Enantioselective Organocatalytic Four‐Atom Ring Expansion of Cyclobutanones: Synthesis of Benzazocinones

Zhou, Yirong; Wei, Yuanyuan; Rodríguez, Jean; Coquerel, Yoann

doi:10.1002/ange.201810184

Angewandte Chemie

2018

DOI: 10.1002/ange.201810184

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Enantioselective Organocatalytic Four‐Atom Ring Expansion of Cyclobutanones: Synthesis of Benzazocinones

Yirong Zhou

Yuanyuan Wei

Jean Rodríguez

et al.

Abstract: An enantioselective Michael addition-four-atom ring expansion cascade reaction involving cyclobutanones activated by a N-aryl secondary amide group and ortho-amino nitrostyrenes has been developed for the preparation of functionalized eight-membered benzolactams using bifunctional aminocatalysts. Taking advantage of the secondary amide activating group, the eight-membered cyclic products could be further rearranged into their six-membered isomers having a glutarimide core under base catalysis conditions withou… Show more

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Cited by 18 publications

References 70 publications

(9 reference statements)

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Synthesis of Eight‐Membered Lactams through Formal [6+2] Cyclization of Siloxy Alkynes and Vinylazetidines

Feng

Sung

et al. 2019

Angewandte Chemie

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An ew approachf or the efficient synthesis of eightmembered lactams through formal [6+ +2] cyclization of siloxy alkynes and vinylazetidines has been developed. Evidence from ac hirality transfer experiment suggests that the reaction proceeds via a[3,3]-sigmatropic rearrangement from aketene intermediate.This insight led to the development of alternative conditions and use of acyl chlorides as ketene precursors for the [6+ +2] reaction with vinylazetidines.

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Synthesis of Eight‐Membered Lactams through Formal [6+2] Cyclization of Siloxy Alkynes and Vinylazetidines

Feng

Sung

et al. 2019

Angewandte Chemie

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Internal Nucleophilic Catalyst Mediated Cyclisation/Ring Expansion Cascades for the Synthesis of Medium‐Sized Lactones and Lactams

et al. 2019

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Astrategy for the synthesis of medium-sized lactones and lactams from linear precursors is described in whicha n amine acts as an internal nucleophilic catalyst to facilitate an ovel cyclisation/ring expansion cascade sequence.T his method obviates the need for the high-dilution conditions usually associated with medium-ring cyclisation protocols,a s the reactions operate exclusively via kinetically favourable "normal"-sized cyclic transition states.T his same feature also enables biaryl-containing medium-sized rings to be prepared with complete atroposelectivity by point-to-axial chirality transfer.

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Stereoselective Access to Polyfunctionalized Nine‐Membered Heterocycles by Sequential Gold and Palladium Catalysis

Yang

Zhao

2021

Angewandte Chemie

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We report herein a gold and palladium sequential catalysis system to access furan-fused nine-membered heterocycles in high efficiency and enantioselectivity. In this one-pot procedure, easily accessible enynamides undergo cyclization to generate azadienes in situ that participate in enantioselective formal [5+4] cycloaddition with vinyl ethylene carbonates. Conformation-controlled highly diastereoselective derivatizations of these medium-sized rings, coupled with oxidative furan cleavage, have enabled the access to diverse densely-functionalized nine-membered lactams.Medium-sized heterocycles (8 to 11-membered rings) are important structural motifs in various bioactive natural products. [1] The synthesis of these medium-sized rings, however, still remains a great challenge for catalytic method development. Out of the different synthetic strategies developed for medium-sized ring formation, intramolecular cyclization or ring expansion is most explored. [2,3] As an alternative and synthetically flexible approach, intermolecular dipolar cycloaddition provides a significant advantage of directly coupling two building blocks (serving as dipoles and dipolarophiles) to produce medium-sized heterocycles. [4] However, success along these lines remains limited, with cycloaddition of only a few classes of 1,4-dipolarophiles reported in the literature. Our group has introduced a dihydrobenzofuran-derived azadiene [5] to realize highly stereoselective Pd-catalyzed cycloadditions for the preparation of nine-or ten-membered benzofuran/indole-fused heterocycles. [5b-d] The same substrate was also used by the Lu group to achieve phosphine-catalyzed enantioselective eight-membered heterocycle synthesis. [6] The Shibata group has introduced CF 3 -substituted benzooxazinones for Pd-catalyzed decarboxylative cycloaddition to access benzo-fused nine-or twelve-membered heterocycles. [7] The formal [5+4] cycloaddition using ortho-quinone methides to access enantioenriched benzo-fused nine-membered rings have also been reported by the Fan group and the Guo group. [8] Despite these advances, it is important to note that due to the special Scheme 1. Diverse nine-membered heterocycles prepared from in situ generated azadienes.

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Enantioselective Organocatalytic Four‐Atom Ring Expansion of Cyclobutanones: Synthesis of Benzazocinones

Cited by 18 publications

References 70 publications

Synthesis of Eight‐Membered Lactams through Formal [6+2] Cyclization of Siloxy Alkynes and Vinylazetidines

Synthesis of Eight‐Membered Lactams through Formal [6+2] Cyclization of Siloxy Alkynes and Vinylazetidines

Internal Nucleophilic Catalyst Mediated Cyclisation/Ring Expansion Cascades for the Synthesis of Medium‐Sized Lactones and Lactams

Stereoselective Access to Polyfunctionalized Nine‐Membered Heterocycles by Sequential Gold and Palladium Catalysis

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