1,3‐cycloaddition of nitrile oxide to olefinic fatty acid esters: synthesis of isoxazolines

Ahmed, Meraj; Mustafa, Jamal; Osman, S. M.

doi:10.1007/bf02660608

Cited by 6 publications

(4 citation statements)

References 12 publications

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“…We suspect the lower yields obtained using 6h relative to 6g result from the difficulty in handling the hygroscopic reagent. The chemical shifts and coupling constants determined from 1 H NMR analyses of purified isoxazoline 4h are similar to those reported by Ahmed et al (16) and to the other isoxazoline ring hydrogens reported in this work (Table 1). Additionally, the chemical shift, splitting patterns, and coupling constant values for the isoxazoline ring hydrogens of 5h would be substantially different from what was observed.…”

supporting

confidence: 89%

“…As can be seen from Table 1 (entries 4g and 4h), in our hands, the isoxazoline yields obtained from these reactions were somewhat lower than those reported by Ahmed et al (16), 66% and 55% for 4g and 4h, respectively. We suspect the lower yields obtained using 6h relative to 6g result from the difficulty in handling the hygroscopic reagent.…”

contrasting

confidence: 76%

“…Ahmed et al (16). Interestingly, they reported the 1,3-cycloaddition between methyl 10-undecenoate and nitrile oxide MeOOCC≡N + -O − , obtained from the reaction of methyl chlorooximidoacetate with base, gave the 3,4-substituted regioisomer exclusively in 90% yield.…”

mentioning

confidence: 99%

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Synthesis of Δ²‐Isoxazoline fatty acid ester heterocycles

Kenar

Erhan

2001

J Americ Oil Chem Soc

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Fatty ester ∆ 2 -isoxazoline heterocycles were prepared in good yields and excellent regioselectivity from 1,3-dipolar cycloaddition reactions between methyl 10-undecenoate and nitrile oxides. This methodology provides convenient access to the methyl esters of margaric (4b) and stearic (4c) acids in 63-66% yield that contain the isoxazoline heterocycle between C-10 and C-12. These fatty heterocycle compounds are synthesized in a one-pot sequence in which methyl 10-undecenoate is used to trap the reactive nitrile oxide intermediates that are generated by reacting aldoximes with aqueous sodium hypochlorite and a catalytic amount of triethylamine or by directly reacting hydroximic acid chlorides with a stoichiometric amount of base. The fatty ester ∆ 2 -isoxazoline heterocycles represent a versatile synthon that may be useful to obtain oleochemicals with potentially new and interesting properties not easily accessible by other methods.The 1,3-dipolar cycloaddition reaction between nitrile oxides and alkenes has been known for many years, and it provides convenient access to the complex five-membered heterocyclic ring system known as isoxazolines (1, an excellent review of nitrile oxide chemistry). Recently, interest in ∆ 2 -isoxazolines has increased markedly because of reports describing their pharmacological properties (2,3) and because ∆ 2 -isoxazolines represent a synthetically versatile intermediate that readily undergoes further transformations, e.g., alkylation (4), dehydrogenation to isoxazoles (5), or reductive cleavage to expose functionality such as β-hydroxy ketones, α,β-unsaturated ketones (6), or γ-amino alcohols (7).Because nitrile oxides are highly reactive intermediates and dimerize readily to furoxans, they are usually generated in situ and trapped in the presence of olefinic substrates. The two most widely used routes to prepare isoxazolines by trapping nitrile oxides with alkenes are: (i) the Mukaiyama (8) method (or a variation thereof) in which primary nitroalkanes are reacted with a dehydrating agent such as aryl isocyanates and (ii) dehydrohalogenation of hydroximic acid chlorides obtained by reacting aldoximes with a halogenating agent such as N-chlorosuccinimide (9) or chlorine (10). The aldoxime route is a convenient method to generate nitrile oxides to be trapped by olefins, and recently a simple procedure was reported in which water-insoluble aldoximes are reacted with sodium hypochlorite (household bleach) under biphasic conditions (11). This methodology represents a practical entry into ∆ 2 -isoxazolines because the starting materials needed are generally inexpensive and readily available, and importantly, the simplicity of the reaction allows it to be readily scaled up.The straightforward synthesis of ∆ 2 -isoxazolines from nitrile oxides and their potentially interesting properties coupled with their synthetic versatility make them an interesting class of compounds that have potential industrial or biological applications. Herein, we now report an initial study focused on the synthes...

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confidence: 89%

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confidence: 76%

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Synthesis of Δ²‐Isoxazoline fatty acid ester heterocycles

Kenar

Erhan

2001

J Americ Oil Chem Soc

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“…The desired product, 5-(Carbomethoxyheptyl)-4-octyl-3-propyl-4,5dihydroisoxazole ( 5), was obtained with a very good yield of 85% (Scheme 3). Osman and the team [9] conducted studies on the [3+2] cycloaddition of methoxycarbonylformonitrile N-oxide (6), including with methyl oleate (2). The N-oxide was generated in situ, and the reaction was carried out in diethyl ether.…”

Section: Oleic Acid and Its Esters As Components Of The [3+2] Cycload...mentioning

confidence: 99%

The Participation of Oleic Acid and its Esters in [3+2] Cycloaddition Reactions: A Mini-Review

Dresler

2024

Sci. Rad.

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This mini review presents the state of knowledge on the [3+2] cycloaddition reactions involving fatty acids and their esters with triatomic components (TAC). In general, the literature reports are quite sparse and relatively old. The reaction yield was in the range of 12-85%. The best result of 32CA was obtained from the reaction of butylonitrile N-oxide (4) and methyl oleate (2). Other tested TAC as components of title reactions were nitrylimines and ozone.

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