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21.1.5.5 Method 5: Chapman Rearrangement from Aryl Imidates

DOI: 10.1055/sos-SD-021-00115

Judd, W. R.; Katz, C. E.; Aubé, J.Science of Synthesis, (200521162.

The thermal conversion of N,N-diaryl imidates into N,N-diaryl amides is known as the Chapman rearrangement (Scheme 38).[‌89‌] Although the reaction was discovered by Mumm, Hesse, and Volquartz in 1915, its name is derived from the chemist who studied the mechanism and first applied the rearrangement to a general synthesis of diphenyl­amines.[‌90‌] Mono-, di-, and trialkyl-substituted imidates can also undergo the rearrangement; however, reaction with these substrates requires catalysis by sulfuric acid, iodo­methane, or methyl sulfate, and occurs by a distinctly different mechanism to that of the classical Chapman rearrangement of aryl imidates. In many cases, the rearrangement requires heating of the aryl imidate to a high temperature (280300°C), either neat or in the presence of solvent. Refluxing in tetraethylene glycol dimethyl ether (tetraglyme; bp 276°C) is optimal for many rearrangements.[‌91‌]

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