N-Heterocyclic carbenes (NHCs) containing triazolium motifs have emerged as a powerful tool in organocatalysis. Recently, various NHC-catalyst-mediated organic transformations have been developed. This review aims to compile the current state of knowledge on enantioselective NHC-triazolium-catalyzed named reactions as well as introduce newly developed catalytic methods. Furthermore, this review article framework provides an excellent opportunity to highlight some of the unique applications of these catalytic procedures in the synthesis of natural products and biologically active compounds, notably the extensive processes for the preparation of substituted chiral alcohols and their derivatives. This review also provides an overview of the synthesis of chiral NHC-triazolium-catalyst libraries and their applications in catalytic enantioselective reactions.

1 Introduction

2 Synthesis of N‑Heterocyclic Carbenes Containing Triazolium Motifs

2.1 Pyrrolidine-Based Triazoliums NHCs: P_x

2.2 Morpholine-Based Triazoliums NHCs: M_x

2.3 Aminoindane-Based Triazoliums NHCs: AM_x

2.4 Oxazolidine-Based Heteroazoliums NHCs: O_x

2.5. Acyclic Triazoliums NHCs: A_x

3 Enantioselective Organocatalytic Reactions

3.1 Enantioselective Benzoin Reactions

3.1.1 Aldehyde–Aldehyde Homo-Benzoin Reactions

3.1.2 Aldehyde–Aldehyde Cross-Benzoin Reactions

3.1.3 Aldehyde–Ketone Cross-Benzoin Reactions

3.1.4 Aldehyde–Imine Cross-Benzoin Reactions

3.1.5 Aza-Benzoin Reactions

3.2 Enantioselective Stetter Reactions

3.2.1 Intramolecular Stetter Reactions

3.2.2 Intermolecular Stetter Reactions

3.3 Enantioselective Diels–Alder Reactions

3.4 Enantioselective Michael Additions

3.5 Enantioselective Rauhut–Currier Reactions

3.6 Enantioselective Cycloadditions

3.7 Enantioselective Michael–Stetter Cascade Reactions

3.8 Enantioselective Annulation Reactions

3.9 Synthesis of Spiro Compounds

3.10 Heterocycle Synthesis

3.11 Carbocycle Synthesis

3.12 Asymmetric Steglich Rearrangement Reactions

3.13 NHC-Mediated Asymmetric Acylation/Hydroacylation Reactions

3.14 Enantioselective α-Fluorination of Aliphatic Aldehydes

3.15 Functionalization of Carboxylic Anhydrides by NHC Catalysis

3.16 Asymmetric β-Boration of Acyclic Enones

3.17 Synthesis of Tropane Derivatives via Organocatalysis

3.18 Dynamic Kinetic Resolution of Pyranones via NHC Catalysis

3.19 Enantioselective Umpolung Reactions

3.20 Enantioselective Esterification of Ketenes

3.21 Asymmetric Synthesis of trans-γ-Lactams

3.22 Oxy-Cope Rearrangements

3.23 Claisen Rearrangements

3.24 Enantioselective Synthesis of Complex Heterocycles

3.25 Atroposelective Synthesis of N-Aryl Succinimides

3.26 Asymmetric α-Fluorination via Cascade Reactions

4 Conclusion