Kutscherov reaction

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The Kutscherov reaction is a name reaction of organic chemistry and named after the Russian chemist Mikhail Kutscherow . The reaction allows the synthesis of aldehydes or ketones from alkynes .

Overview reaction

In the reaction, water is added to the C≡C triple bond of an alkyne - ethyne in the example - catalyzed by mercury sulfate and dilute sulfuric acid. Acetaldehyde is formed :

Kutscherov overview reaction

Analogously, starting from z. B. 2-butyne by water addition 2-butanone , a ketone.

General

This reaction was documented for the first time by Fittig and Schrohe in 1875 . In 1881 it was further developed by Kutscheroff. It was previously commonly used to make ketones from longer-chain alkynes such as butenine and propyne . In addition, acetaldehyde was commercially produced from ethine using the same procedure . During production, yields of 79.8% could be achieved at relatively low temperatures of ~ 125 ° C.

Proposed reaction mechanism

During the reaction, the alkyne forms a coordinative bond with the mercury cation and the short-lived π complex 2 is formed . The regioselectivity of the water is determined by the two radicals R 1 and R 2 (H, alkyl radicals, methyl radicals) by mesomerism , since these influence the stability of the now partially positively charged carbon. By the accumulation of the water, an H + is split off from the water and the electron pair loosened by the mercury forms a bond with the mercury. The result is structure 3 . The double bond of the alkene now attacks an H + cation and a carbocation 4 forms as a transition state on the oxygen side , from which ketone 5 is formed by splitting off the proton from the hydroxyl group and shifting electrons . The addition of another proton to one of the lone pairs of electrons in oxygen creates intermediate stage 6 . The electron pair to the positively charged oxygen is turned over and thus the bond from mercury to the positive carbocation that has been created again is turned over. Mercury sulphate is split off again and we get enol 7 . Due to the keto-enol tautomerism , the ketone 8 is then formed .

Reaction mechanism of the Kutscherov reaction

literature

  • Journal of the American Chemical Society 1990, 112, pp. 6291-6296.
  • Kutscheroff, MG, Reports of the German Chemical Society, 1881, 14, p. 1532 u. 1540.
  • Zerong Wang: Comprehensive Organic Name Reactions and Reagents , Volume 2, Wiley, 2009, pp. 1710-1712, ISBN 978-0-471-70450-8 .

Individual evidence

  1. Fittig, R. and Schrohe, A., Reports of the German Chemical Society (since about 1930 "Chemical Reports"), 1875, 8, p. 367.
  2. ^ Kutscheroff, MG: Reports of the German Chemical Society . tape 14 , 1881, p. 1532 and 1540 , doi : 10.1002 / cber.188101401319 .
  3. (a) Conway, RF, US Pat., July 24, 1934, 1, 967, p. 225. (b) Carter, AS, US Pat., Feb. 7, 1933, 1, 896, p. 161.
  4. Kutscheroff, MG, Reports of the German Chemical Society 1884, 17, p. 13.
  5. Thomas, RJ, Campbell, KN and Hennion, GF, Journal of the American Chemical Society, 1938, 60, p. 718.
  6. ^ Zerong Wang: Comprehensic Organic Name Reactions and Reagents , Volume 2, Wiley, 2009, p. 1711, ISBN 978-0-471-70450-8 .
  7. Thomas Klemens Kribber: Ruthenium-catalyzed hydration of terminal alkynes and their use in synthesis strategies , Dissertation RWTH Aachen University, 2009 http://publications.rwth-aachen.de/record/51262/files/Kribber_Thomas.pdf p. 4.
  8. ^ Zerong Wang: Comprehensic Organic Name Reactions and Reagents , Volume 2, Wiley, 2009, pp. 1710–1712, ISBN 978-0-471-70450-8 .
  9. ^ Bradford P. Mundy, Michael G. Ellerd, Frank G. Favaloro Jr .: Name Reactions and Reagents in Organic Syntheses , 2nd Edition, Wiley-Interscience, 2005, p. 384 and p. 474, ISBN 0-471-22854 -0 .