Seven-Membered Rings

Meyer, Adam G.; Bissember, Alex C.; Hyland, Christopher J. T.; Williams, Charlotte C.; Szabó, Mónika; Pearsall, Melanie A.; Hyland, Isabel K.; Olivier, Wesley J.

doi:10.1016/b978-0-12-819962-6.00016-6

Cited by 9 publications

(8 citation statements)

References 310 publications

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“…However, a rapid procedural optimization provided more consistent yields. Indeed, heating the sample at 70 °C for 2 h ensured a complete conversion of 12e and clean formation of azepane 14c (68%) which upon further treatment with 2 M HCl in dioxane afforded hydrochloride 15a ·HCl, whose melting point (mp = 174–175 °C, lit . = 167–168 °C) and spectral data matched the reported literature values.…”

Section: Resultssupporting

confidence: 79%

“…For a successful synthesis of 3 , we sought to reverse the reaction sequence by the prior formation of the azepane ring. Scrutinizing the literature, data revealed that cyclization reactions of acyclic precursors have rarely been employed for the synthesis of monocyclic azepine derivatives . For example, the synthesis of 2-propylazepane 14c has been carried out through the reductive alkylation of N -benzylcaprolactam or from the addition of Grignard reagents on preformed enamine–zinc complexes .…”

Section: Resultsmentioning

confidence: 99%

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Alkylation of N,N-Dibenzylaminoacetonitrile: From Five- to Seven-Membered Nitrogen-Containing Heterocyclic Systems

et al. 2023

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The syntheses of several alkaloids and nitrogen-containing compounds including N-Boc-coniine (14b), pyrrolizidine (1), δ-coniceine (2), and pyrrolo[1,2a]azepine (3) are described. New C–C bonds in the α position relative to the nitrogen atom were formed by the alkylation of metalated α-aminonitriles 4 and 6a–c with alkyl iodides possessing the requisite size and functionality. In all of the reported cases, the pyrrolidine ring was formed in the aqueous medium through a favorable 5-exo-tet process involving a primary or a secondary amino group and a terminal δ-leaving group. Conversely, the azepane ring was efficiently formed in N,N-dimethylformamide (DMF), as the preferred aprotic solvent, through an unreported 7-exo-tet cyclization process involving a more nucleophilic sodium amide and a terminal mesylate borne by a saturated six carbon chain unit. In this way, we successfully synthesized pyrrolo[1,2a]azepane 3 and 2-propyl-azepane 14c in good yields from inexpensive and readily available materials without tedious separation methods.

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Section: Resultssupporting

confidence: 79%

Section: Resultsmentioning

confidence: 99%

Alkylation of N,N-Dibenzylaminoacetonitrile: From Five- to Seven-Membered Nitrogen-Containing Heterocyclic Systems

et al. 2023

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“…Thereby, direct construction of 7-membered ring via C7–H cyclization of benzoimidazoles with alkenes would provide a more straightforward, atom- and step-economical access to tricyclic imidazoles from more easily-accessible substrates. However, transition metal-catalyzed C–H cyclization for medium-ring synthesis has been a challenging goal during the past two decades 16 , 17 . Early efforts focused on the cyclization of reactive formyl C–H bonds with alkenes via rhodium catalysis 18 – 28 .…”

Section: Introductionmentioning

confidence: 99%

Construction 7-membered ring via Ni–Al bimetal-enabled C–H cyclization for synthesis of tricyclic imidazoles

Wang

et al. 2021

Nat Commun

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The construction of 7-membered ring via direct C7–H cyclization of benzoimidazoles with alkenes would provide a more atom- and step-economical route to tricyclic imidazoles and derivatives that widely exist in a broad range of bioactive molecules. However, transition metal-catalyzed C–H cyclization for medium-ring synthesis has been limited to reactive C–H bonds, instead, the activation of unreactive C–H bonds towards medium synthesis still remains an elusive challenge. Herein, we report a direct construction of 7-membered rings via Ni–Al co-catalyzed unreactive C7–H cyclization of benzoimidazoles with alkenes, providing a series of tricyclic imidazoles in 40–98% yield and with up to 95:5 er.

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“…On the other hand, transition metal-catalyzed C−H cyclization for medium-ring synthesis has become an important endeavor and attracted considerable interests during the past two decades, 16,17 because such methods can not only allow using more readily available starting materials, but also provide more atomand step-economical routes ( Fig. 2a).…”

Section: Introductionmentioning

confidence: 99%

Construction 7-Membered Ring via Ni-Al Bimetal-Enabled C-H Cyclization for Synthesis of Tricyclic Imidazoles

et al. 2021

Preprint

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The construction of 7-membered ring via direct C7−H cyclization of benzoimidazoles with alkenes would provide a more atom- and step economical route to tricyclic imidazoles and derivatives that widely exist in a broad range of bioactive molecules. However, transition metal-catalyzed C−H cyclization for medium-ring synthesis has been limited to reactive C−H bonds, instead, the activation of unreactive C−H bonds towards medium synthesis still remains an elusive challenge. Herein, we report a direct construction of 7-membered rings via Ni−Al co-catalyzed unreactive C7−H cyclization of benzoimidazoles with alkenes, providing a series of tricyclic imidazoles in 40−98% yield and with up to 95:5 er.

show abstract

Seven-Membered Rings

Cited by 9 publications

References 310 publications

Alkylation of N,N-Dibenzylaminoacetonitrile: From Five- to Seven-Membered Nitrogen-Containing Heterocyclic Systems

Alkylation of N,N-Dibenzylaminoacetonitrile: From Five- to Seven-Membered Nitrogen-Containing Heterocyclic Systems

Construction 7-membered ring via Ni–Al bimetal-enabled C–H cyclization for synthesis of tricyclic imidazoles

Construction 7-Membered Ring via Ni-Al Bimetal-Enabled C-H Cyclization for Synthesis of Tricyclic Imidazoles

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