Recent Advances in the Synthesis of Diverse Libraries of Small-Molecule Building Blocks in Ionic Liquids (ILs)

The Account describes recent advances, from the authors’ laboratories, in the synthesis of diverse libraries of small-molecule building blocks employing ionic liquids (ILs). The ability of ILs to act as catalysts/promoters/solvents for electrophilic and onium ion chemistry, as well as in metal-mediated cross-coupling reactions, and the potential to sequence/hyphenate these methods, have opened up new opportunities for facile assembly of functional small molecules with increased complexity from readily available precursors. While Bronsted acidic IL/IL solvent mixtures are suitable media for carbocation and onium ion chemistry, piperidine-appended IL/IL solvent mixtures can successfully catalyze a variety of base-catalyzed reactions. Several widely practiced transformations including ‘name reactions’ were adapted and performed efficiently in ILs. 1 Introduction 2 Aryldiazonium Salts and Aryltriazenes as Coupling Partners in Metal-Mediated C–C Cross-Coupling Reactions in ILs 3 Expanding the Scope of Metal-Mediated Cross-Coupling Reactions in ILs 4 Application of ILs in Synthesis and Functionalization of Hetero­cycles 5 Expanding the Scope of Amide Synthesis in ILs 6 Generation and Chemistry of ‘Tamed’ Propargylic Cations in ILs 7 Newer Nitration Methods for Arenes and Heteroarenes in ILs 8 Halofunctionalization in ILs 9 ‘Name Reactions’and Other Widely Practiced Synthetic Transformations in ILs 9.1 The Biginelli Reaction 9.2 Nitrile Synthesis by the Schmidt Reaction 9.3 Rupe Rearrangement 9.4 Synthesis of 1,3-Dioxanes via Prins Reaction in [BMIM(SO3H)][OTf] 9.5 Synthesis of Cyclopropanes and Oxiranes by the Corey–Chaykovsky (CC) Reaction 10 Conclusions and Closing Remarks