Ligand‐controlled Regiodivergent C−H Alkenylation of Pyrazoles and its Application to the Synthesis of Indazoles

A one‐pot domino benzannulation protocol involving strapping of o‐chloropyrazolyl ynones with various nitromethane derivatives has been devised as a entry to diversely functionalized indazole frameworks. These preparatively useful transformations proceed via tandem Michael addition‐intramolecular SNAr reaction pathway to efficiently furnish a range of functionally enriched indazoles with bioactivity potential from readily accessible precursors.

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Zinc‐Catalyzed Asymmetric Formal [4+3] Annulation of Isoxazoles with Enynol Ethers by 6π Electrocyclization: Stereoselective Access to 2H‐Azepines

Zhu

Wang

Hou

et al. 2019

Angewandte Chemie

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6p electrocyclization has attracted interest in organic synthesis because of its high stereospecificity and atom economy in the construction of versatile 5-7-membered cycles. However,e xamples of asymmetric 6p electrocyclization are quite scarce,a nd have to rely on the use of chiral organocatalysts,a nd been limited to pentadienyl-anion-and trienetype 6p electrocyclizations.D escribed herein is az inc-catalyzed formal [4+ +3] annulation of isoxazoles with 3-en-1-ynol ethers via 6p electrocyclization, leading to the site-selective synthesis of functionalized 2H-azepines and 4H-azepines in good to excellent yields with broad substrate scope.Moreover, this strategy has also been used to produce chiral 2H-azepines with high enantioselectivities (up to 97:3 e.r.). This protocol not only is the first asymmetric heptatrienyl-cation-type 6p electrocyclization, but also is the first asymmetric reaction of isoxazoles with alkynes and the first asymmetric catalysis based on ynol ethers. Scheme 1. Asymmetric 6p electrocyclization.Supportinginformation and the ORCID identification number(s) for the author(s) of this article can be found under: https://doi.

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Ligand‐controlled Regiodivergent C−H Alkenylation of Pyrazoles and its Application to the Synthesis of Indazoles

Cited by 33 publications

References 53 publications

Functionalization of Five‐membered Heterocycles with Two Heteroatoms

Functionalization of Five‐membered Heterocycles with Two Heteroatoms

“Back‐to‐Front” Type Synthesis of Polyfunctionalized Indazoles: Nitromethane Mediated, Domino Benzannulation of o‐Chloropyrazolyl Ynones

Zinc‐Catalyzed Asymmetric Formal [4+3] Annulation of Isoxazoles with Enynol Ethers by 6π Electrocyclization: Stereoselective Access to 2H‐Azepines

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