 + 2)-(4 + 2)-(3 + 2) Cycloaddition Sequence of Isoquinolinium Ylides with Aromatic Aldehydes and Indan-1,3-dione

Scheme 63. Three-Component Reaction of Isoquinolinium Salts, Isatins, and Malononitrile

Scheme 64. Tandem Double (3 + 2) Cycloaddition Reactions of N-Cyanomethylisoquinolinium Ylides

Scheme 65. One-Pot Four-Component Synthesis of Benzanulated Indolizidine Scaffolds

Scheme 66. Diastereoselective Synthesis of Spirocyclic Isoxazolo[5,4-c]pyrrolo[2,1-a]isoquinolines via Cascade Double (3 + 2) Cycloadditions

Scheme 67. Regio- and Stereoselective Three-Component (3 + 2) Cycloaddition Reaction of Isoquinolinium Ylides and Indeno-quinoxaline Derivatives

Scheme 68. Enantioselective (3 + 3) Cycloaddition Reaction of Diazocompounds with Isoquinolinium Methylides

Scheme 69. Formal (5 + 3) Cycloaddition of Zwitterionic Allylpalladium Intermediates with Azomethine Imines

Scheme 70. NHC-Catalyzed Enantioselective (3 + 2) Dearomatizing Annulation of Saturated Carboxylic Esters with N-Iminoisoquinolinium Ylides

Scheme 71. Diastereoselective 1,3-Dipolar Cycloaddition of Quinolinium Imides with Acrylates, Maleimides, and Benzynes

Scheme 72. Enantioselective Copper(I)-Catalyzed Reaction of Enoldiazo-ketones and -amides with Acyliminopyridinium Ylides

Scheme 73. Palladium-Catalyzed (4 + 3) Dearomatizing Cycloaddition Reaction of N-Imino-quinolinium and -isoquinolinium Ylides

Scheme 74. Rh(II)-Catalyzed Formation of Isolable Azomethine Ylides

Scheme 75. Synthesis of Fused Polycyclic 1,4-Benzodiazepines via Cascade (5 + 2)/(2 + 2) Cycloadditions

Scheme 76. Rh(II)-Catalyzed (5 + 3) Cycloaddition of Pyridinium Zwitterions and Enol Diazoacetates

Scheme 77. Pd(0)-Catalyzed (4 + 2) Cycloaddition of Pyridinium Zwitterions and γ-Methylidene-δ-valerolactone

Scheme 78. Gold-Catalyzed (5 + 2) Cycloaddition of Quinolinium Zwitterions and Allenamides

Scheme 79. Palladium-Catalyzed Reaction of Pyridinium Zwitterions with Trimethylenemethane via Dearomative (3 + 2) Cycloaddition and Intramolecular Cyclization

Scheme 80. (5 + 2) Cycloaddition Reaction of N-Aromatic Zwitterions with In Situ Generated Ketenes

Scheme 81. Cu(I)-Catalyzed (5 + 1) Cycloaddition Reaction of Quinolinium Zwitterions and Alkynes

Scheme 82. Cyclopropanation of Quinolinium Zwitterions via Site- and Stereoselective Dearomative Cycloadditions

Scheme 83. Silver-Catalyzed Ring Expansion Reaction of Quinolinium Zwitterions through 1,4-Dearomative Addition of Diazoacetates

Scheme 84. Coordination-Driven Regioselective 1,2-Dearomatizations of Quinolinium Zwitterions

Scheme 85. Enantioselective Copper-Catalyzed (5 + 3) Cycloaddition between Quinolinium Zwitterions and Enol Diazoacetates

Scheme 86. Sequential 1,3-N- to C- and 1,3-C- to C-Migrations of Sulfonyl Groups in Aza-(5 + 2) Cycloaddition of Indoloazomethine Ylides

Scheme 87. Cyclization Reaction of Pyridinium 1,4-Zwitterionic Thiolates and Arynes

