An efficient, base‐induced rearrangement of 2‐[(1,2‐dioxo‐2‐(methylamino)ethyl)phenylamino]benzoic acid methyl ester (7a) to the isomeric 2‐[(1,2‐dioxo‐2‐(phenylamino)ethyl)methylamino]benzoic acid methyl ester (27a) is described. This novel rearrangement must proceed through a spiro intermediate wherein benzoate is acting as a Michael receptor. When 2‐[(1,2‐dioxo‐2‐(methylamino)ethyl)methylamino]benzoic acid methyl ester (28)‐an oxamide which would produce a degenerate spiro intermediate — was subjected to rearrangement conditions, the product obtained was 1,3‐dimethyl‐2,4‐(1H,3H)quinazolinedione (29). This latter transformation may have proceeded via a benzodiazepinetrione intermediate.
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Peet et al. (1980) studied this question.
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