Catalytic Ring Expansion Adventures

Njardarson, Jón T.

doi:10.1055/s-0032-1318326

Cited by 38 publications

(13 citation statements)

References 44 publications

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“…(1–6) The aziridine structural motif, predominantly N-H and to a lesser extent N-alkyl, also appears in biologically active natural products (e.g., azinomycins and mitomycins). (7–9) As a result, the synthesis and chemistry of aziridines have been the subject of intense research during the past 25 years, resulting in multiple aziridination methods.…”

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confidence: 99%

“…Indeed, 3b was cleanly amino-oxyarylated in TFE and 4b was isolated in 66% yield. It was unclear if the transformation 3b → 4b involved the opening of a highly reactive aziridine (6) or an alternative process. Surprisingly, when 7 was reacted in trifluoroethanol as solvent, cis-N -H aziridine 8 was isolated in excellent yield (83%) instead of the expected amino-oxyarylated product.…”

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confidence: 99%

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Direct Stereospecific Synthesis of Unprotected N-H and N-Me Aziridines from Olefins

Jat

Paudyal

Gao

et al. 2014

Science

282

217

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Despite the prevalence of the N-H aziridine motif in bioactive natural products and the clear advantages of this unprotected parent structure over N-protected derivatives as a synthetic building block, no practical methods have emerged for direct synthesis of this compound class from unfunctionalized olefins. Here, we present a mild, versatile method for the direct stereospecific conversion of structurally diverse mono-, di-, tri- and tetra-substituted olefins to N-H aziridines using O-(2,4-dinitrophenyl)hydroxylamine (DPH) via homogeneous rhodium catalysis with no external oxidants. This method is operationally simple (i.e., one-pot), scalable and fast at ambient temperature, furnishing N-H aziridines in good-to-excellent yields. Likewise, N-alkyl aziridines are prepared from N-alkylated DPH derivatives. Quantum-mechanical calculations suggest a plausible Rh-nitrene pathway.

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confidence: 99%

mentioning

confidence: 99%

Direct Stereospecific Synthesis of Unprotected N-H and N-Me Aziridines from Olefins

Jat

Paudyal

Gao

et al. 2014

Science

282

217

View full text Add to dashboard Cite

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“…Aziridines are highly reactive molecules that serve as useful synthetic intermediates in several chemical transformations (Figure ). They can be converted into β‐amino alcohols or vicinal diamines, amongst others, through S N 2 ring‐opening reactions …”

Section: Introductionmentioning

confidence: 99%

Unprotected Aziridines: A Synthetic Overview

2017

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Unprotected (NÀH) aziridines are the key components in several biologically active natural products and important buildingb locks in organic synthesis. However,t he synthesis of unprotecteda ziridines is much more difficult than their oxygen counterparts (epoxides). Therefore, the development of efficient routes for their synthesis represents an attractive task fororganic chemists and, as aresult, avariety of methods have been developed. In this Focus Review, we have described the various approaches that have been reportedf or the synthesis of NH-aziridines.

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“…Thiiranes [1][2][3][4][5][6][7][8] and thietanes [9][10][11][12][13][14][15][16][17][18][19] are important intermediates in organic synthesis, just as their three-and four-membered oxygen and nitrogen analogs (oxiranes and aziridines, and oxetanes and azetidines) [20][21][22][23][24][25][26]. They have been widely applied in the preparation of sulfur-containing compounds, such as diverse thiols, thioethers, and ring-expansion products, via ring-opening reactions, isomerizations, insertions, and ring openings followed by intramolecular cyclization.…”

Section: Introductionmentioning

confidence: 99%

Synthesis of Four- to Seven-Membered Heterocycles by Ring Expansion: Ring Expansions of Thiiranes and Thietanes

2015

Topics in Heterocyclic Chemistry

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Thiiranes and thietanes are important intermediates in organic synthesis, just as their oxygen and nitrogen analogs (oxiranes and aziridines, and oxetanes and azetidines). They have been widely applied in the preparation of sulfur-containing compounds. Thiiranes undergo ring expansions to generate various four-, five-, six-, and seven-membered heterocyclic products, even larger heterocycles. Thietanes also undergo ring expansions to produce five-, six-, and seven-membered heterocyclic compounds, even larger heterocycles as well. The ring expansions include insertion, nucleophilic and electrophilic ring opening, and subsequent cyclization. The regioselectivities in nucleophilic ring-opening reactions of unsymmetrical thiiranes and thietanes are discussed. Generally, nucleophiles attack on the less substituted vicinal carbon atom to the sulfur in unsymmetrical thiiranes and thietanes, controlled by steric hindrance. In the presence of Lewis acids, the electronic effect significantly impacts the regioselectivity in ring-opening reactions. 2-Arylthiiranes and 2-alkenylthiiranes are attacked on their more substituted vicinal carbon atom with nucleophiles (the electronic effect control). For thietanes, electrophilic ring expansion is one of the major processes. Unsymmetrical thietanes undergo electrophilic ring expansion with carbenes and nitrenes through electrophilic attack and subsequent Stevens-type rearrangement, with the more substituted vicinal carbon shifting. Mechanisms on some of the most important ring expansions of thiiranes and thietanes are introduced.

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Catalytic Ring Expansion Adventures

Cited by 38 publications

References 44 publications

Direct Stereospecific Synthesis of Unprotected N-H and N-Me Aziridines from Olefins

Direct Stereospecific Synthesis of Unprotected N-H and N-Me Aziridines from Olefins

Unprotected Aziridines: A Synthetic Overview

Synthesis of Four- to Seven-Membered Heterocycles by Ring Expansion: Ring Expansions of Thiiranes and Thietanes

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