Synthesis of o-(diphenylphosphinoyloxy)anilines by the rhodium-catalyzed reaction of nitroarenes and diphenylphosphine oxide

A rhodium complex Rh2(OAc)4 catalyzed the reaction of nitrobenzenes and diphenylphosphine oxide HP(O)Ph2 giving o-(diphenylphosphinoyloxy)anilines predominantly, which were accompanied by small amounts of the p-isomers. Nitorobenzenes possessing a bulky o-substituent, particularly o-(t-butyl)nitrobenzenes, underwent the reaction in high yields. The reaction is considered to involve the reductive formation of O-phosphinoyl-N-arylhydroxyamines from nitrobenzenes, and o-phosphinoyloxylation by the rearrangement.