Tandem Condensation/Rearrangement Reaction of 2-Aminohetarene N-Oxides for the Synthesis of Hetaryl Carbamates
A new approach to hetaryl carbamates through a tandem condensation/rearrangement reaction of 2-aminohetarene N-oxides was developed. The developed reaction is suitable for both five- and six-membered heterocycles and proceeds through the condensation of 2-aminohetarene N-oxide with trimethyl orthoformate followed by intramolecular N-oxide oxygen transfer. For five-membered hetarene N-oxides (furoxans), the intramolecular rearrangement is catalyzed by a cyanide anion, while for six-membered hetarene N-oxides (azines), Lewis acid catalysis is sufficient. The developed protocol is characterized by operational simplicity and high efficiency, resulting in carbamoyl derivatives in good and high yields.