Scheme 88. Formal (5 + 1) Cycloaddition Reaction of Pyridinium 1,4-Zwitterionic Thiolates with Sulfenes

Scheme 89. 1,5-Dipolar Cycloaddition Reaction between Pyridinium 1,4-Zwitterionic Thiolates and Activated Allenes

Scheme 90. Formal (4 + 2) Cycloaddition Reaction of Pyridinium 1,4-Zwitterionic Thiolates with 1-Sulfonyl-1,2,3-triazoles

Scheme 91. Cyclopropanation of Quinolinium Zwitterionic Thiolates via Dearomative Reactions with Sulfur Ylides

Scheme 92. Decarboxylative Cascade Cyclization of Propargylic Cyclic Carbonates/Carbamates and Pyridinium 1,4-Zwitterionic Thiolates

Scheme 93. Visible-Light-Induced (1 + 5) Annulation of Phosphoryl Diazomethylarenes and Pyridinium 1,4-Zwitterionic Thiolates

Scheme 94. Metal-Free Reactions of 1,4-Diynes and 1-En-4-yn-3-ones with Isoquinoline and Quinoline N-Oxides

Scheme 95. Catalytic Asymmetric Tandem Cycloisomerization/(5 + 2) Cycloaddition Reaction of N-Aryl Nitrone Alkynes with Methyleneindolinones

Scheme 96. Tandem Reactions of Isoquinoline-Derived Huisgen’s 1,4-Dipoles with Various Alkene Dipolarophiles

Scheme 97. Tandem Cyclizations of Pyridine-Derived Huisgen’s 1,4-Dipoles with Various Dipolarophiles

Scheme 98. Reactivity of Isoquinoline-Derived Huisgen 1,4-dipoles In Situ-Prepared from Methyl Perfluoroalk-2-ynoates

Scheme 99. Catalyst-Free Annulation Reactions of Quinolines and Pyridines with Electron-Deficient Acetylenes

Scheme 100. Three-Component Reactions Involving Huisgen’s Zwitterionic 1,4-Dipole Intermediates

Scheme 101. Enantioselective Dearomative Three-Component Reaction of Isoquinolines and Pyridines, Allenoates, and Methyleneindolinones

Scheme 102. 1,3-Dipolar Cycloaddition of 2-Substituted 3,5-Dinitropyridines and Unstabilized N-Methyl Azomethine Ylide

Scheme 103. Enantioselective Dearomative (3 + 2) Annulation Reaction of Isoquinolines with Zwitterionic Intermediates from Isocyanides and Alkylidene Malonates

Scheme 104. (4 + 3) Cycloaddition Reactions of N-Methyloxidopyridinium Ion with Dienes

Scheme 105. Dearomative Trifunctionalization of Pyridinium Salts by Reaction with Multifunctional o-Hydroxyl Aromatic Azomethine Ylides

Scheme 106. Dearomative Multifunctionalization of Quinolinium Salts through Reaction with o-Hydroxyl Aromatic Azomethines

Scheme 107. Dearomatization of Nitro(iso)quinolines through (4 + 2) Cycloaddition with Silyloxydienes under High Pressure

Scheme 108. Copper-Catalyzed Bis-annulations of Malonate-Tethered O-Acyl Oximes with Pyridine Derivatives

Scheme 109. Enantioseelctive Copper-Catalyzed O-to-N (1,3)-Rearrangement of 2-Propargyloxy-Pyridines

Scheme 110. Brønsted Acid-Enhanced Copper-Catalyzed Atroposelective Cycloisomerization to Axially Chiral Arylquinolizones via Dearomatization of Pyridine

Scheme 111. Buchwald–Hartwig Coupling/Pyridine Dearomatization Sequence in Eucalyptol

Scheme 112. Pd-Catalyzed C(sp²)–H Cyclizative Carbonylation of 2-Benzylpyridines

Scheme 113. Palladium-Catalyzed Hydrocarbonylative Cyclization of Pyridine-Tethered Alkenes and Dienes

