Carbocyclization Cascades of Allyl Ketenimines viaAza-Claisen Rearrangements ofN-Phosphoryl-N-allyl-ynamides

DeKorver, Kyle A.; Wang, Xiaona; Walton, Mary C.; Hsung, Richard P.

doi:10.1021/ol300366e

Cited by 45 publications

(25 citation statements)

References 51 publications

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“…In suitably substituted N -phosphoryl ynamides, we demonstrated that N -promoted Meerwein-Wagner alkyl shifts could compete with the 1,2- H shift leading to fused or spiro bicyclic products. 10 In addition to exploiting the zwitter ionic intermediates via N -promoted ring expansions and contractions, we envisioned the possibility of intercepting 19 the intermediates with tethered nucleophiles to prepare a variety of bicyclic scaffolds such as 43a – 43c [Scheme 8]. …”

Section: Resultsmentioning

confidence: 99%

“…1–3 In our own effort during the past several years, we have been heavily interested in using Pd-catalyzed and thermal aza -Claisen 4,5 rearrangements as a means of activating N -allyl ynamides towards (1) nucleophilic additions of amines 6 and alcohols, 7 (2) inter- 8 and intramolecular 9 [2 + 2] cycloaddition reactions, (3) skeletal rearrangements yielding nitriles, 6c and (4) carbocyclizations 10 and cationic polyene cascades.…”

Section: Introductionmentioning

confidence: 99%

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Synthesis of Cyclopentenimines from N-Allyl Ynamides via a Tandem Aza-Claisen Rearrangement–Carbocyclization Sequence

et al. 2013

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We describe here details of our investigations into Pd-catalyzed and thermal aza-Claisen–carbocyclizations of N-allyl ynamides to prepare a variety of α,β-unsaturated cyclopentenimines. The nature of the ynamide electron withdrawing group and β-substituent plays critical roles in the success of this tandem cascade. With N-sulfonyl ynamides, the use of palladium catalysis is required, as facile 1,3-sulfonyl shifts dominate under thermal conditions. However, since no analogous 1,3-phosphoryl shift is operational, N-phosphoryl ynamides could be used to prepare similar cyclopentenimines under thermal conditions through zwitter ionic intermediates that undergo N-promoted H-shifts. Alternatively, by employing ynamides bearing tethered carbon nucleophiles, the zwitter ionic intermediates could be intercepted giving rise rapidly to more complex fused bi- and tricyclic scaffolds.

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Section: Resultsmentioning

confidence: 99%

Section: Introductionmentioning

confidence: 99%

Synthesis of Cyclopentenimines from N-Allyl Ynamides via a Tandem Aza-Claisen Rearrangement–Carbocyclization Sequence

et al. 2013

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“…DeKorver and Hsung 70 showcased a tandem aza- Claisencarbocyclization of N -phosphoryl- N -allyl-ynamides that included possibilities such as ring-expansion via Meerwein-Wagner rearrangement and polyene-type cyclizations, thereby rapidly building structural complexity leading to fused bi- and tricyclic scaffolds (Scheme 61). …”

Section: Rearrangementsmentioning

confidence: 99%

Ynamides in Ring Forming Transformations

et al. 2013

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Conspectus The ynamide functional group activates carbon-carbon triple bonds through an attached nitrogen atom that bears an electron-withdrawing group. As a result, the alkyne has both electrophilic and nucleophilic properties. Through the selection of the electron-withdrawing group attached to nitrogen chemists can modulate the electronic properties and reactivity of ynamides, making these groups versatile synthetic building blocks. The reactions of ynamides also lead directly to nitrogen-containing products, which provides access to important structural motifs found in natural products and molecules of medicinal interest. Therefore, researchers have invested increasing time and research in the chemistry of ynamides in recent years. This Account surveys and assesses new organic transformations involving ynamides developed in our laboratory and in others around the world. We showcase the synthetic power of ynamides for rapid assembly of complex molecular structures. Among the recent reports of ynamide transformations, ring-forming reactions provide a powerful tool for generating molecular complexity quickly. In addition to their synthetic utility, such reactions are mechanistically interesting. Therefore, we focus primarily on the cyclization chemistry of ynamides. This Account highlights ynamide reactions that are useful in the rapid synthesis of cyclic and polycyclic structural manifolds. We discuss the mechanisms active in the ring formations and describe representative examples that demonstrate the scope of these reactions and provide mechanistic insights. In this discussion we feature examples of ynamide reactions involving radical cyclizations, ring-closing metathesis, transition metal and non-transition metal mediated cyclizations, cycloaddition reactions, and rearrangements. The transformations presented rapidly introduce structural complexity and include nitrogen within, or in close proximity to, a newly formed ring (or rings). Thus, ynamides have emerged as powerful synthons for nitrogen-containing heterocycles and nitrogen-substituted rings, and we hope this Account will promote continued interest in the chemistry of ynamides.

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“…[10] First, it was demonstrated that ketenimine 16 was sufficiently electrophilict hat ac arbocyclization to cyclopentenyl zwitterion 17 could take place (Scheme 8). [10] First, it was demonstrated that ketenimine 16 was sufficiently electrophilict hat ac arbocyclization to cyclopentenyl zwitterion 17 could take place (Scheme 8).…”

Section: Thermal Rearrangementsmentioning

confidence: 99%

Ketenimines Generated from Ynamides: Versatile Building Blocks for Nitrogen‐Containing Scaffolds

Dodd

Cariou

2017

Chemistry A European J

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Using ynamides as readily available starting materials, a single step can generate highly reactive ketenimines, which can then undergo a variety of transformations. The choice of the method for generating the ketenimine dictates the outcome of the reaction that can, moreover, be precisely steered through minor variations of the starting material. This Concept gives an overview of the different existing methodologies for this objective, showcasing the diverse nitrogen-containing frameworks that can be obtained by this highly versatile strategy.

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Carbocyclization Cascades of Allyl Ketenimines viaAza-Claisen Rearrangements ofN-Phosphoryl-N-allyl-ynamides

Cited by 45 publications

References 51 publications

Synthesis of Cyclopentenimines from N-Allyl Ynamides via a Tandem Aza-Claisen Rearrangement–Carbocyclization Sequence

Synthesis of Cyclopentenimines from N-Allyl Ynamides via a Tandem Aza-Claisen Rearrangement–Carbocyclization Sequence

Ynamides in Ring Forming Transformations

Ketenimines Generated from Ynamides: Versatile Building Blocks for Nitrogen‐Containing Scaffolds

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