Rearrangement of 4-imino-(1H,4H)-3,1-benzoxazine-2-ones to 2,4-quinazolinediones via an isocyanate carboxamide intermediate

Reaction of 3-arylimino-2-indolinones 1 with m-chloroperbenzoic acid in CH2Cl2 or methanol at 0°C leads to the corresponding 3-aryl-2,4(1H,3H)-quinazolinediones 4 and (2-arylcarbamoyphenyl)carbamic acid methyl ester 5, respectively. These conversions proceed through 4-arylimino-(1H,4H)-3,1-benzoxazin-2-one 2 and its ring-opened isocyanate carboxamide isomer 3 as key intermediates.