Directing-Group-Assisted Transition-Metal-Catalyzed Direct C–H Oxidative Annulation of Arenes with Alkynes for Facile Construction of Various Oxygen Heterocycles

Abstract

The most recent advances in the construction of oxygen heterocycles by the directing-group-assisted transition-metal-catalyzed direct oxidative annulation of arenes with diverse alkynes are summarized in this review. More than 140 recent research papers and many closely related reviews are referenced in this paper. Nine different oxygen heterocycles frameworks are discussed. Several traditional transition-metal catalysts as well as some classical non-noble metals are utilized to promote the annulation. Three plausible controlling models are disclosed to clarify the excellent regioselectivity outcomes achieved in case of unsymmetrical alkyne substrates.1 Introduction2 Coumarins3 I socoumarins and Their Analogues4 2-Pyrones and Their Analogues5 Chromones and Chroman-4-ones6 Chromenes and Isochromenes7 Fused Polycyclic Oxygen Heteroaromatics8 Benzofurans, Dihydrobenzofurans, and Furans9 Phthalides and Benzofuranones10 Benzoxepines11 Conclusion

Concise Synthesis of Isocoumarins through Rh-Catalyzed Direct Vinylene Annulation: Scope and Mechanistic Insight

“…Isocoumarins, also known as 1 H -2-benzopyrans or 3,4-benzopyrones, hold an important position due to their broad pharmacological applications, which include activities of antimicrobial, antifungal, anticancer, anti-HIV, anti-inflammatory, and so on. These facts prompted the synthetic community to establish efficient methods for the construction of isocoumarin scaffolds. , The past two decades witnessed a considerable advancement in transition-metal-catalyzed direct annulation of benzoic acids with unsaturated coupling partners through the activation of their ortho-C–H bond. , This protocol offers rapid access to the isocoumarins from readily available starting materials in a step-economical manner, and is practically beneficial as compared to the conventional acid- or electrophile-mediated cyclization of ortho-alkynylated benzoic acid derivatives (Scheme a,b). Coupling reactions with internal alkynes , have been extensively studied since our group reported the first direct annulation of benzoic acids adopting a Cp*Rh catalyst in 2007. , In addition, terminal alkenes and carbene precursors have also functioned as the coupling partners for the annulation of benzoic acid derivatives. , As a consequence, it is possible to design various 3-mono- and 3,4-disubstituted isocoumarins; however, the basic unit, i.e.…”

Construction of Vinyl‐SubstitutedN‐HeterocyclesviaRh(III)‐Catalyzed C−H Functionalization/Annulation of Pyrazolidinones

“…[7] Unsaturated coupling partners have been widely used in annulation reactions with phenyl via transitionmetal-catalyzed activation of phenyl orthoÀ CÀ H bonds in recent years. [8,9] However, most of the coupling partners are only suitable for 1,2-disubstituted acetylenes; this results in the products being composed of 1,2-disubstituted carbon-carbon double bonds. [10] Therefore, it is a crucial task to construct non-or mono-substituted heterocycles.…”

Chemo-, Regio-, and Stereoselective Assembly of Polysubstituted Furan-2(5H)-ones Enabled by Rh(III)-Catalyzed Domino C–H Alkenylation/Directing Group Migration/Lactonization: A Combined Experimental and Computational Study

“…Over the past two decades, transition-metal (TM)-catalyzed C–H functionalization with the assistance of heteroatom-based monodentate- and bidentate-directing groups (DGs) has emerged as one of the effective approaches for the synthesis of a variety of structurally diverse molecules because of its high efficiency in carbon–carbon/heteroatom bond construction without the prefunctionalization of starting materials . In principle, DG chelation-assisted ortho -metalation occurs at first in C–H functionalization to produce an active nucleophilic metallacycle intermediate, which then adds to various coupling partners (CPs) to afford the functionalized products (Scheme a) . Therefore, DGs are initially designed and employed as auxiliary groups, which help to improve regioselectivity as well as reactivity and in most cases simply remain at their original locations when reactions finish or in some cases undergo further intramolecular cyclization in situ .…”