Scheme 114. Palladium-Catalyzed Dearomative Cyclocarbonylation of Allyl Alcohols

Scheme 115. Tandem Pd-Catalyzed Allylic Alkylation/Allylic Dearomatization Reaction of N-Heteroarenes

Scheme 116. Palladium-Catalyzed Difunctionalization of Allenes through Relay Coupling with Propargylic Pyridines

Scheme 117. Dearomative Migratory Rearrangement of 2-Oxypyridines with N-Sulfonyl-triazoles and Pyridotriazoles

Scheme 118. Rhodium-Catalyzed Dearomative Rearrangement of 2-Oxypyridines with Cyclopropenes

Scheme 119. Rhodium-Catalyzed Dearomative Migratory Rearrangement of 2-Oxypyridines with Diazocompounds

Scheme 120. Silver(I)-Catalyzed Dearomatization of Pyridine-ynones for the Synthesis of Quinolizinone Derivatives

Scheme 121. Gold-Catalyzed Aminoalkynylation of Alkynes for the Synthesis of Quinolizinone Derivatives

Scheme 122. One-Pot Multicomponent Approach to Quinolizinones from 2-Substituted Pyridines via Orthogonal Tandem Catalysis

Scheme 123. Yb-Catalyzed Dearomative (3 + 2) Annulation Reactions of Quinolines and Pyridines with 2-Aminocyclopropanes

Scheme 124. Iridium-Catalyzed Intramolecular Asymmetric Allylic Alkylation of Hydroxyquinolines

Scheme 125. Scandium-Catalyzed Dearomative Spiro-annulation of Quinolines with Alkynes

Scheme 126. Metal-Free Synthesis of Tetracyclic Pyrido and Pyrazino Thienopyrimidinones

Scheme 127. One-Pot Synthesis of 3-Substituted Quinolizinones from 2-Methylene Pyridines and Alkynyl Esters

Scheme 128. Redox-Neutral Metal-Free Three-Component Carbonylative Dearomatization of Pyridine Derivatives with CO₂

Scheme 129. Double Cross-Dehydrogenative-Coupling Cyclization of N-(2-Pyridyl)amidines Mediated by CBr₄

Scheme 130. Cascade Michael Addition/Cyclocondensation Reaction of Chromone-3-carboxaldehydes with 2-Methylenepyridine Derivatives

Scheme 131. HFIP-Promoted Intramolecular Dearomative Annulation of Pyridylacetate Derivatives

Scheme 132. DBU-Catalyzed Dearomative Annulation of 2-Pyridylacetates with α,β-Unsaturated Pyrazolamides

Scheme 133. Synthesis of Functionalized Quinolizine Scaffolds via the Dearomative Annulation of 2-Pyridylacetates with Nitroenynes

Scheme 134. Visible-Light-Mediated Aerobic Oxidation of N-Alkylpyridinium Salts under Organic Photocatalysis with Eosin Y

Scheme 135. Photoredox-Catalyzed formal (3 + 2) Cycloaddition of N-Aryl α-Amino Acids with Isoquinoline N-Oxides

Scheme 136. Ir-Mediated Dearomative Photocatalytic Synthesis of Bridged 1,3-Diazepanes

Scheme 137. Dearomatization-Enabled Visible-Light-Induced 1,2-Alkylsulfonylation of Alkenes with Sodium Sulfinates and Pyridinium Salts

Scheme 138. Cooperative Photoredox/Nickel Catalysis for Cross-Electrophile Coupling of Aziridines with Pyridinium Salts

Scheme 139. Organophotoredox Approach for the Dearomatization of Quinolones and Isoquinolines with Azoles

Scheme 140. Direct Reduction of Quinolines and Isoquinolines Using Visible-Light Photoredox Catalysis

Scheme 141. Dearomative (4 + 2) Cycloaddition Reaction of Pyridines Mediated by a Polymer Immobilized Ir-Based Photocatalyst

