A Practical Method for the Synthesis of Donor‐Acceptor Cyclobutanes by Cu(OAc)<sub>2</sub> or FeCl<sub>3</sub> Catalyzed [2+2] Cycloaddition

Domino Knoevenagel‐cyclization reactions of 2H‐chromene and chroman derivatives containing o‐formylaryl amine or ether side‐chain was carried out to produce four series of chiral condensed heterocycles representing four novel skeletons and exhibiting antiproliferative activity. The cyclization step occurred with four different mechanisms: a concerted intramolecular hetero Diels‐Alder reaction (IMHDA), a stepwise polar [2+2] cycloaddition, a [1,5]‐hydride shift‐6‐endo cyclization or a multi‐step nitro hetero Diels‐Alder‐ring‐opening‐Cadogan‐type cyclization sequence. The latter reaction provided a new route to hydroxyindoles by an inverse Cadogan‐type cyclization, in which the nitro group is deoxygenated by a nitro IMHDA‐ring‐opening sequence. The cyclization mechanisms and their stereoselectivity were studied by DFT calculations, based on which we proposed a mechanism for the multi‐step cyclization to hydroxyindoles and explained the observed diastereoselectivity.magnified image

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Multifaceted Domino Knoevenagel‐Cyclization Reactions; Four Movements for 2H‐Chromenes and Chromans

Király

Tóth

Kovács

et al. 2023

Adv Synth Catal

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Annulation via Ring Opening/Cyclization of Donor‐Acceptor Cyclobutanes with 2‐Naphthols: Access to Highly Functionalized Naphthalene‐Fused Oxepines

Wen,

Liu,

Chen

et al. 2023

Eur J Org Chem

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A mild and straightforward access to various substituted naphthalene‐fused oxepines from readily available Donor‐Acceptor (D‐A) cyclobutanes is reported. This method involves the Lewis acid‐catalyzed reactions of D‐A cyclobutanes with 2‐naphthols to afford ring‐opened products, which can undergo intramolecular cyclization mediated by the NBS‐base system to yield corresponding naphthalene‐fused oxepines. The cyclization protocol involves a nucleophilic attack of the oxygen of 2‐naphthol on the newly formed electrophilic acceptor end of D‐A cyclobutane.

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Fe(OTf)₃‐Catalyzed Cyanation of Isochromene Acetals with Trimethylsilyl Cyanide

Zhan

Hou

et al. 2021

ChemistrySelect

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An efficient Fe(OTf)3‐catalyzed nucleophilic addition of trimethylsilyl cyanide (TMSCN) to isochromene acetals has been achieved for the synthesis of 1‐cyano‐isochromenes. In the presence of 1–20 mol% Fe(OTf)3, a various of 1‐cyano‐isochromenes were obtained in good to excellent yields at room temperature. This transformation provides a simple and mild methodology for the synthesis of 1‐cyano‐isochromenes.

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A Practical Method for the Synthesis of Donor‐Acceptor Cyclobutanes by Cu(OAc)₂ or FeCl₃ Catalyzed [2+2] Cycloaddition

Abstract: Cu(OAc)2 or FeCl3 catalyzed [2+2] cycloaddition reaction between terminal alkenes and unpurified dialkyl methylidenemalonates was revealed. This new method represents a scalable and convenient approach for the transformation of alkenes into donor‐acceptor cyclobutanes.

Cited by 8 publications

References 51 publications

Multifaceted Domino Knoevenagel‐Cyclization Reactions; Four Movements for 2H‐Chromenes and Chromans

Multifaceted Domino Knoevenagel‐Cyclization Reactions; Four Movements for 2H‐Chromenes and Chromans

Annulation via Ring Opening/Cyclization of Donor‐Acceptor Cyclobutanes with 2‐Naphthols: Access to Highly Functionalized Naphthalene‐Fused Oxepines

Fe(OTf)₃‐Catalyzed Cyanation of Isochromene Acetals with Trimethylsilyl Cyanide

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A Practical Method for the Synthesis of Donor‐Acceptor Cyclobutanes by Cu(OAc)2 or FeCl3 Catalyzed [2+2] Cycloaddition

Abstract: Cu(OAc)2 or FeCl3 catalyzed [2+2] cycloaddition reaction between terminal alkenes and unpurified dialkyl methylidenemalonates was revealed. This new method represents a scalable and convenient approach for the transformation of alkenes into donor‐acceptor cyclobutanes.

Cited by 8 publications

References 51 publications

Multifaceted Domino Knoevenagel‐Cyclization Reactions; Four Movements for 2H‐Chromenes and Chromans

Multifaceted Domino Knoevenagel‐Cyclization Reactions; Four Movements for 2H‐Chromenes and Chromans

Annulation via Ring Opening/Cyclization of Donor‐Acceptor Cyclobutanes with 2‐Naphthols: Access to Highly Functionalized Naphthalene‐Fused Oxepines

Fe(OTf)3‐Catalyzed Cyanation of Isochromene Acetals with Trimethylsilyl Cyanide

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Product

Resources

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A Practical Method for the Synthesis of Donor‐Acceptor Cyclobutanes by Cu(OAc)₂ or FeCl₃ Catalyzed [2+2] Cycloaddition

Fe(OTf)₃‐Catalyzed Cyanation of Isochromene Acetals with Trimethylsilyl Cyanide