N-Aryl-2-nitrosoanilines, available from the reaction of nitroarenes with anilide anions, undergo cyclization to furnish substitutedphenazines. The reaction is promoted by potassium carbonate in methanol, N,O-bis(trimethylsilyl)acetamide (BSA) in aprotic solvents, and by acetic acid. The method is illustrated by the synthesis of 1-methoxyphenazine, a precursor of pyocyanine, starting from the appropriate
A Short Preparation of Pyrroloquinoxalinones via a Cascade Reaction of N-Aryl-5-alkylamino-2-nitrosoanilines with Methyl 2-Cyanoalkanoates: Unexpected Direction of Nucleophilic Substitution of Hydrogen
N-Aryl-2-nitrosoanilines possessing 5-alkylamino groups undergo a bisheteroannulation reaction with anions of 2-cyanoalkanecarboxylates resulting in pyrroloquinoxalinone derivatives. The cascade reaction involves condensation of the cyanoester anions with the nitroso group, unusual nucleophilic substitution of hydrogen in the nitrosoaniline-derived intermediate with the second carbanion molecule, and double intramolecular acylation of the amino functions.