Scheme 142. Photochemical Intermolecular Dearomative (4 + 2) Cycloaddition Reaction of (Iso)quinolines with Alkenes

Scheme 143. Photochemical Dearomative Cycloadditions of Quinolines and Alkenes or Allenes

Scheme 144. Photocatalytic Cascade Dearomative (2 + 2) Cycloaddition/Cyclopropanation Reaction of Quinolines with Alkenes

Scheme 145. Photocatalytic Cascade Dearomative (2 + 2) Cycloaddition/Cyclobutane Rearrangement of Quinolines with Alkenes

Scheme 146. Catalytic Dearomative syn-1,4-Diamination via Visible-Light-Mediated (4 + 2) Cycloaddition/Pd-Catalyzed Allylic Amination of Quinolines

Scheme 147. Light-Promoted Dearomative Cross-Coupling of Heteroarenium Salts and Aryl Iodides via Nickel Catalysis

Scheme 148. Synthesis of N-Alkylated 4-Pyridones by Copper-Catalyzed Intermolecular Asymmetric Propargylic Amination

Scheme 149. Cu-Catalyzed 1,4-Difunctionalization of Isoquinolinium Salts through an Atom-Transfer Radical Process

Scheme 150. Cu-Catalyzed Difunctionalization of Quinolinium Salts through an Atom-Transfer Radical Process

Scheme 151. Cu-Catalyzed 1,2-Difunctionalization of Isoquinolines Salts via a Radical Addition/Reduction Process

Scheme 152. Copper-Catalyzed Dearomatization and Difunctionalization of Pyridines with N-Aryl Bromodifluoroacetamides

Scheme 153. Cu/(Ph-pybox)-Catalyzed Asymmetric Dearomative Alkynylation of Isoquinolines

Scheme 154. N-Alkylation/Alkenylation Tandem Process for the Construction of 1,2-Difunctionalized Quinoline Derivatives

Scheme 155. 1,2-Reductive Dearomatization of Quinolines and Copper(I) Hydride-Catalyzed Asymmetric Hydroamination

Scheme 156. Reductive C3-Hydroxymethylation of Pyridinium and Quinolinium Salts through Iridium-Catalyzed Interrupted Transfer Hydrogenation

Scheme 157. Iridium/Acid-Cocatalyzed Synthesis of Fused Indoles via Transfer Hydrogenative Annulation of Quinolines and 1,2-Diketones

Scheme 158. Time-Dependent Enantiodivergent Allylic Amination of Hidroxiquinolines Using the Same Chiral Ir Catalyst

Scheme 159. Iridium-Catalyzed Intermolecular Asymmetric Allylic Amination with Hydroxypyridines

Scheme 160. Iridium-Catalyzed Propenylation Reactions of 4-Hydroxypyridines with Allylic Carbonates

Scheme 161. Iridium-Catalyzed Reductive Three-Component Annulation Reaction with Quinolinium Salts

Scheme 162. Reductive Annulation of Quinolines and Conjugated Enones by a MOF-Derived Iridium Catalyst

Scheme 163. C–C Bond-Forming Dearomatizations of Pyridines and Quinolines

Scheme 164. Nucleophilic Dearomatization of N-Heterocycles with Grignard Reagents Enabled by Chiral Copper Catalysis

Scheme 165. Regioselective Asymmetric Alkynylation of N-Alkyl Pyridiniums with Grignard Reagents

Scheme 166. Enantioselective Rhodium(I)-Catalyzed Dearomative Arylation or Alkenylation of N-Alkylquinolinium Salts

Scheme 167. Rhodium-Catalyzed Enantioselective Dearomatizaton of Pyridinium Salts

Scheme 168. Regiodivergent and Stereoselective Transition Metal-Catalyzed Addition of 4-Pyridones to Allenes

