The article reviews the development of organocatalytic reactions enabled by N-heterocyclic carbenes (NHCs), focusing on their synthesis, properties, and applications in catalysis. It begins by highlighting the historical significance of NHCs in transition metal catalysis and their role in organocatalysis, particularly in the benzoin reaction and umpolung catalysis. The evolution of NHC-based organocatalysts, especially triazolylidene carbenes, is discussed, noting their widespread use and the development of chiral scaffolds that enhance stereoselectivity. The synthesis of various NHC precursors, including thiazolium, imidazolium, and triazolium derivatives, is detailed, along with their structural diversity and reactivity. The article also explores the acidity of NHCs, their Lewis basicity, and nucleophilicity, which are crucial for their catalytic activity. The benzoin reaction is a central topic, with a focus on enantioselective variants and cross-benzoin reactions. The Stetter reaction is also extensively discussed, highlighting its intramolecular and intermolecular forms, as well as its enantioselective applications. The article covers various aspects of the Stetter reaction, including the use of different catalysts, the role of enol ethers, and the impact of fluorine on catalytic efficiency. Additionally, the hydroacylation of double and triple bonds is explored, with a focus on the mechanism and enantioselective hydroacylation of tethered styrenes. The article also discusses extended Breslow intermediates and their role in umpolung reactions, including the cyanide-catalyzed formation of saturated esters and the NHC-catalyzed homoenolate reaction. Overall, the review emphasizes the importance of NHCs in organocatalysis and their diverse applications in various chemical transformations.The article reviews the development of organocatalytic reactions enabled by N-heterocyclic carbenes (NHCs), focusing on their synthesis, properties, and applications in catalysis. It begins by highlighting the historical significance of NHCs in transition metal catalysis and their role in organocatalysis, particularly in the benzoin reaction and umpolung catalysis. The evolution of NHC-based organocatalysts, especially triazolylidene carbenes, is discussed, noting their widespread use and the development of chiral scaffolds that enhance stereoselectivity. The synthesis of various NHC precursors, including thiazolium, imidazolium, and triazolium derivatives, is detailed, along with their structural diversity and reactivity. The article also explores the acidity of NHCs, their Lewis basicity, and nucleophilicity, which are crucial for their catalytic activity. The benzoin reaction is a central topic, with a focus on enantioselective variants and cross-benzoin reactions. The Stetter reaction is also extensively discussed, highlighting its intramolecular and intermolecular forms, as well as its enantioselective applications. The article covers various aspects of the Stetter reaction, including the use of different catalysts, the role of enol ethers, and the impact of fluorine on catalytic efficiency. Additionally, the hydroacylation of double and triple bonds is explored, with a focus on the mechanism and enantioselective hydroacylation of tethered styrenes. The article also discusses extended Breslow intermediates and their role in umpolung reactions, including the cyanide-catalyzed formation of saturated esters and the NHC-catalyzed homoenolate reaction. Overall, the review emphasizes the importance of NHCs in organocatalysis and their diverse applications in various chemical transformations.