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1,2,3,4-Tetrahydroquinolines (THQs) are present in molecules with significant biological importance and pharmaceuticals with diverse biological activities. Various synthetic routes have been developed to tetrahydroquinolines, such as the hydrogenation of quinolines, domino reactions, intramolecular cyclization, and notably, the Povarov reaction. Organocatalysts are small, chiral organic molecules that can successfully catalyze organic transformations. This review examines the use of organocatalysts in the asymmetric synthesis of tetrahydroquinoline derivatives using aminocatalysis, NHC catalysis, and H-bonding catalysis covering the literature between 2000 and early 2024. 1 Introduction 2 Aminocatalysis 3 NHC Catalysis 4 H-Bonding Catalysis 5 Miscellaneous 6 Conclusion [ABSTRACT FROM AUTHOR]

This review highlights the multifaceted usefulness of o -halobenzyl halides as pivotal substrates for the construction of five- to nine-membered cyclic structures with the aid of transition metals as catalysts. These privileged entities engage dual active sites, enabling the combination of both intermolecular benzylation and intramolecular arylation strategies that directs the formation of a diverse repository of cyclic structures. The introduction of transition-metal catalysis in cross-coupling transformations sparked a revolution in forging aryl–heteroatom bonds, culminating in the evolution of more potent methodologies for the synthesis of a wide spectrum of valuable compounds. Furthermore, the associated pharmaceutical and biological attributes of these cyclic structures augment their significance in medicinal chemistry research. This review aims to showcase the importance of this synthetic methodology and its far-reaching applications in synthesis. 1 Introduction 2 Synthesis of Five-Membered Rings 3 Synthesis of Six-Membered Rings 4 Synthesis of Seven-Membered Rings 5 Synthesis of Eight- and Nine-Membered Rings 6 Conclusion [ABSTRACT FROM AUTHOR]

The synthesis of 1,3-enyne has widespread appeal in organic synthesis due to their proven adaptability as intermediates in routes to compounds of significant biological and material interest. A variety of methods have been designed to formulate 1,3-enynes from diverse substrates, such as alkynes, 1,3-diynes, alkynyl-substituted cyclopropanes, and propargyl alcohols. This review covers the synthesis of 1,3-enynes utilizing the homo- and cross-coupling of alkynes, nucleophilic metal/acid-induced cyclopropane ring opening, and rearrangement/dehydration of propargyl alcohols. A key concern in procedures starting from alkynes and 1,3-diynes is the management of regio-, stereo-, and, where fitting, chemoselectivity. In contrast, in cyclopropyl ring opening nucleophile orientation determines the 1,3-enynes formed. Efficient methods for the broad and selective synthesis of 1,3-enynes are highlighted and specific examples are given to demonstrate the efficacy of these processes. 1 Introduction and Scope 2 Synthesis 2.1 Synthesis of 1,3-Enynes from Alkynes 2.1.1 Metal-Catalyzed Cross-Coupling/Additions of Alkynes with Alkenes or Vinyl or Aryl Halides 2.1.1.1 Palladium Catalysis 2.1.1.2 Rhodium Catalysis 2.1.1.3 Copper Catalysis 2.1.1.4 I ron Catalysis 2.1.1.5 Nickel Catalysis 2.1.1.6 Miscellaneous 2.2 Synthesis of Enynes from Propargyl Alcohols 2.3 Metal/Acid-Catalyzed Ring Opening of Cyclopropanes 3 Conclusion [ABSTRACT FROM AUTHOR]

The reductive cyclization of o-nitrobenzylidene amines under microwave conditions employing MoO2Cl2(dmf)2 as catalyst and Ph3P as reducing agent delivers 2-aryl-2H-indazoles with yields ranging from 61-92%. [ABSTRACT FROM AUTHOR]