Scheme 169. Rh-Catalyzed Chemo- and Enantioselective Insertion of Furyl Carbenes into the N–H Bond of 2-Pyridones

Scheme 170. Regio- and Diastereoselective Three-Component Reactions via Trapping of Ammonium Ylides with Quinolinium Salts

Scheme 171. Palladium-Catalyzed Diastereoselective Three-Component Reaction of N-Aryl Diazoamides, Pyridines, and Chloroformates

Scheme 172. Sequential Pyridine Dearomatization/Mizoroki–Heck Cyclization for the Synthesis of Fused (Dihydropyrido)isoindolinone Derivatives

Scheme 173. Palladium-Catalyzed Regio- and Enantioselective Amination of Vinyl Cyclic Carbonates with 2-Hydroxypyridines

Scheme 174. Ruthenium-Catalyzed Dearomatization of Isoquinolines with Alkyl Chlorides

Scheme 175. Ru-Catalyzed Cascade Enantioselective Hydrogenation and Reductive Amination for the Construction of Chiral Julolidine Derivatives

Scheme 176. Ruthenium-Catalyzed Chemoselective N–H Bond Insertion Reactions of 2-Hydroxypyridines with Sulfoxonium Ylides

Scheme 177. Ruthenium-Catalyzed Dearomative Hydroxymethylation of Pyridines

Scheme 178. Ruthenium-Catalyzed Three-Component Reaction among Quinolinium Salts, Paraformaldehyde, and Phenols or Naphthols

Scheme 179. Ruthenium-Catalyzed Reductive Annulation Reaction of Quinolinium Salts with Indoles and Paraformaldehyde

Scheme 180. Nickel-Catalyzed Enantioselective Arylation of Pyridine

Scheme 181. Molybdenum-Promoted Synthesis of Isoquinuclidines with Bridgehead CF₃ Groups

Scheme 182. Hydrogen-Transfer Dearomative Coupling of Quinolinium Salts and Tetrahydroquinolines Catalyzed by Nitrogen-Doped Carbon Supported Nanocobalt Catalyst

Scheme 183. Dearomative Functionalization of 4-Pyridineboronic Acid Pinacol Ester

Scheme 184. Enantioselective Reissert-Type Dearomatization of Isoquinolines with Triazole-Based Anion-Binding Catalysts

Scheme 185. Enantioselective Dearomatization of Isoquinolines by a Thiourea-Based Anion-Binding Catalyst

Scheme 186. Triazole-Based Anion-Binding Catalysis for the Enantioselective Reissert-Type Dearomatization of Quinolines and Pyridines with Phosphorous Nucleophiles

Scheme 187. Nucleophile Screening in Triazole-Based-Catalyzed Reissert-Type Reactions

Scheme 188. Nucleophilic Dearomatization of Pyridines by Enantioselective Addition of Indoles to Activate N-Benzylpyridinium Salts

Scheme 189. Enantio- and Diastereoselective Nucleophilic Addition of N-tert-Butylhydrazones to Isoquinolinium Ions through Anion-Binding Catalysis

Scheme 190. Enantioselective Dearomative Arylation of Isoquinolines

Scheme 191. Chiral Phosphoric Acid-Catalyzed Dearomatization Reaction of Isoquinolines with Indole Derivatives

Scheme 192. Phosphoric Acid-Catalyzed Enantioselective Dearomative Phosphonation of Isoquinolines

Scheme 193. Construction of Tropane Derivatives by Organocatalytic Asymmetric Dearomatization of Isoquinolines

Scheme 194. Enantioselective NHC-Catalyzed Nucleophilic Dearomatization of Alkyl Pyridiniums

Scheme 195. Enantioselective Dearomatization of Alkylpyridiniums by NHC-Catalyzed Nucleophilic Acylation

Scheme 196. Organocatalytic Stereoselective Addition of Aldehydes to Acylquinolinium Ions

Scheme 197. Organocatalytic Stereoselective Addition of Aldehydes to N-Alkylpyridinium Salts

