Intermolecular and Selective Synthesis of 2,4,5‐Trisubstituted Oxazoles by a Gold‐Catalyzed Formal [3+2] Cycloaddition

Davies, Paul W.; Cremonesi, Alex; Dumitrescu, Lidia

doi:10.1002/ange.201103563

Cited by 92 publications

(22 citation statements)

References 95 publications

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“…Davies 48 reported that 2,4,5-trisubstituted oxazoles 211 could be synthesized from ynamides 210 and 1,3- N , O- dipole equivalents 209 in a gold (III) catalyzed process (Scheme 40). …”

Section: Cycloadditions and Formal Cycloadditionsmentioning

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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“…Davies 48 reported that 2,4,5-trisubstituted oxazoles 211 could be synthesized from ynamides 210 and 1,3- N , O- dipole equivalents 209 in a gold (III) catalyzed process (Scheme 40). …”

Section: Cycloadditions and Formal Cycloadditionsmentioning

confidence: 99%

Ynamides in Ring Forming Transformations

et al. 2013

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“…[10] Due to the p-acid and electron-donor dual reactivity of gold catalysts, alkynes can be used as precursor of a gold carbenoid, albeit with several exceptions. [11] Leaving group-bearing nucleophiles such as sulfoxide, [12] pyridine/quinoline N-oxide, [13] nitrone, [14] nitro, [15] azide, [16] pyridine N-aminide, [17] sulfur ylide, [18] epoxide [19] and iminopyridium ylide [20] can be used to obtain a carbene intermediate. Many unconventional and efficient transformations to access molecules which are not easily available through traditional organic reactions have been realized.…”

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confidence: 99%

Synthesis of Cyclobutanones via Gold‐Catalyzed Oxidative Rearrangement of Homopropargylic Ethers

Ren

Wang

et al. 2013

Adv Synth Catal

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“…Other new reactions with alkynes have also been described by combining iminopyridinium ylides with gold catalysts, which leads to the production of either amidines or oxazoles. [52] However, as fairly concluded by the Davies group, these reactions rather involve nitrene equivalents. Addition of the ylides onto gold-activated alkynes followed by elimination of the neutral pyridine ring leads to a-imino gold carbene intermediates that are otherwise difficult to prepare by application of classical gold carbene chemistry.…”

Section: Reactions With Alkynesmentioning

confidence: 91%

Nitrene Chemistry in Organic Synthesis: Still in Its Infancy?

2012

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The element nitrogen is essential to life. Considerable attention is thus paid to the development of synthetic methods for its introduction into molecules. Nitrenes, long regarded as highly reactive but poorly selective species, have recently emerged as useful tools for the formation of C-N bonds. Practical metal-catalyzed protocols are now available for the preparation of amines through either the aziridination of alkenes or the C-H amination of alkanes. Recent results highlighted in this Minireview suggest that synthetic nitrene chemistry is maturing with a wider scope not limited to these two reactions.

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Intermolecular and Selective Synthesis of 2,4,5‐Trisubstituted Oxazoles by a Gold‐Catalyzed Formal [3+2] Cycloaddition

Cited by 92 publications

References 95 publications

Ynamides in Ring Forming Transformations

Ynamides in Ring Forming Transformations

Synthesis of Cyclobutanones via Gold‐Catalyzed Oxidative Rearrangement of Homopropargylic Ethers

Nitrene Chemistry in Organic Synthesis: Still in Its Infancy?

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