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Aza-Wittig reaction

From Wikipedia, the free encyclopedia

The Aza-Wittig reaction or is a chemical reaction of a carbonyl group with an aza-ylide, also known as an iminophosphorane (R3P=NR'). Aza-Wittig reactions are most commonly used to convert aldehydes and ketones to the corresponding imines.[1] The conversion has also been practiced in an intramolecular sense, which is commonly used in the synthesis of N-heterocyclic compounds.[2]

Reaction mechanism

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The mechanism of the aza-Wittig reaction is analogous to that of the Wittig reaction, with the Wittig reagent replaced by an iminophosphorane.[1]

Mechanism of Aza-Wittig-reaction

In some cases, the iminophosphorane is not isolated but generated in situ. In this manifestation, the phosphine, carbonyl, and organic azide are combined

Scope and limitations

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Besides preparing imines from aldehydes and ketones, the aza-Wittig-reaction can also convert carbon dioxide to isocyanates, carbon disulfide to organic thiocyanates, and isocyanates to carbodiimides.[1][3]

There exists solid-supported modifications of the reaction.[4][1][5]

Similar to the Wittig reaction, the reaction suffers from issues with triphenylphosphine oxide by-product removal. Such an issue is mitigated via catalytic aza-Wittig-reactions, some of which entail elements other than phosphorus, like arsenic and tellurium[5][6].

History

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The reagent for the aza-Wittig reaction, iminophosphorane, was discovered in 1919 by Hermann Staudinger. The reaction itself was discovered thirty years later.[3]

Examples

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An example of the aza-Wittig-reaction being utilized in organic synthesis is the synthesis of (–)-benzomalvin A. Two intramolecular aza-Wittig-reactions were used to construct the seven-membered ring and the six-membered ring in the molecule's skeleton.[1]

Synthesis of (−)-Benzomalvin A via multiple aza-Wittig-reactions

See also

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References

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  1. ^ a b c d e Kurti 1 Czako 2, Laszlo 1 Barbara 2 (15 September 2005). Strategic Applications of Named Reactions in Organic Synthesis. Elsevier. pp. 24–25. ISBN 0-12-429785-4.{{cite book}}: CS1 maint: numeric names: authors list (link)
  2. ^ Wamhoff, Heinrich; Richardt, Gabriele; Stölben, Stephan (1995-01-01), Katritzky, Alan R. (ed.), Iminophosphoranes: Versatile Tools in Heterocyclic Synthesis, Advances in Heterocyclic Chemistry, vol. 64, Academic Press, pp. 159–249, doi:10.1016/s0065-2725(08)60172-5, ISBN 978-0-12-020764-0, retrieved 2024-05-24
  3. ^ a b "Aza-Wittig Reaction". 15 March 2015. Retrieved 2024-05-24.
  4. ^ Hemming, Karl; Bevan, Matthew J.; Loukou, Christina; Patel, Snahal D.; Renaudeau, Denis (2001-02-20). "ChemInform Abstract: A One-Pot Aza-Wittig Based Solution and Polymer-Supported Route to Amines". ChemInform. 32 (8). doi:10.1002/chin.200108116. ISSN 0931-7597.
  5. ^ a b Lao, Zhiqi; Toy, Patrick H (2016-11-30). "Catalytic Wittig and aza-Wittig reactions". Beilstein Journal of Organic Chemistry. 12: 2577–2587. doi:10.3762/bjoc.12.253. ISSN 1860-5397. PMC 5238588. PMID 28144327.
  6. ^ Li, Huaifeng; Lupp, Daniel; Das, Pradip K.; Yang, Li; Gonçalves, Théo P.; Huang, Mei-Hui; El Hajoui, Marwa; Liang, Lan-Chang; Huang, Kuo-Wei (2021-04-02). "Redox-Neutral Imination of Alcohol with Azide: A Sustainable Alternative to the Staudinger/Aza-Wittig Reaction". ACS Catalysis. 11 (7): 4071–4076. doi:10.1021/acscatal.1c00379. hdl:10754/668169. ISSN 2155-5435.
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