Scheme 198. Asymmetric Dearomative formal (4 + 2) Cycloadditions of N,4-Dialkylpyridinium Salts and Enones

Scheme 199. Asymmetric Cascade Multiple Functionalization of Pyridinium Salts with o-Hydroxybenzylidene Acetones

Scheme 200. Asymmetric Cascade Multiple Functionalization of Pyridinium Salts with Cyclic 2,4-Dienones

Scheme 201. Enantioselective Michael Addition of 2-Hydroxypyridines to α,β-Unsaturated 1,4-Dicarbonyl Compounds

Scheme 202. Bifunctional Lewis Base-Catalyzed Asymmetric N-Allylic Alkylation of 2-Hydroxypyridines

Scheme 203. Catalytic Enantioselective Synthesis of 1,4-Dihydropyridines via the Addition of C(1)-Ammonium Enolates to Pyridinium Salts

Scheme 204. Aryne-Induced Dearomative Phosphonylation of Quinolines

Scheme 205. Formal Insertion of N-Heteroarenes and Arynes into the C–Cl Bond of Carbon Tetrachloride

Scheme 206. Aryne Triggered Dearomatization Reaction of Isoquinolines and Quinolines with Chloroform

Scheme 207. Metal-Free Reductive Hydroxymethylation of Isoquinolines

Scheme 208. Dearomatization of Chalcone-Based Pyridinium Salts to Access Bibridged Benzoazepines

Scheme 209. Base-Promoted Dearomative Multifunctionalization of Pyridinium Salts

Scheme 210. Base-Promoted Dearomative Trifunctionalization of Isoquinolinium Salts

Scheme 211. Base-Promoted Dearomative Tri- and Bifunctionalization of Quinolinium Salts

Scheme 212. Diastereoselective Dearomative Multifunctionalization of N-Alkyl Activated Aza-arenes with 1,5-Diazapentadienium Salts

Scheme 213. Skeletal Remodeling of Chalcone-Based Pyridinium Salts

Scheme 214. Direct C–H Sulfonylimination of Pyridinium Salts

Scheme 215. Regioselective Dearomatization of N-Alkylquinolinium and Pyridinium Salts under Morita–Baylis–Hillman Conditions

Scheme 216. Nucleophilic Dearomatization of Isoquinolines via Three-Component Reaction of 3-Haloisoquinolines, Alkyl Halides, and Indoles

Scheme 217. Selective 1,4-Difunctionalization of In Situ-Activated Quinolines with Nucleophiles

Scheme 218. Iodine-Mediated Pyridine Ring Expansion for the Construction of Azepines

Scheme 219. Iodine-Catalyzed Oxidative N-Alkylation/Amidation Cascade Reaction of Isoquinolines with Benzylic C–H Bonds

Scheme 220. NHP-Promoted Regioselective Phosphonylation Reaction of Quinolines

Scheme 221. Selective N-Alkylation of 2-Hydroxypyridines with Organohalides under Catalyst and Base-Free Conditions

Scheme 222. Pyrrole-Based Anion Binding Catalysis for the Mannich-Type Reaction of N-Acyl Heteroarenium Chlorides

Scheme 223. Catalyst-Free Decarboxylative Dearomatization of Isoquinolines with β-Keto Acids and Sulfonyl Chlorides in Water

Scheme 224. Dearomatization Strategy for the Synthesis of Alstoscholarisine H

Scheme 225. Dearomatization Strategy for the Synthesis of Tetrahydroberberine

Scheme 226. Dearomatization Strategy for the Synthesis of Altemicidin

Scheme 227. Dearomatization Strategy for the Synthesis of Nuphar Indolizidine

Scheme 228. Dearomatization Strategy for the Synthesis of (+)-Isomatrine

Scheme 229. Dearomatization Strategy for the Synthesis of Lisergol

Scheme 230. Dearomatization Strategy for the Synthesis of Daphnicyclidin A