Amination, Acetamidation, and Amidation of Substituted Aromatic Carbamates in Polyphosphoric Acid.

Electrophilic amination of methyl N-(hydroxyphenyl)carbamates and methyl N-(4-methoxyphenyl)carbamate with sodium azide in 86% polyphosphoric acid (PPA) at 55–60°C regioselectively afforded methyl N-(3-amino-2-hydroxyphenyl)-, N-(4-amino-3-hydroxyphenyl)-, N-(3-amino-4-hydroxyphenyl)-, and N-(3-amino-4-methoxyphenyl)carbamates, i.e., the amino group entered the ortho position with respect to the hydroxy or methoxy group. The reactions of methyl N-(4-methoxyphenyl)carbamate with nitromethane and nitroethane in 80% PPA at 95–110°C gave methyl N-(3-carbamoyl-4-methoxyphenyl)carbamate and methyl N-(3-acetamido-4-methoxyphenyl)carbamate, respectively. Methyl N-[4-(N′-hydroxyethanimidamido)phenyl]carbamate was obtained by reaction of 4-[(methoxycarbonyl)amino]benzoic acid with excess nitroethane in 86% PPA at 125°C. [ABSTRACT FROM AUTHOR]