Double Chapman rearrangement

The Chapman rearrangement provides an elegant synthesis of unsymmetrical diarylamines that are otherwise difficult of access. When aryl JV-arylbenz-imidoates are heated, the O-aryl group migrates to nitrogen while the double bond moves from the N=C to the C=0 position. For example, 2,4,6-tri-chlorophenyl iV-(o-chlorophenyl)benzimidoate is converted quantitatively into A-(0-chlorophenyl)-jV-(2,4,6-trichlorophenyl)benzamide when heated for... 

In Zimmerman s picture of n,ir triplets of dienones undergoing skeletal rearrangements, the second double bond is essential. However, Chapman s idea of the excited state adapts itself readily to explaining the behavior of the enones. Both authors have now examined the behavior of ketone 35. Chapman finds that irradiation of an optically active sample of 35 yields a product which is almost 100% optically active.415 Zimmerman finds that the reaction can be quenched very efficiently by both naphthalene (ET = 61 kcal) and di-te/7-butylni-troxide, but only weakly by biphenyl (ET 70 kcal).416... 

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