Favorskii reaction

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Not to be confused with Favorskii rearrangement.

The Favorskii reaction is the nucleophilic attack of a terminal alkyne with acidic protons on a carbonyl group.[1] The reaction was discovered in the early 1900s by the Russian chemist Alexei Yevgrafovich Favorskii.[2][3]

Favorskii reaction and the possible subsequent rearrangement

When catalyzed by acid, this reaction is called the Meyer–Schuster rearrangement.

Reaction mechanism[edit]

A metal acetylide is formed in situ when an alkyne is treated with a strong bases such as a hydroxide or an alkoxide.[4] The metal acetylide then reacts with an aldehyde or ketone to form a propargyl alcohol. When an α-hydrogen is present (as is the case when the carbonyl is an aldehyde), it will tautomerize to the corresponding enone.[5]

Protecting group[edit]

This reaction is used to protect alkynes: the alkyne is either converted with acetone to a 2-hydroxyprop-2-yl-alkyne or a protected alkyne can be directly synthesized using the commercially available 2-methyl-3-butyn-2-ol as an the alkyne source.[6] The protective group can be removed by heating the compound in a solution of potassium hydroxide in propan-2-ol (a retro-Favorskii reaction).[7]

See also[edit]

References[edit]

  1. ^ Smith, Michael B.; March, Jerry (2007). "Chapter 16. Addition to Carbon–Hetero Multiple Bonds". March's Advanced Organic Chemistry: Reactions, Mechanisms, and Structure (6th ed.). Hoboken, New Jersey: John Wiley & Sons, Inc. pp. 1359–1360. doi:10.1002/9780470084960.ch16. ISBN 9780471720911. 
  2. ^ Favorsky, A.E. (1905). "Action of potassium hydroxide on mixtures of ketones and phenylacetylene". Zhurnal Russkago Fiziko-Khimicheskago Obshchestva. 37: 643–645. 
  3. ^ Favorsky, A.E. (1907). "Action de la potasse caustique sur les mélanges des cétones avec le phénylacétylène". Bulletin de la Société Chimique de France. 2: 1087–1088. 
  4. ^ Viehe, Heinz Günter (1969). Chemistry of Acetylenes (1st ed.). New York: Marcel Dekker, inc. pp. 225–241. doi:10.1002/ange.19720840843. 
  5. ^ Sobenina, L. N.; Tomilin, D. N.; Petrova, O. V.; Mikhaleva, A. I.; Trofimov, B. A. (2013). "Synthesis of secondary propargyl alcohols from aromatic and heteroaromatic aldehydes and acetylene in the system KOH-H2O-DMSO". Russian Journal of Organic Chemistry. 49 (3): 356–359. doi:10.1134/S107042801303007X. 
  6. ^ Kukula, H.; Veit, S.; Godt, A. (1999). "Synthesis of Monodisperse Oligo(para-phenyleneethynylene)s Using Orthogonal Protecting Groups with Different Polarity for Terminal Acetylene Units". European Journal of Organic Chemistry. 1999 (1): 277–286. doi:10.1002/(SICI)1099-0690(199901)1999:1<277::AID-EJOC277>3.0.CO;2-R. 
  7. ^ Wuts, Peter G. M.; Greene, Theodora W. (2007). "Chapter 8. Protection for the Alkynes". Greene's Protective Groups in Organic Synthesis (4th ed.). Hoboken, New Jersey: John Wiley & Sons, Inc. p. 932. doi:10.1002/9780470053485.ch8. ISBN 9780471697541.