Reactions of Phenyltriazolinedione with Alkenes. Stereochemistry of Methanol Adducts to Aziridinium Imide Intermediates

The reaction of N‐phthaloyl‐L‐leucine acid chloride (1) with isoeugenol (2) was carried out in chloroform, and novel optically active isoeugenol ester derivative 3 as a chiral monomer was obtained in high yield. Compound 3 was characterized by 1H‐NMR, IR, and mass and elemental analysis and then was used for the preparation of model compound 5 and polymerization reactions. 4‐Phenyl‐1,2,4‐triazoline‐3,5‐dione, PhTD (4), was allowed to react with compound 3. The reaction is very fast and gives only one diastereomer of 5 via Diels–Alder and ene pathways in quantitative yield. In order to explain this diastereoselectivity, a nonconcerted two‐step mechanism involving benzylic cation (BC) and aziridinium (AI) have been proposed for the Diels–Alder and ene reactions, respectively. The polymerization reactions of novel monomer 3 with bis(triazolinedione)s [bis(p‐3,5‐dioxo‐1,2,4‐triazolin‐4‐ylphenyl)methane (8) and 1,6‐bis(3,5‐dioxo‐1,2,4‐triazolin‐4‐yl)hexane] (9)] were performed in N,N‐dimethylacetamide (DMAc) at room temperature. The reactions are exothermic, fast, and gave novel optically active polymers 10 and 11 via repetitive Diels–Alder–ene polyaddition reactions. These polymers have inherent viscosities in a range about 0.18–0.22 dL/g. Some physical properties and structural characterizations of these new polymers have been studied and are reported. © 1999 John Wiley & Sons, Inc. J Polym Sci A: Polym Chem 37: 1211–1219, 1999

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“…Smonou and co-workers 36 have studied the ene reaction of PhTD with alkenes. They proposed AI as an intermediate.…”

Section: Resultsmentioning

confidence: 99%

Asymmetric polymerization via cycloaddition reactions

Mallakpour

Hajipour

Mahdavian

et al. 1999

J. Polym. Sci. A Polym. Chem.

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“…The ylide 5 (Scheme 2) required for the Wittig reaction with 4 was synthesised according to the literature procedure from commercially available triphenylphosphane and methyl 2-bromopropionate in the presence of triethyl-amine. [14] A solution of the aldehyde 4 in dichloromethane was added dropwise to a solution of the ylide 5 in dichloromethane (Scheme 2). The reaction mixture was stirred overnight at room temperature under an inert atmosphere, after which time TLC analysis of the mixture indicated complete consumption of the starting material along with the formation of a new component.…”

Section: Resultsmentioning

confidence: 99%

Towards the Total Synthesis of Mycaperoxide B: Probing Biosynthetic Rationale

et al. 2011

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“…[27] To rationalize the formation of only one stereoisomer, a rather tight AI intermediate that does not equilibrate to any significant extent with a zwitterionic intermediate has been proposed. The loss of stereochemical integrity observed in the case of methyl-substituted indene (13; Scheme 8) was attributed to the fact that this AI intermediate can yield a highly stable, tertiary benzylic carbocation.…”

Section: Discussionmentioning

confidence: 99%

“…It was therefore concluded that the stability of the AI intermediate and its equilibration with the open intermediate depends on the particular system. [27] (14), and 2-methyl-2-butene (15).…”

Section: Discussionmentioning

confidence: 99%

“…[27] Finally, in the intermolecular competition between [D 12 ]TME and [D 0 ]TME, the absence of a KIE when the reaction is carried out in CH 2 Cl 2 ( Table 3, entries 1 and 2) demonstrates that once the aziridinium imide or/and open intermediate is formed, only one kind of isotope (either H or D, non-competing) is available for abstraction in an irreversible mode. In contrast to the hitherto accepted mechanism for the ene reaction of RTADs, the KIEs observed in MeOH (Table 3, entries 3 and 4) again suggest reversible generation of the aziridinium imide.…”

Section: Wwwchemeurjorgmentioning

confidence: 97%

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Solvent‐Dependent Changes in the Triazolinedione–Alkene Ene Reaction Mechanism

Vougioukalakis

Roubelakis

Alberti

et al. 2008

Chemistry A European J

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The influence of the solvent on the triazolinedione-alkene ene reaction mechanism has been investigated. Both inter- and intramolecular kinetic isotope effects with tetramethylethylenes and 2,2,2-(trideuterio)methyl-7-methyl-2,6-octadiene-[D3]-1,1,1 provide, for the first time, strong evidence for changes in the mechanism of the reaction on going from non-protic to polar protic solvents. In non-protic polar or apolar solvents, an aziridinium imide that equilibrates to an insignificant extent with an open intermediate (a dipolar or a polarized biradical) is formed irreversibly in the first, rate-determining step of the reaction, which is followed by fast hydrogen abstraction. On the contrary, in polar protic solvents, hydrogen abstraction is rate limiting, allowing the main dipolar intermediate to equilibrate with its open intermediate(s) as well as with the starting reagents.

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Reactions of Phenyltriazolinedione with Alkenes. Stereochemistry of Methanol Adducts to Aziridinium Imide Intermediates

Cited by 35 publications

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Asymmetric polymerization via cycloaddition reactions

Asymmetric polymerization via cycloaddition reactions

Towards the Total Synthesis of Mycaperoxide B: Probing Biosynthetic Rationale

Solvent‐Dependent Changes in the Triazolinedione–Alkene Ene Reaction Mechanism

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