Sonn-Müller reaction

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The Sonn-Müller reaction (also known as the Sonn-Müller method) is a name reaction in organic chemistry that was first described in 1919 and is named after its discoverers Adolf Sonn (1867–1942) and Ernst Müller (1881–1945).

Overview reaction

Aromatic anilides are converted into aromatic aldehydes with phosphorus pentachloride , tin (II) chloride , dilute hydrochloric acid and water :

Sonn-Müller reaction, overview reaction

Reaction mechanism

In the first step, an addition reaction of the phosphorus pentachloride to the anilide 1 takes place. This results in the formation of intermediate 2 . Then the central, positively polarized carbon atom is attacked by the chloride anion, which creates compound 3 . By eliminating one molecule of hydrochloric acid and one molecule of phosphorus oxychloride , the imidoyl chloride 4 is formed:

Sonn-Müller reaction, reaction mechanism a

4 is now reduced with tin (II) chloride . The tin cation transfers an electron to the chlorine atom. Another electron from the bond between the carbon and chlorine atom is assigned to the chlorine atom. The resulting chloride anion coordinates to the formally positively charged tin cation, so that the radical 5 and tin (III) chloride are formed. Another electron transfer from the tin cation to the radical causes the formation of the carbanion 6 .

Sonn-Müller reaction, reaction mechanism b

The carbanion 6 is protonated using dilute hydrochloric acid . The resulting chloride anion coordinates to the tin salt. Tin (IV) chloride is a waste product. The resulting imine 7 is now split hydrolytically via structure 8 .

Sonn-Müller reaction, reaction mechanism c

In the example chosen , benzaldehyde 11 is formed as the main product in addition to the aniline salt 10 . By choosing other aryl radicals , other aromatic aldehydes can be obtained.

Practical meaning

Because of the many possibilities for synthesizing carbonyl compounds , the Sonn-Müller reaction did not acquire any major preparative importance. Yet it has been used over and over again throughout history. Compared to the reduction of carboxylic acid chlorides , it is only advantageous if the anilide is easily accessible. Shortly after the discovery of the reaction, anilides became more accessible through the Friedel-Crafts acylation of isocyanates with aromatics, making the synthesis of certain aromatic aldehydes cheaper. These were often of importance in the field of odor chemistry. From a medical point of view, it is worth mentioning the contribution of the reaction to the synthesis of anesthetics.

literature

  • Z. Wang: Comprehensive Organic Name Reactions and Reagents , Vol 2. John Wiley & Sons, Hoboken, New Jersey 2009 , pp. 2625-2627, ISBN 978-0-471-70450-8 .
  • A. Ingendoh, J. Falbe (Ed.): Methods of organic chemistry: Aldehydes. Extension and subsequent volumes , Vol 4. Georg Thieme Verlag, Stuttgart, New York 1983 , p. 473, ISBN 3-13-217304-5 .

Individual evidence

  1. ↑ F. Effenberger, R. Gleiter: Synthesis of substituted benzoic acids, benzonitriles and benzaldehydes , Chemical Reports 1964 , 97 , pp. 480–482, doi : 10.1002 / cber.19640970223 .
  2. ↑ A. Sonn, E. Müller: About a new method for converting carboxylic acids into aldehydes , reports of the German chemical society 1919 , 52 , pp. 1927-1934, doi : 10.1002 / cber.19190521002 .
  3. ^ PE Papadakis, W. Boand: Synthesis of 5- (2 ', 3', 4'-trimethoxyphenyl) -4,6-dicarbethoxycyclohexanedione-1,3 and Derivatives , Journal of Organic Chemistry 1960 , pp. 2075-2077, doi : 10.1021 / jo01065a096 .
  4. ↑ TS Work: 80. The synthesis of amines from amides through the amidodichlorides , Journal of the Chemical Society 1942 , pp. 429-432, doi : 10.1039 / JR9420000429 .
  5. ↑ LF Fieser, LM Joshel: 5-Methylchrysene , Journal of the American Chemical Society 1940 , pp 1211-1214, doi : 10.1021 / ja01862a064 .
  6. ↑ J. v. Braun, W. Rudolph: Amide and imide chlorides of non-aromatic acids, Part VIII: Presentation of α, β-unsaturated aldehydes , reports of the German chemical society 1934 , 67 , pp. 269–281, doi : 10.1002 / cber.19340670223 .
  7. ^ RC Roberts, TB Johnson: The preparation of derivatives of diphenic acid possessing the properties of local anesthetics , Journal of the American Chemical Society 1925 , pp. 1396-1402, doi : 10.1021 / ja01682a026 .