Mattox-Kendall reaction

What is Mattox-Kendall reaction?

The Mattox-Kendall reaction, which was first reported in 1948, involves the synthesis of α,β-unsaturated ketones by dehydrobrominating the phenylhydrazone of a semicarbazone derivative of the corresponding α-bromoketone. This reaction is also known as the Kendall synthesis or Mattox-Kendall dehydrobromination.

Mattox-Kendall reaction - general reaction scheme - Kendall synthesis - Mattox-Kendall dehydrobromination
Mattox-Kendall reaction

Mattox-Kendall reaction is commonly used to transform steroids, such as 2-bromo-3-ketoallo-steroids, 4-bromo-3-ketosteroid, 2,2-dibromo-3-ketoallosteroids, and 6-bromo-3-ketosteroids, into corresponding conjugated ketones. However, it can also be applied to other cyclic α-bromo ketones or alicyclic ketones. The intermediate hydrazone can be dehydrobrominated using pyruvate or pyruvic acid. It is essential to rigorously purify the α-bromo ketone for a high yield of the corresponding conjugated ketone. Direct dehydrobromination of α-bromo ketones using a base such as collidine does not give conjugated enone.

The Mattox-Kendall reaction does not work for 2-bromo-1-tetralone and 2-bromo-1-keto-1,2,3,4-tetrahydrophenanthrene, in which the bromo is replaced by a methoxy group upon boiling with methanol. Methyl 4β-bromo-3-ketocholanate is also not suitable for this reaction.

References

Mattox, V. R., and Kendall, E. C. (1948). The preparation of 3-keto-Δ4-steroids. Journal of the American Chemical Society, 70(2), 882-883. DOI: 10.1021/ja01182a532

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