Hofmann-Martius rearrangement

The Hofmann-Martius rearrangement in organic chemistry is a rearrangement reaction converting an N-alkylated aniline to the corresponding ortho and / or para aryl-alkylated aniline. The reaction requires heat and the catalyst is an acid like hydrochloric acid ^{[1] [2]}

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When the catalyst is a metal halide the reaction is also called the Reilly-Hickinbottom rearrangement ^[3].

The reaction is also known to work for aryl ethers and two conceptually related reactions are the Fries rearrangement and the Fischer-Hepp rearrangement. Its reaction mechanism centers around dissociation of the reactant with the positively charged organic residue R attacking the aniline ring in a Friedel-Crafts alkylation.

In one study this rearrangement is applied to a 3-N(CH₃)(C₆H₅)-2-oxindole ^{[4] [5]}:

References

1. ^ Hofmann, A. W.; Martius, C. A. Ber 1871 4, 742-748.
2. ^ Hofmann, A. W. Ber 1872, 5, 720-722.
3. ^ Reilly, J.; Hickinbottom, W. J. J. Chem.Soc. 1920, 103-137
4. ^ Thermal and Acid-Catalyzed Hofmann-Martius Rearrangement of 3-N-Aryl-2-oxindoles into 3-(Arylamino)-2-oxindoles Philip Magnus and Rachel Turnbull Org. Lett.; 2006; 8(16) pp 3497 - 3499; (Letter) doi:10.1021/ol061191z
5. ^ heating 1 in toluene at 80°C gives 30% 2-o (ortho) and 37% 2-p (para)