Reimer-Tiemann reaction

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The Reimer-Tiemann reaction is a name reaction in organic chemistry . The key reaction was discovered by Karl Reimer and researched more intensively by Ferdinand Tiemann . The Reimer-Tiemann reaction is the reaction of phenols with dichlorocarbene , which is formed from chloroform in an alkaline solution at a higher temperature and is very unstable. The ortho - formylation product is then predominantly obtained, while other formylation reactions, such as the Gattermann synthesis , predominantly yield the para -product.

Overview of the Reimer-Tiemann reaction

mechanism

First of all, the dichlorocarbon must be obtained for the reaction. For this purpose, reacts chloroform 1 first with the base via the carbanion 2 to dichlorocarbene ( 3 ) ( singlet - carbene ). In the process, chloroform is deprotonated and then splits off a chloride ion .

Mechanism 1 Reimer-Tiemann reaction

Now the dichlorocarbene is reacted with phenol. Phenol 4 is present as phenolate 5 under the reaction conditions . The dichlorocarbene ( 3 ) attaches to the mesomeric phenolate anion in the ortho position to form 6 . From the primary product 6 is produced by proton migration the carbanion 7 . After a chloride ion has been split off and a subsequent rearomatization, the resulting carbenium ion 9 is hydrolyzed and the phenolate anion 11 is obtained. After further elimination of chloride ions , a dienone 12 is formed , which tautomerizes to the aromatic end product 13 after a dienone-phenol rearrangement .

Mechanism 2 Reimer-Tiemann reaction

The yield of the reaction is generally below 50%, so it is rarely used. Their advantage lies in their ortho selectivity. The reaction can be favorably influenced by ultrasound, the reaction time is shortened and the yield increases.

literature

  • Hans Wynberg: The Reimer-Tiemann Reaction. In: Chemical Reviews . Vol. 60, No. 2, 1960, pp. 169-184, doi : 10.1021 / cr60204a003 .
  • Hans Wynberg, Egbert W. Meijer: The Reimer-Tiemann Reaction. In: Organic Reactions . Vol. 28, No. 1, 1982, pp. 1-36, doi : 10.1002 / 0471264180.or028.01 .
  • Hans Wynberg: The Reimer-Tiemann Reaction. In: Barry M. Trost, Ian Fleming: Comprehensive Organic Synthesis. Selectivity, Strategy & Efficiency in Modern Organic Chemistry. Volume 2: Additions to C - X π-bonds. Part 2. Pergamon Press, Oxford et al. 1991, ISBN 0-08-040593-2 , pp. 769-775.

Individual evidence

  1. ↑ K. Reimer: About a new mode of formation of aromatic aldehydes. In: Reports of the German Chemical Society . Volume 9, No. 1, 1876, pp. 423-427, ( digitized version ).
  2. ↑ K. Reimer, F. Tiemann: About the action of chloroform on alkaline phenolates. In: Reports of the German Chemical Society. Volume 9, No. 1, 1876, pp. 824-828, ( digitized ). - K. Reimer, F. Tiemann: On the action of chloroform on alkaline phenols and especially aromatic oxyacids in alkaline solution. In: Reports of the German Chemical Society. Volume 9, No. 2, 1876, pp. 1268-1278, ( digitized ). - K. Reimer, F. Tiemann: On the action of carbon tetrachloride on phenol in alkaline solution (formation of salicylic acid and paroxybenzoic acid). In: Reports of the German Chemical Society. Volume 9, No. 2, 1876, pp. 1285-1287, ( digitized ).
  3. ^ Zerong Wang: Comprehensive Organic Name Reactions and Reagents. Volume 3. Wiley, Hoboken NJ 2009, ISBN 978-0-470-53346-8 , p. 2329.