Uncatalyzed cationic olefin cyclizations of N-vinylic α-chloro-α-thioacetamides. Formation of β- and γ-lactams

Ishibashi, Hiroyuki; Nakaharu, Tohru; Nishimura, Masako; Nishikawa, A.; Kameoka, C.; Ikeda, Masazumi

doi:10.1016/0040-4020(95)00056-e

Cited by 12 publications

(5 citation statements)

References 14 publications

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“…This result is in striking contrast with a parallel transformation performed by the group starting from the N-phenylsuccinimide derivative 8, which gave the annulated product 9 in 65 % yield (Scheme 2). The p-methoxybenzyl group of imide 7a could be cleaved by treatment with Cerium(IV) ammonium nitrate (CAN) in the usual way [16] to give the corresponding deprotected imide 7f in 67 % yield.…”

Section: Resultsmentioning

confidence: 99%

Double Methylenecyclopentane Annulation of Succinimides: Easy Access to 3,7‐Dioxobicyclo[3.3.0]octane‐1,5‐dicarboximides

et al. 2009

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Keywords: Alkylation / Annulation / Carbocycles / Lithiation / Ozonolysis N-Alkylsuccinimides reacted with excess of LHMDS and 3-chloro-2-(chloromethyl)-1-propene to give in medium yields N-alkyl-3,7-dimethylenebicyclo[3.3.0]octane-1,5-dicarboximides, which were ozonized to the corresponding 3,7-dioxobicyclo[3.3.0]octane-1,5-dicarboximides. When these alkylations were carried out by using LDA as the base, cis-N-

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Section: Resultsmentioning

confidence: 99%

Double Methylenecyclopentane Annulation of Succinimides: Easy Access to 3,7‐Dioxobicyclo[3.3.0]octane‐1,5‐dicarboximides

et al. 2009

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“…Radical denitration with Bu 3 SnH in the presence of catalytic azobisisobutyronitrile (AIBN) provided the denitrated compound in 64 % yield. Subsequent treatment of the imide with ammonium hexanitratocerate(IV) (CAN)19 afforded ( S )‐(+)‐ethosuximide in 55 % yield. All spectroscopic and optical properties were found to be in good agreement with the literature 17c…”

Section: Resultsmentioning

confidence: 99%

Diphenylprolinol Silyl Ether Catalyzed Asymmetric Michael Reaction of Nitroalkanes and β,β‐Disubstituted α,β‐Unsaturated Aldehydes for the Construction of All‐Carbon Quaternary Stereogenic Centers

Hayashi¹,

Kawamoto²,

Honda³

et al. 2014

Chemistry A European J

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The asymmetric Michael reaction of nitroalkanes and β,β-disubstituted α,β-unsaturated aldehydes was catalyzed by diphenylprolinol silyl ether to afford 1,4-addition products with an all-carbon quaternary stereogenic center with excellent enantioselectivity. The reaction is general for β-substituents such as β-aryl and β-alkyl groups, and both nitromethane and nitroethane can be employed. The addition of nitroethane is considered a synthetic equivalent of the asymmetric Michael reaction of ethyl and acetyl substituents by means of radical denitration and Nef reaction, respectively. The short asymmetric synthesis of (S)-ethosuximide with a quaternary carbon center was accomplished by using the present asymmetric Michael reaction as the key step. The reaction mechanism that involves the E/Z isomerization of α,β-unsaturated aldehydes, the retro-Michael reaction, and the different reactivity between nitromethane and nitroethane is discussed.

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“…One example of a rearrangement of a very peculiar trisulfanylated β -lactam, i.e., 4-{bis(phenylsulfanyl)methylene}-1-(4-methoxybenzyl)-3-(methylsulfanyl)azetidin-2-one 4 toward the corresponding γ -lactam 5 via an intermediate N -acyliminium ion has been reported, but no information was given concerning the possibility and stereoselectivity of additions of nucleophiles at the N -acyliminium ion . In addition, the N -acyliminium ion was created by protonation of the exocyclic double bond at C4 of β -lactam 4 , implying that no information is present concerning the cation induced intramolecular rearrangement of β -lactams 2 toward N -acyliminium intermediates 3 in neutral or basic conditions (Scheme ).…”

Section: Introductionmentioning

confidence: 99%

Diastereoselective Ring Expansion of β-Lactams toward γ-Lactams via N-Acyliminium Intermediates

Brabandt

Kimpe

2005

J. Org. Chem.

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[reaction: see text] The diastereoselective synthesis of highly functionalized gamma-lactams starting from 4-(1-bromoalkyl)-2-azetidinones via N-acyliminium intermediates is described. The carbenium ions, formed by dissociation of bromide from 4-(1-bromoalkyl)-2-azetidinones in polar medium, are converted via a ring expansion toward N-acyliminium ions, which are susceptible to attack of oxygen, nitrogen, and carbon nucleophiles. In this way, a variety of 5-hydroxy-, 5-alkoxy, 5-cyano-, 5-allylamino- and 5-azido-4,4-dimethyl-2-pyrrolidinones were synthesized. It was found that dehydrobromination of 4-(1-bromoalkyl)-2-azetidinones constituted an important side reaction when the title reactions were carried out in DMSO. When THF was used as a solvent, generally no dehydrobromination was observed, implying that higher yields of gamma-lactams were obtained in THF compared to reactions performed in DMSO. Also substituents of the 4-(1-bromoalkyl)-2-azetidinones play an important role concerning the obtained diastereoselectivity and the degree of dehydrobromination.

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Uncatalyzed cationic olefin cyclizations of N-vinylic α-chloro-α-thioacetamides. Formation of β- and γ-lactams

Cited by 12 publications

References 14 publications

Double Methylenecyclopentane Annulation of Succinimides: Easy Access to 3,7‐Dioxobicyclo[3.3.0]octane‐1,5‐dicarboximides

Double Methylenecyclopentane Annulation of Succinimides: Easy Access to 3,7‐Dioxobicyclo[3.3.0]octane‐1,5‐dicarboximides

Diphenylprolinol Silyl Ether Catalyzed Asymmetric Michael Reaction of Nitroalkanes and β,β‐Disubstituted α,β‐Unsaturated Aldehydes for the Construction of All‐Carbon Quaternary Stereogenic Centers

Diastereoselective Ring Expansion of β-Lactams toward γ-Lactams via N-Acyliminium Intermediates

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