Intra–Intermolecular Criss‐cross Cycloaddition of Nonsymmetrical Allenylazines with Fluorinated Enones as an Initial Step in the Synthesis of4<i>H</i>‐Pyrrolo[1,2‐<i>b</i>]pyrazoles

Man, Stanislav; Nečas, Marek; Bouillon, Jean‐Philippe; Portella, Charles; Potáček, Milan

doi:10.1002/ejoc.200600175

“…In another paper, the research team of Potáček, described a combined intra‐intermolecular CCC reaction of the non‐symmetrical homoallenylaldazine 174 with an another new type of interesting dipolarophile namely, perfluorinated enone 175 in boiling xylene with the expectation to achieve the three fused five membered ring systems 179 , but surprisingly!, they isolated new bicyclic adducts 176 along with minor amounts of the compounds 177 , except in the case of Ar= p ‐NO 2 C 6 H 4 , due to unpredictable fluoride anion migration and HF molecule elimination Scheme 25 [39f] . Moreover, similar to the earlier cases, herein, also they got the compound 183 while boiled in xylene without any dipolarophile.…”

Section: Introductionsupporting

confidence: 67%

The Criss‐Cross Cycloaddition: A Simple Access to Valuable Heterocycles and Polymers

Ali

¹

,

Hasan

²

2022

ChemistrySelect

1

0

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Aldazines are considered as the 2,3-diaza analogs of 1,4disubstituted-1,3-butadienes, and the addition takes place at the 1,3-and 2,4-positions instead of 1,4-or 1,2-positions of the conjugated double bonds to furnish the two fused fivemembered heterocyclic rings, and hence due to this peculiar reactivity pattern, in 1917, the reaction was dubbed as the "criss-cross" cycloaddition reaction by Bailey and co-workers -a special type of the [2 + 3]-cycloaddition, or 1,3-dipolar cycloaddition. Although, the reaction is known for more than a century, but still there are only countable reports available in the literature related to this wonderful cycloaddition reaction.Therefore, bearing the importance of this reaction in the generation of heterocyclic systems including polymeric materials in mind, we intended to comprehensively compile all the relevant data about this simple yet effective cycloaddition protocol. In this review article, we mainly categorized the whole document into four sections: intermolecular, intramolecular, combined inter-intramolecular and polymerization reactions. We are in the opinion that this particular review article would provide a seed for future advancements -cycloaddition in general and "criss-cross cycloaddition" in particular, and one can foresee a bright future for this still young area of research.

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“…The scarcity of uncharged dipole equivalents in the literature is likely a consequence of the unfavorable thermodynamic profile of the reaction. While pioneering work with azines demonstrated the potential of uncharged dipole equivalents to engage in [3+2] cycloadditions, [6n–v] the resulting ylide must be trapped by a subsequent cycloaddition reaction (Scheme 1 C). In contrast, our lab developed intermolecular [3+2] cycloadditions of imino‐isocyanates with alkenes to form stable cycloadducts, azomethine imines [6k] .…”

Section: Introductionmentioning

confidence: 99%

O‐Isocyanates as Uncharged 1,3‐Dipole Equivalents in [3+2] Cycloadditions

Beauchemin

¹

,

Ivanovich

²

,

Allen

³

2020

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1,3-Dipoles are commonly used in [3+ +2] cycloadditions,w hereas isoelectronic uncharged dipole variants remain underdeveloped. In contrast to conventional 1,3dipoles,unchargeddipole equivalents form zwitterionic cycloadducts,w hichc an be exploited to build further molecular complexity.I nt his work, the first cycloadditions of oxygensubstituted isocyanates (O-isocyanates) were studied experimentally and by DFT calculations.T his unique cycloaddition strategy provides access to an ovel class of heterocycle azaoxonium ylides through intramolecular and intermolecular cycloadditions with alkenes.This allowed asystematic study of the reactivity of the transient aza-oxonium ylide intermediate, which can undergo N À Obond cleavage followed by nitrene C À Hi nsertion, and the formation of b-lactams or isoxazolidinones upon varying the structure of the alkene or O-isocyanate reagents. Scheme 1. A) Conventionala nd unconventional [3+ +2] cycloadditions. B) Examples of uncharged 1,3-dipole equivalents. [6] C) Cycloaddition reactivity of azines, N-isocyanates, and alkoxyketenes. D) Potential cycloadditionr eactivity of O-isocyanates.

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O‐Isocyanates as Uncharged 1,3‐Dipole Equivalents in [3+2] Cycloadditions

Allen

¹

,

Ivanovich

²

,

Beauchemin

³

2020

View full text Add to dashboard Cite

1,3-Dipoles are commonly used in [3+ +2] cycloadditions,w hereas isoelectronic uncharged dipole variants remain underdeveloped. In contrast to conventional 1,3dipoles,unchargeddipole equivalents form zwitterionic cycloadducts,w hichc an be exploited to build further molecular complexity.I nt his work, the first cycloadditions of oxygensubstituted isocyanates (O-isocyanates) were studied experimentally and by DFT calculations.T his unique cycloaddition strategy provides access to an ovel class of heterocycle azaoxonium ylides through intramolecular and intermolecular cycloadditions with alkenes.This allowed asystematic study of the reactivity of the transient aza-oxonium ylide intermediate, which can undergo N À Obond cleavage followed by nitrene C À Hi nsertion, and the formation of b-lactams or isoxazolidinones upon varying the structure of the alkene or O-isocyanate reagents. Scheme 1. A) Conventionala nd unconventional [3+ +2] cycloadditions. B) Examples of uncharged 1,3-dipole equivalents. [6] C) Cycloaddition reactivity of azines, N-isocyanates, and alkoxyketenes. D) Potential cycloadditionr eactivity of O-isocyanates.

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Intra–Intermolecular Criss‐cross Cycloaddition of Nonsymmetrical Allenylazines with Fluorinated Enones as an Initial Step in the Synthesis of4H‐Pyrrolo[1,2‐b]pyrazoles

Cited by 10 publications

References 26 publications

The Criss‐Cross Cycloaddition: A Simple Access to Valuable Heterocycles and Polymers

The Criss‐Cross Cycloaddition: A Simple Access to Valuable Heterocycles and Polymers

O‐Isocyanates as Uncharged 1,3‐Dipole Equivalents in [3+2] Cycloadditions

O‐Isocyanates as Uncharged 1,3‐Dipole Equivalents in [3+2] Cycloadditions

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